業績情報

• Boundary driven turbulence on string worldsheet
  Takaaki Ishii; Keiju Murata; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2024, 号：1, 2024年01月, ［査読有り］
  Abstract
  
  We study the origin of turbulence on the string worldsheet with boundaries laid in anti de Sitter (AdS) spacetime. While the classical motion of a single closed string in AdS is integrable, it has recently been recognized that weak turbulence arises in the case of an open string suspended from the AdS boundary. In the open string case, it is necessary to impose boundary conditions on the worldsheet boundaries. We classify which boundary conditions preserve integrability. Based on this classification, we anticipate that turbulence may occur on the string worldsheet if integrability is not guaranteed by the boundary conditions. Numerical investigations of the classical open-string dynamics support that turbulence occurs when the boundary conditions are not integrable.
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep01(2024)073
  DOI ID：10.1007/jhep01(2024)073, eISSN：1029-8479
• Chaotic string motion in a near pp-wave limit
  Shodai Kushiro; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2023, 号：1, 2023年01月, ［査読有り］
  Abstract
  
  We revisit classical string motion in a near pp-wave limit of AdS₅ × S⁵. It is known that the Toda lattice models are integrable. But if the exponential potential is truncated at finite order, then the system may become non-integrable. In particular, when the exponential potential in a three-particle periodic Toda chain is truncated at the third order of the dynamical variables, the resulting system becomes a well-known non-integrable system, Henon-Heiles model. The same thing may happen in a near pp-wave limit of AdS₅ × S⁵, on which the classical string motion becomes chaotic.
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep01(2023)065
  DOI ID：10.1007/jhep01(2023)065, eISSN：1029-8479
• Chaotic instability in the BFSS matrix model
  Osamu Fukushima; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2022, 号：9, 2022年09月, ［査読有り］
  Abstract
  
  Chaotic scattering is a manifestation of transient chaos realized by the scattering with non-integrable potential. When the initial position is taken in the potential, a particle initially exhibits chaotic motion, but escapes outside after a certain period of time. The time to stay inside the potential can be seen as lifetime and this escape process may be regarded as a kind of instability. The process of this type exists in the Banks-Fischler-Shenker-Susskind (BFSS) matrix model in which the potential has flat directions. We discuss this chaotic instability by reducing the system with an ansatz to a simple dynamical system and present the associated fractal structure. We also show the singular behavior of the time delay function and compute the fractal dimension. This chaotic instability is the basic mechanism by which membranes are unstable, which is also common to supermembranes at quantum level.
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep09(2022)039
  DOI ID：10.1007/jhep09(2022)039, eISSN：1029-8479
• Non-Abelian Toda field theories from a 4D Chern-Simons theory
  Osamu Fukushima; Jun-ichi Sakamoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2022, 号：3, 2022年03月, ［査読有り］
  Abstract
  
  We derive non-abelian Toda field theories (NATFTs) from a 4d Chern-Simons (CS) theory with two order defects by employing a certain asymptotic boundary condition. The 4d CS theory is characterized by a meromorphic 1-form ω. We adopt ω with two simple poles and no zeros, and each of the order defects is located at each pole. As a result, an anisotropy parameter β² can be identified with the distance between the two defects. As examples, we can derive the (complex) sine-Gordon model and the Liouville theory.
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep03(2022)158
  DOI ID：10.1007/jhep03(2022)158, eISSN：1029-8479
• Burgers equation vs. large N limit in TT¯-deformed O(N) vector model　　　　　　　　　　　　　　　
  Junichi Haruna; Katsuta Sakai; Kentaroh Yoshida
  Nuclear Physics B, 巻：971, 2021年10月, ［査読有り］
  We study a TT¯-deformed O(N) vector model, which is classically equivalent to the Nambu-Goto action with static gauge. The thermal free energy density can be computed exactly by using the Burgers equation as a special property of TT¯-deformation. The resulting expression is valid for an arbitrary value of N. One may consider a large N limit while preserving this expression. We try to derive this result in the field-theoretical approach directly by employing the large N limit. As a result, the leading contribution coincides with the exact one. That is, the 1/N corrections are canceled out through a non-trivial mechanism.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2021.115499
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  DOI ID：10.1016/j.nuclphysb.2021.115499, ISSN：0550-3213, SCOPUS ID：85111483260
• Integrable deformed T1,1 sigma models from 4D Chern-Simons theory
  Osamu Fukushima; Jun-ichi Sakamoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2021, 号：9, 2021年09月, ［査読有り］
  Abstract
  
  Recently, a variety of deformed T^1,1 manifolds, with which 2D non-linear sigma models (NLSMs) are classically integrable, have been presented by Arutyunov, Bassi and Lacroix (ABL) [46]. We refer to the NLSMs with the integrable deformed T^1,1 as the ABL model for brevity. Motivated by this progress, we consider deriving the ABL model from a 4D Chern-Simons (CS) theory with a meromorphic one-form with four double poles and six simple zeros. We specify boundary conditions in the CS theory that give rise to the ABL model and derive the sigma-model background with target-space metric and anti-symmetric two-form. Finally, we present two simple examples 1) an anisotropic T^1,1 model and 2) a G/H λ-model. The latter one can be seen as a one-parameter deformation of the Guadagnini-Martellini-Mintchev model.
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep09(2021)037
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  DOI ID：10.1007/jhep09(2021)037, eISSN：1029-8479, SCOPUS ID：85114435321
• Chaotic string dynamics in deformed T ^1,1　　　　　　　　　　　　　　　
  Takaaki Ishii; Shodai Kushiro; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2021, 号：5, 2021年05月, ［査読有り］
  Recently, Arutyunov, Bassi and Lacroix have shown that 2D non-linear sigma model with a deformed T1,1 background is classically integrable [arXiv:2010.05573 [hep-th]]. This background includes a Kalb-Ramond two-form with a critical value. Then the sigma model has been conjectured to be non-integrable when the two-form is off critical. We confirm this conjecure by explicitly presenting classical chaos. With a winding string ansatz, the system is reduced to a dynamical system described by a set of ordinary differential equations. Then we find classical chaos, which indicates non-integrability, by numerically computing Poincaré sections and Lyapunov spectra for some initial conditions.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP05(2021)158
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  DOI ID：10.1007/JHEP05(2021)158, eISSN：1029-8479, SCOPUS ID：85119057441
• Faddeev-Reshetikhin model from a 4D Chern-Simons theory　　　　　　　　　　　　　　　
  Osamu Fukushima; Jun ichi Sakamoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2021, 号：2, 2021年02月, ［査読有り］
  We derive the Faddeev-Reshetikhin (FR) model from a four-dimensional Chern-Simons theory with two order surface defects by following the work by Costello and Yamazaki [arXiv:1908.02289]. Then we present a trigonometric deformation of the FR model by employing a boundary condition with an R-operator of Drinfeld-Jimbo type. This is a generalization of the work by Delduc, Lacroix, Magro and Vicedo [arXiv:1909.13824] from the disorder surface defect case to the order one.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP02(2021)115
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  DOI ID：10.1007/JHEP02(2021)115, eISSN：1029-8479, SCOPUS ID：85100932802
• Yang–Baxter deformations and generalized supergravity—a short summary　　　　　　　　　　　　　　　
  Orlando, Domenico; Susanne Reffert; Junichi Sakamoto; Yuta Sekiguchi; Kentaroh Yoshida
  J.Phys.A, 巻：53, 号：44, 開始ページ：443001, 終了ページ：443001, 2020年10月, ［査読有り］
  Integrable deformations of type IIB superstring theory on AdS5 × S5 have played an important role over the last years. The Yang–Baxter deformation is a systematic way of generating such integrable deformations. Since its introduction, this topic has seen important conceptual progress and has among others led to the intriguing discovery generalized supergravity, a new low-energy effective theory. This review endeavors to not only introduce the historical development of the Yang–Baxter deformation, but also its relation to generalized supergravity, non-geometric backgrounds, non-abelian T-duality and preserved Killing spinors. We supplement the general treatment with a wealth of explicit examples.
  DOI：https://doi.org/10.1088/1751-8121/abb510
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  DOI ID：10.1088/1751-8121/abb510, ISSN：1751-8113, eISSN：1751-8121, ORCID：82638151, arXiv ID：arXiv:1912.02553, SCOPUS ID：85095823247
• Yang-Baxter deformations of the AdS₅×S⁵ supercoset sigma model from 4D Chern-Simons theory　　　　　　　　　　　　　　　
  Osamu Fukushima; Jun ichi Sakamoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2020, 号：9, 2020年09月, ［査読有り］
  We present homogeneous Yang-Baxter deformations of the AdS5×S5 supercoset sigma model as boundary conditions of a 4D Chern-Simons theory. We first generalize the procedure for the 2D principal chiral model developed by Delduc et al. [5] so as to reproduce the 2D symmetric coset sigma model, and specify boundary conditions governing homogeneous Yang-Baxter deformations. Then the conditions are applicable for the AdS5×S5 supercoset sigma model case as well. In addition, homogeneous bi-Yang-Baxter deformation is also discussed.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP09(2020)100
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  DOI ID：10.1007/JHEP09(2020)100, eISSN：1029-8479, SCOPUS ID：85091573021
• Comments on η-deformed principal chiral model from 4D Chern-Simons theory　　　　　　　　　　　　　　　
  Osamu Fukushima; Jun ichi Sakamoto; Kentaroh Yoshida
  Nuclear Physics B, 巻：957, 2020年08月, ［査読有り］
  We study η-deformations of principal chiral model (PCM) from the viewpoint of a 4D Chern-Simons (CS) theory. The η-deformed PCM has originally been derived from the 4D CS theory by Delduc, Lacroix, Magro and Vicedo [arXiv:1909.13824]. The derivation is based on a twist function in the rational description. On the other hand, we start with a twist function in the trigonometric description and discuss possible boundary conditions. We show that a certain boundary condition reproduces the usual η-deformed PCM and another one leads to a new kind of Yang-Baxter deformation.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2020.115080
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  DOI ID：10.1016/j.nuclphysb.2020.115080, ISSN：0550-3213, SCOPUS ID：85086164141
• TT¯-deformation and Liouville gravity　　　　　　　　　　　　　　　
  Suguru Okumura; Kentaroh Yoshida
  Nuclear Physics B, 巻：957, 2020年08月, ［査読有り］
  We consider a gravitational perturbation of the Jackiw-Teitelboim (JT) gravity with an arbitrary dilaton potential and study the condition under which the quadratic action can be seen as a TT¯-deformation of the matter action. As a special case, the flat-space JT gravity discussed by Dubovsky et al. [arXiv:1706.06604] is included. Another interesting example is a hyperbolic dilaton potential. This case is equivalent to a classical Liouville gravity with a negative cosmological constant and then a TT¯-deformation of the matter action with a finite coupling is realized as a gravitational perturbation on AdS2.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2020.115083
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  DOI ID：10.1016/j.nuclphysb.2020.115083, ISSN：0550-3213, SCOPUS ID：85086368923
• Large N analysis of TT¯ -deformation and unavoidable negative-norm states　　　　　　　　　　　　　　　
  Junichi Haruna; Takaaki Ishii; Hikaru Kawai; Katsuta Sakai; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2020, 号：4, 2020年04月, ［査読有り］
  We study non-perturbative quantum aspects of TT¯ -deformation of a free O(N) vector model by employing the large N limit. It is shown that bound states of the original field appear and inevitably become negative-norm states. In particular, the bound states can be regarded as the states of the conformal mode in a gravitational theory, where the Liouville action is induced with the coefficient proportional to the minus of central charge. To make the theory positive-definite, some modification is required so as to preserve diffeomorphism invariance due to the Faddeev-Popov ghosts with a negative central charge.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2020)127
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  DOI ID：10.1007/JHEP04(2020)127, ISSN：1126-6708, eISSN：1029-8479, SCOPUS ID：85084132849
• Gravitational perturbations as TT¯-deformations in 2D dilaton gravity systems　　　　　　　　　　　　　　　
  Takaaki Ishii; Suguru Okumura; Jun ichi Sakamoto; Kentaroh Yoshida
  Nuclear Physics B, 巻：951, 2020年02月, ［査読有り］
  We consider gravitational perturbations of 2D dilaton gravity systems and show that these can be recast into TT¯-deformations (at least) under certain conditions, where T means the energy-momentum tensor of the matter field coupled to a dilaton gravity. In particular, the class of theories under this condition includes a Jackiw-Teitelboim (JT) theory with a negative cosmological constant including conformal matter fields. This is a generalization of the preceding work on the flat-space JT gravity by S. Dubovsky, V. Gorbenko and M. Mirbabayi [arXiv:1706.06604].
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2019.114901
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  DOI ID：10.1016/j.nuclphysb.2019.114901, ISSN：0550-3213, SCOPUS ID：85077044978
• Nonrelativistic hybrid geometries with gravitational gauge-fixing terms　　　　　　　　　　　　　　　
  Sinya Aoki; Janos Balog; Shuichi Yokoyama; Kentaroh Yoshida
  Physical Review Research, 巻：2, 号：1, 2020年02月, ［査読有り］
  We search a gravitational system that allows a nonrelativistic hybrid geometry interpolating the Schrödinger and Lifshitz spacetimes as a solution. As such a candidate an Einstein-Maxwell-Higgs system naturally arises and we verify that this system indeed supports the hybrid geometry with the help of a gauge-fixing term for diffeomorphism. As a result, this gravitational system may be interpreted as a holographic dual of a general nonrelativistic system at the boundary.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevResearch.2.013169
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  DOI ID：10.1103/PhysRevResearch.2.013169, ISSN：2643-1564, SCOPUS ID：85094505098
• O(d,d) transformations preserve classical integrability　　　　　　　　　　　　　　　
  Domenico Orlando; Susanne Reffert; Yuta Sekiguchi; Kentaroh Yoshida
  Nuclear Physics B, 巻：950, 2020年01月, ［査読有り］
  In this note, we study the action of O(d,d) transformations on the integrable structure of two-dimensional non-linear sigma models via the doubled formalism. We construct the Lax pairs associated with the O(d,d)-transformed model and find that they are in general non-local because they depend on the winding modes. We conclude that every O(d,d;R) deformation preserves integrability. As an application we compute the Lax pairs for continuous families of deformations, such as JJ¯ marginal deformations and TsT transformations of the three-sphere with H-flux.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2019.114880
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  DOI ID：10.1016/j.nuclphysb.2019.114880, ISSN：0550-3213, SCOPUS ID：85075778933
• Recent Progress on Yang-Baxter Deformation and Generalized Supergravity　　　　　　　　　　　　　　　
  Kentaroh Yoshida
  Springer Proceedings in Mathematics and Statistics, 巻：335, 開始ページ：203, 終了ページ：218, 2020年, ［査読有り］
  In recent years, great progress has been made on a systematic method to perform an integrable deformation of a two-dimensional relativistic non-linear sigma model. The deformations are labeled by classical r-matrices satisfying the classical Yang-Baxter equation, and this method is called the Yang-Baxter deformation. It was generalized to type IIB superstring theory defined on the AdS background and gave rise to a lot of integrable backgrounds including well-known backgrounds such as the Lunin-Maldacena background, a gravity dual for a non-commutative gauge theory, and a Schrdinger spacetime. In addition, the study of Yang-Baxter deformation led to the discovery of a generalized type IIB supergravity. In this proceeding, I will give a short summary of the recent progress on the Yang-Baxter deformation and the generalized supergravity.
  研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1007/978-981-15-7775-8_13
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  DOI ID：10.1007/978-981-15-7775-8_13, ISSN：2194-1009, eISSN：2194-1017, SCOPUS ID：85094117514
• SUSY and the bi-vector　　　　　　　　　　　　　　　
  Orlando, Domenico; Susanne Reffert; Sekiguchi, Yuta; Kentaroh Yoshida
  Phys.Scripta, 巻：94, 号：9, 開始ページ：095001, 終了ページ：095001, 2019年06月, ［査読有り］
  In this note we give an explicit formula for the preserved Killing spinors in deformed string theory backgrounds corresponding to integrable Yang-Baxter deformations realized via (sequences of) TsT transformations. The Killing spinors can be expressed only in terms of the bi-vector Θ which encodes the deformation. This formula is applicable to deformed backgrounds related to r-matrices of various ranks, including those that do not satisfy the unimodularity condition and give rise to backgrounds in generalized supergravity. We conjecture that our formula also remains valid for integrable deformations which are not realized via TsT transformations and motivate this conjecture by explicit examples.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1402-4896/ab1ab9
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  DOI ID：10.1088/1402-4896/ab1ab9, ISSN：0031-8949, eISSN：1402-4896, ORCID：58516446, arXiv ID：arXiv:1811.11764, SCOPUS ID：85071198416
• Holographic geometry for nonrelativistic systems emerging from generalized flow equations　　　　　　　　　　　　　　　
  Sinya Aoki; Shuichi Yokoyama; Kentaroh Yoshida
  Physical Review D, 巻：99, 号：12, 2019年06月, ［査読有り］
  An intriguing result presented by two of the present authors is that an anti-de Sitter space can be derived from a conformal field theory by considering a flow equation. A natural expectation is that given a certain data on the boundary system, the associated geometry would be able to emerge from a flow, even beyond the conformal case. As a step along this line, we examine this scenario for nonrelativistic systems with anisotropic scaling symmetries, such as Lifshitz field theories and Schrödinger invariant theories. In consequence we obtain a new hybrid geometry of Lifshitz and Schrödinger spacetimes as a general holographic geometry in this framework. We confirm that this geometry reduces to each of them by considering special nonrelativistic models.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.99.126002
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  DOI ID：10.1103/PhysRevD.99.126002, ISSN：2470-0010, eISSN：2470-0029, SCOPUS ID：85067876953
• Weyl Invariance of String Theories in Generalized Supergravity Backgrounds　　　　　　　　　　　　　　　
  José J. Fernández-Melgarejo; Jun-Ichi Sakamoto; Yuho Sakatani; Kentaroh Yoshida
  Physical Review Letters, 巻：122, 号：11, 2019年03月, ［査読有り］
  We revisit Weyl invariance string theories in generalized supergravity backgrounds. A possible counterterm was constructed in a work by Sakamoto, Sakatani, and Yoshida, but it seems to be a point of controversy in some literatures whether or not it is nonlocal. To settle down this issue, we show that the counterterm may be local and exactly cancels out the one-loop trace anomaly in generalized supergravity backgrounds.
  American Physical Society, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevLett.122.111602
  DOI ID：10.1103/PhysRevLett.122.111602, ISSN：1079-7114, PubMed ID：30951328, SCOPUS ID：85063279383
• Killing spinors from classical $r$-matrices　　　　　　　　　　　　　　　
  Orlando, Domenico; Reffert, Susanne; Sekiguchi, Yuta; Kentaroh Yoshida
  J.Phys.A, 巻：51, 号：39, 開始ページ：395401, 終了ページ：395401, 2018年08月, ［査読有り］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8121/aad8c2
  DOI ID：10.1088/1751-8121/aad8c2, ORCID：48400309, arXiv ID：arXiv:1805.00948
• Weyl transformation and regular solutions in a deformed Jackiw–Teitelboim model　　　　　　　　　　　　　　　
  Okumura Suguru; Yoshida Kentaroh
  Nucl.Phys.B, 巻：933, 開始ページ：234, 終了ページ：247, 2018年08月, ［査読有り］
  We revisit a deformed Jackiw–Teitelboim model with a hyperbolic dilaton potential, constructed in the preceding work [arXiv:1701.06340]. Several solutions are discussed in a series of the subsequent papers, but all of them are pathological because of a naked singularity intrinsic to the deformation. In this paper, by employing a Weyl transformation to the original deformed model, we consider a Liouville-type potential with a cosmological constant term. Then regular solutions can be constructed with coupling to a conformal matter by using SL(2) transformations. For a black hole solution, the Bekenstein–Hawking entropy is computed from the area law. It can also be reproduced by evaluating the boundary stress tensor with an appropriate local counter-term (which is essentially provided by a Liouville-type potential).
  Elsevier B.V., 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2018.06.003
  DOI ID：10.1016/j.nuclphysb.2018.06.003, ISSN：0550-3213, ORCID：48400376, arXiv ID：arXiv:1801.10537, SCOPUS ID：85048742851
• Conformal twists, Yang–Baxter σ-models & holographic noncommutativity　　　　　　　　　　　　　　　
  Araujo Thiago; Bakhmatov Ilya; Colgáin Eoin Ó; Sakamoto Jun-ichi; Sheikh-Jabbari Mohammad M; Yoshida Kentaroh
  J.Phys.A, 巻：51, 号：23, 開始ページ：235401, 終了ページ：235401, 2018年05月, ［査読有り］
  Expanding upon earlier results (Araujo et al 2017 Phys. Rev. D 95 105006), we present a compendium of σ-models associated with integrable deformations of AdS5 generated by solutions to homogenous classical Yang-Baxter equation. Each example we study from four viewpoints: conformal (Drinfeld) twists, closed string gravity backgrounds, open string parameters and proposed dual noncommutative (NC) gauge theory. Irrespective of whether the deformed background is a solution to supergravity or generalized supergravity, we show that the open string metric associated with each gravity background is undeformed AdS5 with constant open string coupling and the NC structure Θ is directly related to the conformal twist. One novel feature is that Θ exhibits 'holographic noncommutativity': while it may exhibit non-trivial dependence on the holographic direction, its value everywhere in the bulk is uniquely determined by its value at the boundary, thus facilitating introduction of a dual NC gauge theory. We show that the divergence of the NC structure Θ is directly related to the unimodularity of the twist. We discuss the implementation of an outer automorphism of the conformal algebra as a coordinate transformation in the AdS bulk and discuss its implications for Yang-Baxter σ-models and self-T-duality based on fermionic T-duality. Finally, we comment on implications of our results for the integrability of associated open strings and planar integrability of dual NC gauge theories.
  Institute of Physics Publishing, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8121/aac195
  DOI ID：10.1088/1751-8121/aac195, ISSN：1751-8121, ORCID：48400320, arXiv ID：arXiv:1705.02063, SCOPUS ID：85047733490
• T-folds from Yang-Baxter deformations　　　　　　　　　　　　　　　
  Jose J. Fernandez-Melgarejo; Jun-ice Sakamoto; Yuko Sakatani; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：12, 号：12, 開始ページ：108, 終了ページ：108, 2017年12月, ［査読有り］
  Yang-Baxter (YB) deformations of type IIB string theory have been well studied from the viewpoint of classical integrability. Most of the works, however, are focused upon the local structure of the deformed geometries and the global structure still remains unclear. In this work, we reveal a non-geometric aspect of YB-deformed backgrounds as T-fold by explicitly showing the associated O(D, D; Z) T-duality monodromy. In particular, the appearance of an extra vector field in the generalized supergravity equations (GSE) leads to the non-geometric Q-flux. In addition, we study a particular solution of GSE that is obtained by a non-Abelian T-duality but cannot be expressed as a homogeneous YB deformation, and show that it can also be regarded as a T-fold. This result indicates that solutions of GSE should be non-geometric quite in general beyond the YB deformation.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP12(2017)108
  DOI ID：10.1007/JHEP12(2017)108, ISSN：1029-8479, ORCID：48400282, arXiv ID：arXiv:1710.06849, Web of Science ID：WOS:000418374200009
• I in generalized supergravity　　　　　　　　　　　　　　　
  T. Araujo; E. O. Colgain; J. Sakamoto; M. M. Sheikh-Jabbari; K. Yoshida
  EUROPEAN PHYSICAL JOURNAL C, 巻：77, 号：11, 開始ページ：739, 終了ページ：739, 2017年11月, ［査読有り］
  We showed in previous work that for homogeneous Yang-Baxter (YB) deformations of AdS(5)xS(5) the open string metric and coupling and as a result the closed string density e-2 Phi root g remain undeformed. In this work, in addition to extending these results to the deformation associated with the modified CYBE or eta-deformation, we identify the Page forms as the open string counterpart for RR fields and demonstrate case by case that the non-zero Page forms remain invariant under YB deformations. We give a physical meaning to the Killing vector I of generalized supergravity and show for all YB deformations: (1) I appears as a current for the center of mass motion on the worldvolume of a D-brane probing the background, (2) I is equal to the divergence of the noncommutativity parameter, (3) I exhibits "holographic" behavior where the radial component of I vanishes at the AdS boundary and (4) in pure spinor formalism I is related to a certain state in the BRST cohomology.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1140/epjc/s10052-017-5316-5
  DOI ID：10.1140/epjc/s10052-017-5316-5, ISSN：1434-6044, eISSN：1434-6052, ORCID：48400374, arXiv ID：arXiv:1708.03163, Web of Science ID：WOS:000414450100001
• Comments on 2D dilaton gravity system with a hyperbolic dilaton potential　　　　　　　　　　　　　　　
  Hideki Kyono; Suguru Okumura; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：923, 開始ページ：126, 終了ページ：143, 2017年10月, ［査読有り］
  We proceed to study a (1 + 1)-dimensional dilaton gravity system with a hyperbolic dilaton potential. Introducing a couple of new variables leads to two copies of Liouville equations with two constraint conditions. In particular, in conformal gauge, the constraints can be expressed with Schwarzian derivatives. We revisit the vacuum solutions in light of the new variables and reveal its dipole-like structure. Then we present a time-dependent solution which describes formation of a black hole with a pulse. Finally, the black hole thermodynamics is considered by taking account of conformal matters from two points of view: 1) the Bekenstein-Hawking entropy and 2) the boundary stress tensor. The former result agrees with the latter one with a certain counter-term. (C) 2017 The Authors. Published by Elsevier B.V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2017.07.013
  DOI ID：10.1016/j.nuclphysb.2017.07.013, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400372, arXiv ID：arXiv:1704.07410, Web of Science ID：WOS:000413405200006
• Homogeneous Yang-Baxter deformations as generalized diffeomorphisms　　　　　　　　　　　　　　　
  Jun-ichi Sakamoto; Yuho Sakatani; Kentaroh Yoshida
  JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 巻：50, 号：41, 開始ページ：415401, 終了ページ：415401, 2017年10月, ［査読有り］
  Yang-Baxter (YB) deformations of string sigma model provide deformed target spaces. We propose that homogeneous YB deformations always lead to a certain class of beta-twisted backgrounds and represent the bosonic part of the supergravity fields in terms of the classical r-matrix associated with the YB deformation. We then show that various beta-twisted backgrounds can be realized by considering generalized diffeomorphisms in the undeformed background. Our result extends the notable relation between the YB deformations and (non-commuting) TsT transformations. We also discuss more general deformations beyond the YB deformations.
  IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8121/aa8896
  DOI ID：10.1088/1751-8121/aa8896, ISSN：1751-8113, eISSN：1751-8121, ORCID：48400346, arXiv ID：arXiv:1705.07116, Web of Science ID：WOS:000410831700001
• Yang Baxter deformations of W-2,W-4 x T-1,T-1 and the associated T-dual models　　　　　　　　　　　　　　　
  Jun-ichi Sakamoto; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：921, 開始ページ：805, 終了ページ：828, 2017年08月, ［査読有り］
  Recently, for principal chiral models and symmetric coset sigma models, Hoare and Tseytlin proposed an interesting conjecture that the Yang Baxter deformations with the homogeneous classical Yang-Baxter equation are equivalent to non-abelian T-dualities with topological terms. It is significant to examine this conjecture for non-symmetric (i.e., non-integrable) cases. Such an example is the W-2,W-4 x T-1,T-1 background. In this note, we study Yang-Baxter deformations of type IIB string theory defined on W-2,W-4 x T-1,T-1 and the associated T-dual models, and show that this conjecture is valid even for this case. Our result indicates that the conjecture would be valid beyond integrability. (C) 2017 The Authors. Published by Elsevier B.V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2017.06.017
  DOI ID：10.1016/j.nuclphysb.2017.06.017, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400370, arXiv ID：arXiv:1612.08615, Web of Science ID：WOS:000408301200033
• Weyl invariance for generalized supergravity backgrounds from the doubled formalism　　　　　　　　　　　　　　　
  Jun-ichi Sakamoto; Yuho Sakatani; Kentaroh Yoshida
  PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 巻：2017, 号：5, 開始ページ：053B07, 2017年05月, ［査読有り］
  It has recently been shown that a set of the generalized type IIB supergravity equations follows from the requirement of kappa symmetry of the type IIB Green-Schwarz superstring theory defined on an arbitrary background. In this paper, we show that the whole bosonic part of the generalized type II supergravity equations can be reproduced from the T-duality covariant equations of motion of the double field theory by choosing a non-standard solution of the strong constraint. Then, by using the doubled formalism, we show the Weyl invariance of the bosonic string sigma model on a generalized gravity background. According to the dual-coordinate dependence of the dilaton, the Fradkin-Tseytlin term nicely removes the Weyl anomaly. This result seems likely to support that string theories can be consistently defined on arbitrary generalized supergravity backgrounds.
  OXFORD UNIV PRESS INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/ptep/ptx067
  DOI ID：10.1093/ptep/ptx067, ISSN：2050-3911, ORCID：48400357, arXiv ID：arXiv:1703.09213, Web of Science ID：WOS:000405373100012
• Yang-Baxter sigma-models, conformal twists, and noncommutative Yang-Mills theory　　　　　　　　　　　　　　　
  T. Araujo; I. Bakhmatov; E. O. Colgain; J. Sakamoto; M. M. Sheikh-Jabbari; K. Yoshida
  PHYSICAL REVIEW D, 巻：95, 号：10, 開始ページ：105006, 終了ページ：105006, 2017年05月, ［査読有り］
  The Yang-Baxter s-model is a systematic way to generate integrable deformations of AdS(5) x S-5. We recast the deformations as seen by open strings, where the metric is undeformed AdS(5) x S-5 with constant string coupling, and all information about the deformation is encoded in the noncommutative (NC) parameter Theta. We identify the deformations of AdS(5) as twists of the conformal algebra, thus explaining the noncommutativity. We show that the unimodularity condition on gamma-matrices for supergravity solutions translates into Theta being divergence-free. Integrability of the s-model for unimodular sigma-matrices implies the existence and planar integrability of the dual NC gauge theory.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.95.105006
  DOI ID：10.1103/PhysRevD.95.105006, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400307, arXiv ID：arXiv:1702.02861, Web of Science ID：WOS:000402053200005
• Generalized gravity from modified DFT　　　　　　　　　　　　　　　
  Yuho Sakatani; Shozo Uehara; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：123, 終了ページ：123, 2017年04月, ［査読有り］
  Recently, generalized equations of type IIB supergravity have been derived from the requirement of classical kappa-symmetry of type IIB superstring theory in the Green-Schwarz formulation. These equations are covariant under generalized T-duality transformations and hence one may expect a formulation similar to double field theory (DFT). In this paper, we consider a modification of the DFT equations of motion by relaxing a condition for the generalized covariant derivative with an extra generalized vector. In this modified double field theory (mDFT), we show that the flatness condition of the modified generalized Ricci tensor leads to the NS-NS part of the generalized equations of type IIB supergravity. In particular, the extra vector fields appearing in the generalized equations correspond to the extra generalized vector in mDFT. We also discuss duality symmetries and a modification of the string charge in mDFT.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2017)123
  DOI ID：10.1007/JHEP04(2017)123, ISSN：1029-8479, ORCID：48400283, arXiv ID：arXiv:1611.05856, Web of Science ID：WOS:000402860800006
• Fate of chaotic strings in a confining geometry　　　　　　　　　　　　　　　
  Takaaki Ishii; Keiju Murata; Kentaroh Yoshida
  PHYSICAL REVIEW D, 巻：95, 号：6, 開始ページ：066019, 終了ページ：066019, 2017年03月, ［査読有り］
  We study chaos and turbulence on classical closed strings in nonintegrable string theory. The string motion is considered in the five-dimensional anti-de Sitter (AdS) soliton spacetime taken as the target space. We first revisit classical chaos using a cohomogeneity-1 string ansatz. We then turn to turbulent behaviors of the classical strings when the spatial dependence of the string world sheet is included. Sensitivity to initial conditions in chaotic systems suggests that the string under chaos tends to stretch in the AdS soliton spacetime in a Lyapunov time scale. In this process, the orbital angular momentum transfers to internal spin due to the turbulence on the string. It follows that the string stays around the tip of the AdS soliton with a jumbled profile. We evaluate the spectra of conserved quantities and discuss their universal power-law scalings in the turbulent behaviors.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.95.066019
  DOI ID：10.1103/PhysRevD.95.066019, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400390, arXiv ID：arXiv:1610.05833, Web of Science ID：WOS:000399147100016
• Deformations of the Almheiri-Polchinski model　　　　　　　　　　　　　　　
  Hideki Kyono; Suguru Okumura; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：03, 号：3, 開始ページ：173, 終了ページ：173, 2017年03月, ［査読有り］
  We study deformations of the Almheiri-Polchinski (AP) model by employing the Yang-Baxter deformation technique. The general deformed AdS 2 metric becomes a solution of a deformed AP model. In particular, the dilaton potential is deformed from a simple quadratic form to a hyperbolic function-type potential similarly to integrable deformations. A specific solution is a deformed black hole solution. Because the deformation makes the spacetime structure around the boundary change drastically and a new naked singularity appears, the holographic interpretation is far from trivial. The Hawking temperature is the same as the undeformed case but the Bekenstein-Hawking entropy is modi fied due to the deformation. This entropy can also be reproduced by evaluating the renormalized stress tensor with an appropriate counter-term on the regularized screen close to the singularity.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP03(2017)173
  DOI ID：10.1007/JHEP03(2017)173, ISSN：1029-8479, ORCID：48400284, arXiv ID：arXiv:1701.06340, Web of Science ID：WOS:000397972600005
• Generalized type IIB supergravity equations and non-Abelian classical r-matrices　　　　　　　　　　　　　　　
  Domenico Orlando; Susanne Reffert; Jun-ichi Sakamoto; Kentaroh Yoshida
  JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 巻：49, 号：44, 開始ページ：445403, 終了ページ：445403, 2016年11月, ［査読有り］
  We study Yang-Baxter deformations of the AdS(5) x S-5 superstring with non-Abelian classical r-matrices which satisfy the homogeneous classical Yang-Baxter equation. By performing a supercoset construction, we can get deformed AdS(5) x S-5 backgrounds. While this is a new area of research, the current understanding is that Abelian classical r-matrices give rise to solutions of type IIB supergravity, while non-Abelian classical r-matrices lead to solutions of the generalized supergravity equations. We examine here some examples of non-Abelian classical r-matrices and derive the associated backgrounds explicitly. All of the resulting backgrounds satisfy the generalized equations. For some of them, we derive 'T-dualized' backgrounds by adding a linear coordinate dependence to the dilaton and show that these satisfy the usual type IIB supergravity equations. Remarkably, some of the 'T-dualized' backgrounds are locally identical to undeformed AdS(5) x S-5 after an appropriate coordinate transformation, but this seems not to be generally the case.
  IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8113/49/44/445403
  DOI ID：10.1088/1751-8113/49/44/445403, ISSN：1751-8113, eISSN：1751-8121, ORCID：48400338, arXiv ID：arXiv:1607.00795, Web of Science ID：WOS:000385277100015
• Melnikov's method in String Theory　　　　　　　　　　　　　　　
  Yuhma Asano; Hideki Kyono; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：09, 号：9, 開始ページ：103, 終了ページ：103, 2016年09月, ［査読有り］
  Melnikov's method is an analytical way to show the existence of classical chaos generated by a Smale horseshoe. It is a powerful technique, though its applicability is somewhat limited. In this paper, we present a solution of type IIB supergravity to which Melnikov's method is applicable. This is a brane-wave type deformation of the AdS(5)xS(5) background. By employing two reduction ansatze, we study two types of coupled pendulum-oscillator systems. Then the Melnikov function is computed for each of the systems by following the standard way of Holmes and Marsden and the existence of chaos is shown analytically.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP09(2016)103
  DOI ID：10.1007/JHEP09(2016)103, ISSN：1029-8479, ORCID：48400356, arXiv ID：arXiv:1607.07302, Web of Science ID：WOS:000383721900012
• Supercoset construction of Yang-Baxter-deformed AdS(5)xS(5) backgrounds　　　　　　　　　　　　　　　
  Hideki Kyono; Kentaroh Yoshida
  PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 巻：2016, 号：8, 開始ページ：083B03, 2016年08月, ［査読有り］
  We study Yang-Baxter deformations of the AdS(5)xS(5) superstring with the classical Yang-Baxter equation. We make a general argument on the supercoset construction and present a formula to describe the dilaton in terms of classical r-matrices. The supercoset construction is explicitly performed for some classical r-matrices, and the full backgrounds including the Ramond-Ramond (R-R) sector and dilaton are derived. Within the class of Abelian r-matrices, perfect agreement is shown for well-known examples including gravity duals of non-commutative gauge theories, gamma-deformations of S-5 and Schrodinger spacetimes. It is remarkable that the supercoset construction works well, even if the resulting backgrounds are not maximally supersymmetric. In particular, three-parameter gamma-deformations of S-5 and Schrodinger spacetimes do not preserve any supersymmetries. As for non-Abelian r-matrices, we will focus upon a specific example. The resulting background does not satisfy the equation of motion of the Neveu-Schwarz-Neveu-Schwarz two-form because the R-R three-form is not closed.
  OXFORD UNIV PRESS INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/ptep/ptw111
  DOI ID：10.1093/ptep/ptw111, ISSN：2050-3911, ORCID：48400305, arXiv ID：arXiv:1605.02519, Web of Science ID：WOS:000386893200008
• Generalized quark-antiquark potentials from a q-deformed AdS(5) x S-5 background　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS, 巻：2016, 号：6, 開始ページ：063B01, 2016年06月, ［査読有り］
  We study minimal surfaces with a single cusp in a q-deformed AdS(5) x S-5 background. The cusp is composed of two half-lines with an arbitrary angle and is realized on a surface specified in the deformed AdS5. The classical string solutions attached to this cusp are regarded as a generalization of configurations studied by Drukker and Forini [J. High Energy Phys. 1106, 131 (2011) [arXiv: 1105.5144 [hep-th]]] in the undeformed case. By taking an antiparallel-lines limit, a quark-antiquark potential for the q-deformed case is derived with a certain subtraction scheme. The resulting potential becomes linear at short distances with a finite deformation parameter. In particular, the linear behavior for the gravity dual of noncommutative gauge theories can be reproduced as a special scaling limit. Finally we study the near straight-line limit of the potential.
  OXFORD UNIV PRESS INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1093/ptep/ptw059
  DOI ID：10.1093/ptep/ptw059, ISSN：2050-3911, ORCID：48400281, arXiv ID：arXiv:1602.06786, Web of Science ID：WOS:000381227000007
• Chaos in chiral condensates in gauge theories　　　　　　　　　　　　　　　
  Koji Hashimoto; Keiju Murata; Kentaroh Yoshida
  Phys.Rev.Lett., 巻：117, 号：23, 開始ページ：231602, 終了ページ：231602, 2016年05月, ［査読有り］
  Assigning a chaos index for dynamics of generic quantum field theories is a
  challenging problem, because the notion of Lyapunov exponent, which is useful
  for singling out chaotic behaviors, works only in classical systems. We address
  the issue by using the AdS/CFT correspondence, as the large $N_c$ limit
  provides a classicalization (other than the standard $\hbar \to 0$) while
  keeping nontrivial quantum condensation. We demonstrate the chaos in the
  dynamics of quantum gauge theories: Time evolution of homogeneous quark
  condensates $\langle \bar{q}q\rangle$ and $\langle \bar{q} \gamma_5 q\rangle$
  in an ${\cal N}=2$ supersymmetric QCD with the $SU(N_c)$ gauge group at large
  $N_c$ and at large 't Hooft coupling $\lambda \equiv N_c g_{\rm YM}^2$ exhibits
  a positive Lyapunov exponent. The chaos dominates the phase space for energy
  density $E \gtrsim (6\times 10^2)\times m_q^4(N_c/\lambda^2) $ where $m_q$ is
  the quark mass. We evaluate the largest Lyapunov exponent as a function of
  $(N_c,\lambda,E)$ and find that the ${\cal N}=2$ supersymmetric QCD is more
  chaotic for smaller $N_c$.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevLett.117.231602
  DOI ID：10.1103/PhysRevLett.117.231602, ORCID：48400294, arXiv ID：arXiv:1605.08124
• Yang-Baxter sigma models and Lax pairs arising from $\kappa$-Poincaré $r$-matrices　　　　　　　　　　　　　　　
  Borowiec Andrzej; Kyono Hideki; Lukierski Jerzy; Sakamoto Jun-ichi; Yoshida Kentaroh
  JHEP, 巻：04, 号：4, 開始ページ：079, 2016年04月, ［査読有り］
  We study Yang-Baxter sigma models with deformed 4d Minkowski spacetimes arising from classical r-matrices associated with kappa-deformations of the Poincare algebra. These classical kappa-Poincare r-matrices describe three kinds of deformations: 1) the standard deformation, 2) the tachyonic deformation, and 3) the light-cone deformation. For each deformation, the metric and two-form B-field are computed from the associated r-matrix. The first two deformations, related to the modified classical Yang-Baxter equation, lead to T-duals of dS(4) and AdS(4), respectively. The third deformation, associated with the homogeneous classical Yang-Baxter equation, leads to a time-dependent pp-wave background. Finally, we construct a Lax pair for the generalized kappa-Poincare r-matrix that unifies the three kinds of deformations mentioned above as special cases.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2016)079
  DOI ID：10.1007/JHEP04(2016)079, ISSN：1029-8479, ORCID：48400315, arXiv ID：arXiv:1510.03083, Web of Science ID：WOS:000375332600006
• Yang–Baxter invariance of the Nappi–Witten model　　　　　　　　　　　　　　　
  Kyono Hideki; Yoshida Kentaroh
  Nucl.Phys.B, 巻：905, 開始ページ：242, 終了ページ：250, 2016年04月, ［査読有り］
  We study Yang-Baxter deformations of the Nappi-Witten model with a prescription invented by Delduc, Magro and Vicedo. The deformations are specified by skew-symmetric classical r-matrices satisfying (modified) classical Yang-Baxter equations. We show that the sigma-model metric is invariant under arbitrary deformations (while the coefficient of B-field is changed) by utilizing the most general classical r-matrix. Furthermore, the coefficient of B-field is determined to be the original value from the requirement that the one-loop beta-function should vanish. After all, the Nappi-Witten model is the unique conformal theory within the class of the Yang-Baxter deformations preserving the conformal invariance. (C) 2016 The Authors. Published by Elsevier B.V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2016.02.017
  DOI ID：10.1016/j.nuclphysb.2016.02.017, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400300, arXiv ID：arXiv:1511.00404, Web of Science ID：WOS:000373571400010
• Towards the gravity/CYBE correspondence $— the$ $current$ $status —$　　　　　　　　　　　　　　　
  Matsumoto Takuya; Yoshida Kentaroh
  J.Phys.Conf.Ser., 巻：670, 号：1, 開始ページ：012033, 2016年, ［査読有り］
  We give a brief summary of Yang-Baxter deformations of the AdS(5) xS(5) superstring by focusing upon four examples, 1) gravity duals for noncommutative gauge theories, 2) gamma-deformations of S-5, 3) Schrodinger spacetimes and 4) abelian twists of the global AdS(5).
  IOP PUBLISHING LTD, 英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1088/1742-6596/670/1/012033
  DOI ID：10.1088/1742-6596/670/1/012033, ISSN：1742-6588, ORCID：48400396, Web of Science ID：WOS:000382083700033
• Towards the gravity/CYBE correspondence beyond integrability - Yang-Baxter deformations of T-1,T-1 -　　　　　　　　　　　　　　　
  P. Marcos Crichigno; Takuya Matsumoto; Kentaroh Yoshida
  XXIII INTERNATIONAL CONFERENCE ON INTEGRABLE SYSTEMS AND QUANTUM SYMMETRIES (ISQS-23), 巻：670, 号：1, 開始ページ：012019, 2016年, ［査読有り］
  Yang-Baxter sigma models, proposed by Klimcik and Delduc-Magro-Vicedo, have been recognized as a powerful framework for studying integrable deformations of two-dimensional non-linear sigma models. In this short article, as an important generalization, we review a non-integrable sigma model in the Yang-Baxter sigma model approach based on [arXiv:1406.2249]. In particular, we discuss a family of deformations of the 5D Sasaki-Einstein manifold T-1,T-1, instead of the standard deformations of the 5-sphere S-5. For this purpose, we first describe a novel construction of T-1,T-1 as a supercoset, and provide a physical interpretation of this construction from viewpoint of the dual Klebanov-Witten field theory. Secondly, we consider a 3-parameter deformation of T-1,T-1 by using classical r-matrices satisfying the classical Yang-Baxter equation (CYBE). The resulting metric and NS-NS two-form completely agree with the ones previously obtained via TsT (T-dual - shift - T-dual) transformations, and contain the Lunin-Maldacena background as a special case. Our result indicates that what we refer to as the gravity/CYBE(Classical Yang-Baxter Equation) correspondence can be extended beyond integrable cosets.
  IOP PUBLISHING LTD, 英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1088/1742-6596/670/1/012019
  DOI ID：10.1088/1742-6596/670/1/012019, ISSN：1742-6588, ORCID：48400325, arXiv ID：arXiv:1510.00835, Web of Science ID：WOS:000382083700019
• Lax pairs for deformed Minkowski spacetimes　　　　　　　　　　　　　　　
  Hideki Kyono; Jun-ichi Sakamoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：01, 号：1, 開始ページ：143, 2016年01月, ［査読有り］
  We proceed to study Yang-Baxter deformations of 4D Minkowski spacetime based on a conformal embedding. We first revisit a Melvin background and argue a Lax pair by adopting a simple replacement law invented in 1509.00173. This argument enables us to deduce a general expression of Lax pair. Then the anticipated Lax pair is shown to work for arbitrary classical r-matrices with Poincare generators. As other examples, we present Lax pairs for pp-wave backgrounds, the Hashimoto-Sethi background, the Spradlin-Takayanagi-Volovich background.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP01(2016)143
  DOI ID：10.1007/JHEP01(2016)143, ISSN：1029-8479, ORCID：48400286, arXiv ID：arXiv:1512.00208, Web of Science ID：WOS:000370440000001
• Lax pairs on Yang-Baxter deformed backgrounds　　　　　　　　　　　　　　　
  Takashi Kameyama; Hideki Kyono; Jun-ichi Sakamoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：11, 号：11, 開始ページ：043, 2015年11月, ［査読有り］
  We explicitly derive Lax pairs for string theories on Yang-Baxter deformed backgrounds, 1) gravity duals for noncommutative gauge theories, 2) gamma-deformations of S-5, 3) Schrodinger spacetimes and 4) abelian twists of the global AdS(5). Then we can find out a concise derivation of Lax pairs based on simple replacement rules. Furthermore, each of the above deformations can be reinterpreted as twisted boundary conditions with the undeformed background by using the rules. As another derivation, the Lax pair for gravity duals for noncommutative gauge theories is reproduced from the one for a q-deformed AdS(5)xS(5) by taking a scaling limit.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP11(2015)043
  DOI ID：10.1007/JHEP11(2015)043, ISSN：1029-8479, ORCID：48400404, arXiv ID：arXiv:1509.00173, Web of Science ID：WOS:000365007000004
• Yang-Baxter deformations of Minkowski spacetime　　　　　　　　　　　　　　　
  Takuya Matsumoto; Domenico Orlando; Susanne Reffert; Jun-ichi Sakamoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：10, 号：10, 開始ページ：185, 2015年10月, ［査読有り］
  We study Yang-Baxter deformations of 4D Minkowski spacetime. The Yang-Baxter sigma model description was originally developed for principal chiral models based on a modified classical Yang-Baxter equation. It has been extended to coset curved spaces and models based on the usual classical Yang-Baxter equation. On the other hand, for flat space, there is the obvious problem that the standard bilinear form degenerates if we employ the familiar coset Poincare group/Lorentz group. Instead we consider a slice of AdS(5) by embedding the 4D Poincare group into the 4D conformal group SO(2,4). With this procedure we obtain metrics and B-fields as Yang-Baxter deformations which correspond to well-known configurations such as T-duals of Melvin backgrounds, Hashimoto-Sethi and Spradlin-Takayanagi-Volovich backgrounds, the T-dual of Grant space, pp-waves, and T-duals of dS(4) and AdS(4). Finally we consider a deformation with a classical r-matrix of Drinfeld-Jimbo type and explicitly derive the associated metric and B-field which we conjecture to correspond to a new integrable system.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP10(2015)185
  DOI ID：10.1007/JHEP10(2015)185, ISSN：1029-8479, ORCID：48400367, arXiv ID：arXiv:1505.04553, Web of Science ID：WOS:000364025600005
• Chaotic strings in a near Penrose limit of AdS(5) x T-1,T-1　　　　　　　　　　　　　　　
  Yuhma Asano; Daisuke Kawai; Hideki Kyono; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：08, 号：8, 開始ページ：060, 2015年08月, ［査読有り］
  We study chaotic motions of a classical string in a near Penrose limit of AdS(5) x T-1,T-1. It is known that chaotic solutions appear on R x T-1,T-1, depending on initial conditions. It may be interesting to ask whether the chaos persists even in Penrose limits or not. In this paper, we show that sub-leading corrections in a Penrose limit provide an unstable separatrix, so that chaotic motions are generated as a consequence of collapsed Kolmogorov-Arnold-Moser (KAM) tori. Our analysis is based on deriving a reduced system composed of two degrees of freedom by supposing a winding string ansatz. Then, we provide support for the existence of chaos by computing Poincare sections. In comparison to the AdS(5) x T-1,T-1 case, we argue that no chaos lives in a near Penrose limit of AdS(5) x S-5, as expected from the classical integrability of the parent system.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP08(2015)060
  DOI ID：10.1007/JHEP08(2015)060, ISSN：1029-8479, ORCID：48400345, arXiv ID：arXiv:1505.07583, SCOPUS ID：84939137265, Web of Science ID：WOS:000363519700007
• Minimal surfaces in q-deformed AdS(5) x S-5 with Poincare coordinates　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 巻：48, 号：24, 開始ページ：245401, 2015年06月, ［査読有り］
  We study minimal surfaces in q-deformed AdS(5) x S-5 with a new coordinate system introduced in the previous work (Kameyama and Yoshida 2015 J. Phys. A: Math. Theor. 48 075401). In this paper, we introduce Poincare coordinates for the deformed theory. We then construct minimal surfaces whose boundary shape is a circle. The solution corresponds to a 1/2 BPS circular Wilson loop in the q -> 1 limit. A remarkable point is that the classical Euclidean action is not divergent, unlike the original. This finiteness indicates that the q-deformation may be regarded as a UV regularization.
  IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8113/48/24/245401
  DOI ID：10.1088/1751-8113/48/24/245401, ISSN：1751-8113, eISSN：1751-8121, ORCID：48400355, arXiv ID：arXiv:1410.5544, Web of Science ID：WOS:000355253100011
• Chaos in the BMN matrix model　　　　　　　　　　　　　　　
  Yuhma Asano; Daisuke Kawai; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：191, 2015年06月, ［査読有り］
  We study classical chaotic motions in the Berenstein-Maldacena-Nastase (BMN) matrix model. For this purpose, it is convenient to focus upon a reduced system composed of two-coupled anharmonic oscillators by supposing an ansatz. We examine three ansatze: 1) two pulsating fuzzy spheres, 2) a single Coulomb-type potential, and 3) integrable fuzzy spheres. For the first two cases, we show the existence of chaos by computing Poincare sections and a Lyapunov spectrum. The third case leads to an integrable system. As a result, the BMN matrix model is not integrable in the sense of Liouville, though there may be some integrable subsectors.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2015)191
  DOI ID：10.1007/JHEP06(2015)191, ISSN：1029-8479, ORCID：48400280, arXiv ID：arXiv:1503.04594, Web of Science ID：WOS:000358317800001
• Schrödinger geometries arising from Yang-Baxter deformations　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2015, 号：4, 2015年04月, ［査読有り］
  Springer Science and Business Media LLC, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/jhep04(2015)180
  DOI ID：10.1007/jhep04(2015)180, ISSN：1029-8479, eISSN：1029-8479, ORCID：48400344, arXiv ID：arXiv:1502.00740, Web of Science ID：WOS:000353884400001
• Yang–Baxter sigma models based on the CYBE　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  Nuclear Physics B, 巻：893, 開始ページ：287, 終了ページ：304, 2015年04月, ［査読有り］
  Elsevier BV, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2015.02.009
  DOI ID：10.1016/j.nuclphysb.2015.02.009, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400397, arXiv ID：arXiv:1501.03665, Web of Science ID：WOS:000352045000012
• A holographic description of the Schwinger effect in a confining gauge theory　　　　　　　　　　　　　　　
  Daisuke Kawai; Yoshiki Sato; Kentaroh Yoshida
  INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 巻：30, 号：11, 開始ページ：1530026, 2015年04月, ［査読有り］, ［招待有り］
  This is a review of the recent progress on a holographic description of the Schwinger effect. In 2011, Semenoff and Zarembo proposed a scenario to study the Schwinger effect in the context of the AdS/CFT correspondence. The production rate of quark-antiquark pairs was computed in the Coulomb phase. In particular, it provided the critical value of external electric field, above which particles are freely created and the vacuum decays catastrophically. Then the potential analysis in the holographic approach was invented and it enabled us to study the Schwinger effect in the confining phase as well. A remarkable feature of the Schwinger effect in the confining phase is to exhibit another kind of the critical value, below which the pair production cannot occur and the vacuum of the system is nonperturbatively stable. The critical value is tantamount to the confining string tension. We computed the pair production rate numerically and introduced new exponents associated with the critical electric fields.
  WORLD SCIENTIFIC PUBL CO PTE LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1142/S0217751X15300264
  DOI ID：10.1142/S0217751X15300264, ISSN：0217-751X, eISSN：1793-656X, ORCID：48400308, arXiv ID：arXiv:1504.00459, Web of Science ID：WOS:000352992800001
• Yang-Baxter deformations and string dualities　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：03, 号：3, 開始ページ：137, 2015年03月, ［査読有り］
  We further study in intgrable deformations of the AdS(5) x S-5 superstring by following the Yang-Baxter sigma model approach with classical r-matrices satisfying the classical Yang-Baxter equation (CYBE). Deformed string backgrounds specified by r-matrices are considered as solutions of type LIB supergravity, and therefore the relation between gravitational solutions and r-matrices may be called the gravity/CYBE correspondence. In this paper, we present a family of string backgrounds associated with a classical r-matrices carrying two parameters and its three-parameter generalization. The two-parameter case leads to the metric and NS-NS two-form of a solution found by flubeny-Rangamani-Ross [hep-th/0504034] and another solution in [arXiv:11402.6147]. For all of the backgrounds associated with the three-parameter case, the metric and NS-NS two-form are reproduced by performing TsT transformations and 5-dualities for the undeformed AdS(5) x S-5 background. As a result, one can anticipate the R-R sector that should be reproduced via a supercoset construction.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP03(2015)137
  DOI ID：10.1007/JHEP03(2015)137, ISSN：1029-8479, ORCID：48400298, arXiv ID：arXiv:1412.3658, Web of Science ID：WOS:000351751000004
• A new coordinate system for q-deformed AdS(5) x S-5 and classical string solutions　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 巻：48, 号：7, 開始ページ：075401, 2015年02月, ［査読有り］
  We study a Gubser-Klebanov-Polyakov-like classical string solution on a q-deformed AdS(5) x S-5 background and argue the spacetime structure by using it as a probe. The solution cannot stretch beyond the singularity surface and this result may suggest that the holographic relation is realized inside the singularity surface. This observation leads us to introduce a new coordinate system which describes the spacetime only inside the singularity surface. With the new coordinate system, we study minimal surfaces and derive a deformed Neumann-Rosochatius system with a rigid string ansatz.
  IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8113/48/7/075401
  DOI ID：10.1088/1751-8113/48/7/075401, ISSN：1751-8113, eISSN：1751-8121, ORCID：48400401, arXiv ID：arXiv:1408.2189, Web of Science ID：WOS:000348437000014
• Deformations of T-1,T-1 as Yang-Baxter sigma models　　　　　　　　　　　　　　　
  P. Marcos Crichigno; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：12, 号：12, 開始ページ：085, 2014年12月, ［査読有り］
  We consider a family of deformations of T-1,T-1 in the Yang-Baxter sigma model approach. We first discuss a supercoset description of T-1,T-1, which makes manifest the full symmetry of the space and leads to the standard Sasaki-Einstein metric. Next, we consider three-parameter deformations of T-1,T-1 by using classical r-matrices satisfying the classical Yang-Baxter equation (CYBE). The resulting metric and NS-NS two-form agree exactly with the ones obtained via TsT transformations, and contain the Lunin-Maldacena background as a special case. It is worth noting that for AdS(5) x T-1,T-1, classical integrability for the full sector has been argued to be lost. Hence our result indicates that the Yang-Baxter sigma model approach is applicable even for non-integrable cosets. This observation suggests that the gravity/CYBE correspondence can be extended beyond integrable cases.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP12(2014)085
  DOI ID：10.1007/JHEP12(2014)085, ISSN：1029-8479, ORCID：48400350, arXiv ID：arXiv:1406.2249, Web of Science ID：WOS:000346244600001
• Probe brane dynamics on cosmological brane backgrounds　　　　　　　　　　　　　　　
  Kunihito Uzawa; Kentaroh Yoshida
  PHYSICS LETTERS B, 巻：738, 開始ページ：493, 終了ページ：498, 2014年11月, ［査読有り］
  We consider the dynamics of a single probe brane on various cosmological brane backgrounds. The on-shell condition of the static probe brane leads to the supersymmetric intersection rules for static BPS configurations, though the cosmological backgrounds do not preserve any supersymmetries. This is aremarkable feature associated with the cosmological backgrounds because in the static background the on-shell condition of the static brane gives no constraint on the brane configuration. Furthermore, it follows that under this condition there is no velocity-independent force for the probe brane even on the cosmological backgrounds. (C) 2014 The Authors. Published by Elsevier B. V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2014.10.030
  DOI ID：10.1016/j.physletb.2014.10.030, ISSN：0370-2693, eISSN：1873-2445, ORCID：48400407, arXiv ID：arXiv:1401.3664, Web of Science ID：WOS:000344624900074
• No pair production of open strings in a plane-wave background　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Hyeonjoon Shin; Kentaroh Yoshida
  PHYSICAL REVIEW D, 巻：90, 号：6, 開始ページ：066009, 2014年09月, ［査読有り］
  We consider whether an external electric field may cause the pair production of open strings in a type IIA plane-wave background. The boundary states of D-branes with condensates are constructed in the Green-Schwarz formulation of superstring theory with the light-cone gauge. The cylinder diagrams are computed with massive theta functions. Although the value of the electric field is bounded by the upper value, there is no pole in the amplitudes and it indicates that no pair production occurs in the plane-wave background. This result would be universal for a class of plane-wave backgrounds.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.90.066009
  DOI ID：10.1103/PhysRevD.90.066009, ISSN：1550-7998, eISSN：1550-2368, ORCID：48400319, arXiv ID：arXiv:1402.2048, Web of Science ID：WOS:000342128700005
• Anisotropic Landau-Lifshitz sigma models from q-deformed AdS(5)xS(5) superstrings　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：08, 号：8, 開始ページ：110, 2014年08月, ［査読有り］
  We consider bosonic subsectors of the q-deformed AdS(5)xS(5) superstring action and study the classical integrable structure of anisotropic Landau-Lifshitz sigma models (LLSMs) derived by taking fast-moving string limits. The subsectors are 1) deformed AdS(3) x S-1 and 2) R x deformed S-3. The cases 1) and 2) lead to a time-like warped SL(2) LLSM and a squashed S-3 LLSM, respectively. For each of them, we construct an infinite number of non-local conserved charges and show a quantum affine algebra at the classical level. Furthermore, a pp-wave like limit is applied for the case 1). The resulting system is a null-like warped SL(2) LLSM and exhibits a couple of Yangians through non-local gauge transformations associated with Jordanian twists.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP08(2014)110
  DOI ID：10.1007/JHEP08(2014)110, ISSN：1029-8479, ORCID：48400403, arXiv ID：arXiv:1405.4467, Web of Science ID：WOS:000341002100003
• Lunin-Maldacena backgrounds from the classical Yang-Baxter equation - towards the gravity/CYBE correspondence　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：135, 2014年06月, ［査読有り］
  We consider gamma-deformations of the AdS(5)xS(5) superstring as Yang-Baxter sigma models with classical r-matrices satisfying the classical Yang-Baxter equation (CYBE). An essential point is that the classical r-matrices are composed of Cartan generators only and then generate abelian twists. We present examples of the r-matrices that lead to real gamma-deformations of the AdS(5)xS(5) superstring. Finally we discuss a possible classification of integrable deformations and the corresponding gravity solution in terms of solutions of CYBE. This classification may be called the gravity/CYBE correspondence.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2014)135
  DOI ID：10.1007/JHEP06(2014)135, ISSN：1029-8479, ORCID：48400368, arXiv ID：arXiv:1404.1838, Web of Science ID：WOS:000338529400001
• SUSY properties of warped AdS(3)　　　　　　　　　　　　　　　
  Jaehoon Jeong; Eoin O. Colgain; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：036, 2014年06月, ［査読有り］
  We examine supersymmetric properties of null-warped AdS(3), or alternatively Schrodinger geometries, dual to putative warped CFTs in two dimensions. We classify super Schrodinger subalgebras of the superalgebra psu(1, 1|2). circle plus psu ( 1, 1|2), corresponding to the superconformal algebra of the AdS(3) x S-3 geometry. We comment on geometric realisations and provide a string theory description with enhanced supersymmetry in terms of intersecting D3-branes. For type IIB supergravity solutions based on T (1, 1), we consider the relationship between five-dimensional Schrodinger solutions and their three-dimensional null-warped counterparts, corresponding to R symmetry twists. Finally, we study a family of null-warped AdS(3) solutions in a setting where there is an ambiguity over the R symmetry and confirm that, for examples admitting a Kaluza-Klein (KK) reduction to three dimensions, the minimisation of a real superpotential of the three-dimensional gauged supergravity captures the central charge and R symmetry.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2014)036
  DOI ID：10.1007/JHEP06(2014)036, ISSN：1029-8479, ORCID：48400359, arXiv ID：arXiv:1402.3807, Web of Science ID：WOS:000337032000001
• Integrability of classical strings dual for noncommutative gauge theories　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：163, 2014年06月, ［査読有り］
  We derive the gravity duals of noncommutative gauge theories from the Yang-Baxter sigma model description of the AdS(5)xS(5) superstring with classical r-matrices. The corresponding classical r-matrices are 1) solutions of the classical Yang-Baxter equation (CYBE), 2) skew-symmetric, 3) nilpotent and 4) abelian. Hence these should be called abelian Jordanian deformations. As a result, the gravity duals are shown to be integrable deformations of AdS(5)xS(5). Then, abelian twists of AdS(5) are also investigated. These results provide a support for the gravity/CYBE correspondence proposed in arXiv:1404.1838.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2014)163
  DOI ID：10.1007/JHEP06(2014)163, ISSN：1029-8479, ORCID：48400311, arXiv ID：arXiv:1404.3657, Web of Science ID：WOS:000338644700001
• A deformation of quantum affine algebra in squashed Wess-Zumino-Novikov-Witten models　　　　　　　　　　　　　　　
  Io Kawaguchi; Kentaroh Yoshida
  JOURNAL OF MATHEMATICAL PHYSICS, 巻：55, 号：6, 開始ページ：062302, 2014年06月, ［査読有り］
  We proceed to study infinite-dimensional symmetries in two-dimensional squashed Wess-Zumino-Novikov-Witten models at the classical level. The target space is given by squashed S-3 and the isometry is SU(2)(L) x U(1)(R). It is known that SU(2)(L) is enhanced to a couple of Yangians. We reveal here that an infinite-dimensional extension of U(1)(R) is a deformation of quantum affine algebra, where a new deformation parameter is provided with the coefficient of the Wess-Zumino term. Then we consider the relation between the deformed quantum affine algebra and the pair of Yangians from the viewpoint of the left-right duality of monodromy matrices. The integrable structure is also discussed by computing the r/s-matrices that satisfy the extended classical Yang-Baxter equation. Finally, two degenerate limits are discussed. (C) 2014 AIP Publishing LLC.
  AMER INST PHYSICS, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1063/1.4880341
  DOI ID：10.1063/1.4880341, ISSN：0022-2488, eISSN：1089-7658, ORCID：48400398, arXiv ID：arXiv:1311.4696, Web of Science ID：WOS:000338634500019
• A Jordanian deformation of AdS space in type IIB supergravity　　　　　　　　　　　　　　　
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：146, 2014年06月, ［査読有り］
  We consider a Jordanian deformation of the AdS(5)xS(5) superstring action by taking a simple R-operator which satisfies the classical Yang-Baxter equation. The metric and NS-NS two-form are explicitly derived with a coordinate system. Only the AdS part is deformed and the resulting geometry contains the 3D Schrodinger spacetime as a subspace. Then we present the full solution in type IIB supergravity by determining the other field components. In particular, the dilaton is constant and a R-R three-form field strength is turned on. The symmetry of the solution is [SL(2, R) x U(1)(2)] x [SU(3) x U(1)] and contains an anisotropic scale symmetry.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2014)146
  DOI ID：10.1007/JHEP06(2014)146, ISSN：1029-8479, ORCID：48400295, arXiv ID：arXiv:1402.6147, Web of Science ID：WOS:000338663800001
• Schwinger pair production rate in confining theories via holography　　　　　　　　　　　　　　　
  Daisuke Kawai; Yoshiki Sato; Kentaroh Yoshida
  PHYSICAL REVIEW D, 巻：89, 号：10, 開始ページ：101901, 2014年05月, ［査読有り］
  We study the Schwinger pair production in confining theories. The production rate in an external electric field E is numerically evaluated by using the holographic description. There exist two kinds of critical values of the electric field: (i) E = E-c, above which there is no potential barrier and particles are freely generated, and (ii) E = E-s, below which the confining string tension dominates the electric field and the pair production does not occur. We argue the universal exponents associated with the critical behaviors.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.89.101901
  DOI ID：10.1103/PhysRevD.89.101901, ISSN：1550-7998, eISSN：1550-2368, ORCID：48400402, arXiv ID：arXiv:1312.4341, Web of Science ID：WOS:000336102200001
• Jordanian deformations of the AdS(5)xS(5) superstring　　　　　　　　　　　　　　　
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：153, 2014年04月, ［査読有り］
  We consider Jordanian deformations of the AdS(5)xS(5) superstring action. These deformations correspond to non-standard q-deformations. In particular, it is possible to perform a partial deformation, for example, of the AdS(5) part only, or of the S-5 part only. Then the classical action and the Lax pair are constructed with a linear, twisted and extended R operator. It is shown that the action preserves the kappa-symmetry.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2014)153
  DOI ID：10.1007/JHEP04(2014)153, ISSN：1029-8479, ORCID：48400400, arXiv ID：arXiv:1401.4855, Web of Science ID：WOS:000335453200001
• Anisotropic Landau-Lifshitz sigma models from q-deformed AdS<inf>5</inf>×S⁵ superstrings　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2014, 号：8, 2014年, ［査読有り］
  We consider bosonic subsectors of the q-deformed AdS<
  inf>
  5<
  /inf>
  ×S<
  sup>
  5<
  /sup>
  superstring action and study the classical integrable structure of anisotropic Landau-Lifshitz sigma models (LLSMs) derived by taking fast-moving string limits. The subsectors are 1) deformed AdS<
  inf>
  3<
  /inf>
  × S<
  sup>
  1<
  /sup>
  and 2) R × deformed S<
  sup>
  3<
  /sup>
  . The cases 1) and 2) lead to a time-like warped SL(2) LLSM and a squashed S<
  sup>
  3<
  /sup>
  LLSM, respectively. For each of them, we construct an infinite number of non-local conserved charges and show a quantum affine algebra at the classical level. Furthermore, a pp-wave like limit is applied for the case 1). The resulting system is a null-like warped SL(2) LLSM and exhibits a couple of Yangians through non-local gauge transformations associated with Jordanian twists.
  Springer Verlag, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP08(2014)110
  DOI ID：10.1007/JHEP08(2014)110, ISSN：1029-8479, SCOPUS ID：84917671436
• Integrable deformations of the AdS(5) x S-5 superstring and the classical Yang-Baxter equation - Towards the gravity/CYBE correspondence -　　　　　　　　　　　　　　　
  Takuya Matsumoto; Kentaroh Yoshida
  XXII INTERNATIONAL CONFERENCE ON INTEGRABLE SYSTEMS AND QUANTUM SYMMETRIES (ISQS-22), 巻：563, 号：1, 開始ページ：012020, 2014年, ［査読有り］
  Based on the formulation of Yang-Baxter sigma models developed by Klimcik and Delduc-Magro-Vicedo, we explain that various deformations of type JIB superstring on AdS(5) x S-5 can be charactered by classical r-matrices satisfying the classical Yang-Baxter equation (CYBE). The relation may be referred to as the gravity/CYBE correspondence. We present non-trivial examples of the correspondence including Lunin-Maldacena backgrounds for beta-deformations of the N = 4 super Yang-Mills theory and the gravity duals for non-commutative gauge theories. We also discuss non-integrable backgrounds such as AdS(5) x T-1,T-1 as a generalization.
  IOP PUBLISHING LTD, 英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1088/1742-6596/563/1/012020
  DOI ID：10.1088/1742-6596/563/1/012020, ISSN：1742-6588, ORCID：48400303, arXiv ID：arXiv:1410.0575, Web of Science ID：WOS:000346569200020
• Universal aspects of holographic Schwinger effect in general backgrounds　　　　　　　　　　　　　　　
  Yoshiki Sato; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：12, 号：12, 開始ページ：051, 2013年12月, ［査読有り］
  We consider universal aspects of a holographic Schwinger effect in general backgrounds with an external homogeneous electric field. The argument is based on the potential analysis developed in our previous work. Under some conditions, there always exists a critical electric field, above which the potential barrier vanishes and the system becomes unstable catastrophically. The critical value agrees with the one obtained from the Dirac-Born-Infeld action. For general confining backgrounds, we show that the Schwinger effect does not occur when the electric field is weaker than the confining string tension.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP12(2013)051
  DOI ID：10.1007/JHEP12(2013)051, ISSN：1029-8479, ORCID：48400301, arXiv ID：arXiv:1309.4629, Web of Science ID：WOS:000328336000001
• Dynamical F-strings intersecting D2-branes in type IIA supergravity　　　　　　　　　　　　　　　
  Kunihito Uzawa; Kentaroh Yoshida
  PHYSICAL REVIEW D, 巻：88, 号：6, 開始ページ：066005, 2013年09月, ［査読有り］
  We present time-dependent exact solutions composed of F-strings intersecting D2-branes in type IIA supergravity. The F-strings tend to approach each other with time in the six-dimensional space transverse to both F-strings and D2-branes. In general, a singularity appears before collision. An exceptional case is that the charges are the same and five directions in the transverse space are smeared out. Then we argue some applications of the solutions in building cosmological models. The possible models are classified based on compactifications of the internal space. All of them give rise to the Friedmann-Robertson-Walker universe with a power-law expansion.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.88.066005
  DOI ID：10.1103/PhysRevD.88.066005, ISSN：1550-7998, ORCID：48400340, arXiv ID：arXiv:1307.3093, Web of Science ID：WOS:000324306700006
• Holographic Schwinger effect in confining phase　　　　　　　　　　　　　　　
  Yoshiki Sato; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：09, 号：9, 開始ページ：134, 2013年09月, ［査読有り］
  We consider the Schwinger effect in confining phase by using a holographic setup. The potential analysis is performed for the confining D3-brane and D4-brane backgrounds. We find the critical electric field above which there is no potential barrier and the system becomes unstable catastrophically. An intriguing point is that no Schwinger effect occurs when the electric field is smaller than the confining string tension.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP09(2013)134
  DOI ID：10.1007/JHEP09(2013)134, ISSN：1029-8479, ORCID：48400302, arXiv ID：arXiv:1306.5512, Web of Science ID：WOS:000324890400001
• Schrodinger sigma models and Jordanian twists　　　　　　　　　　　　　　　
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：08, 号：8, 開始ページ：013, 2013年08月, ［査読有り］
  We proceed to study the integrable structures of two-dimensional nonlinear sigma models defined on three-dimensional Schrodinger spacetimes. We show that anisotropic Lax pairs are equivalent with isotropic Lax pairs with flat conserved currents under non-local gauge transformations. Then a quite non-trivial realization of the undeformed Yangian symmetry Y(sl(2)) is revealed after an appropriate gauge fixing, which is determined by comparing the gauge transformation to a quantum Jordanian twist. As a result, an exotic symmetry found in [arXiv:1209.4147] may be interpreted as a Jordanian deformation of Y(sl(2)).
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP08(2013)013
  DOI ID：10.1007/JHEP08(2013)013, ISSN：1029-8479, ORCID：48400378, arXiv ID：arXiv:1305.6556, Web of Science ID：WOS:000324113700013
• Potential analysis in holographic Schwinger effect　　　　　　　　　　　　　　　
  Yoshiki Sato; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：08, 号：8, 開始ページ：002, 2013年08月, ［査読有り］
  We analyze electrostatic potentials in the holographic Schwinger effect. The potential barrier for the pair production is estimated by a static potential consisting of static mass energies, an electric potential from an external electric-field, and the Coulomb potential between a particle and an antiparticle. Given that the Coulomb potential is supposed to be evaluated by the minimal surface attaching on the conformal boundary as usual, the critical field, where the potential barrier vanishes, exhibits a deviation of 30% from the one obtained from the Dirac-Born-Infeld (DBI) action. We reconsider this issue by reexamining the Coulomb-potential part, which is evaluated by the classical action of a string solution attaching on a probe D3-brane sitting at an intermediate position in the bulk AdS. Then the resulting critical-field completely agrees with the DBI result. This agreement gives rise to a strong support for the holographic scenario. We also discuss the finite-temperature case and the temperature-dependent critical-field also agrees with the DBI result.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP08(2013)002
  DOI ID：10.1007/JHEP08(2013)002, ISSN：1029-8479, ORCID：48400297, arXiv ID：arXiv:1304.7917, Web of Science ID：WOS:000324113700002
• String theories on warped AdS backgrounds and integrable deformations of spin chains　　　　　　　　　　　　　　　
  Takashi Kameyama; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：05, 号：5, 開始ページ：146, 2013年05月, ［査読有り］
  We study integrable deformations of AdS/CFT by focusing upon three kinds of warped AdS(3) geometries, 1) space-like warped AdS(3), 2) time-like warped AdS(3) and 3) null warped AdS(3). These geometries are embedded into type IIB supergravity solutions and are regarded as consistent string backgrounds. by restricting the classical motion of strings on the warped AdS(3) x S-1 subspace, the Landau-Lifshitz sigma models are derived by taking the fast-moving limit. The first two warped AdS(3) spaces correspond to anisotropic deformations of the sl(2) spin chain and the last one to Jordanian deformations. After taking the continuum limit of the deformed spin chains with coherent states, the resulting theories agree with the Landau-Lifshitz sigma models obtained from the string-theory side.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP05(2013)146
  DOI ID：10.1007/JHEP05(2013)146, ISSN：1029-8479, ORCID：48400288, arXiv ID：arXiv:1304.1286, Web of Science ID：WOS:000321375600063
• Dynamical Lifshitz-type solutions and aging phenomena　　　　　　　　　　　　　　　
  Kunihito Uzawa; Kentaroh Yoshida
  PHYSICAL REVIEW D, 巻：87, 号：10, 開始ページ：106003, 2013年05月, ［査読有り］
  We consider time-dependent Lifshitz-type solutions in type IIB supergravity. The solutions describe a time evolution from Lifshitz spacetimes to AdS spaces. We argue the holographic relation of them to aging phenomena in condensed matter physics. The solutions have no time-translation invariance and possess the dynamical scaling symmetry with z(c) = 2. In addition, the time evolution corresponds to slow (nonexponential) dynamics from nonequilibrium states to the equilibrium. We also discuss a mechanism of quantum quench to generate nonequilibrium states.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.87.106003
  DOI ID：10.1103/PhysRevD.87.106003, ISSN：1550-7998, ORCID：48400290, arXiv ID：arXiv:1302.5224, Web of Science ID：WOS:000318689800002
• Holographic description of the Schwinger effect in electric and magnetic field　　　　　　　　　　　　　　　
  Yoshiki Sato; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2013, 号：4, 開始ページ：1, 終了ページ：14, 2013年04月, ［査読有り］
  We consider a generalization of the holographic Schwinger effect proposed by Semenoff and Zarembo to the case with constant electric and magnetic fields. There are two ways to turn on magnetic fields, i) the probe D3-brane picture and ii) the string world-sheet picture. In the former picture, magnetic fields both perpendicular and parallel to the electric field are activated by a Lorentz transformation and a spatial rotation. In the latter one, the classical solutions of the string world-sheet corresponding to circular Wilson loops is generalized to contain two additional parameters encoding the presence of magnetic fields.
  Springer Verlag, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2013)111
  DOI ID：10.1007/JHEP04(2013)111, ISSN：1029-8479, ORCID：48400369, arXiv ID：arXiv:1303.0112, SCOPUS ID：84928254158
• Exotic symmetry and monodromy equivalence in Schrodinger sigma models　　　　　　　　　　　　　　　
  Io Kawaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：02, 号：2, 開始ページ：024, 2013年02月, ［査読有り］
  We consider the classical integrable structure of two-dimensional non-linear sigma models with target space three-dimensional Schrodinger spacetimes. There are the two descriptions to describe the classical dynamics: 1) the left description based on SL(2,R)(L) and 2) the right description based on U(1)(R). We have shown the sl(2,R)(L) Yangian and q-deformed Poincare algebras associated with them. We proceed to argue an infinite-dimensional extension of the q-deformed Poincare algebra. The corresponding charges are constructed by using a non-local map from the flat conserved currents related to the Yangian. The exotic tower structure of the charges is revealed by directly computing, the classical Poisson brackets. Then the monodromy matrices in both descriptions are shown to be gauge-equivalent via the relation between the spectral parameters. We also give a simple Riemann sphere interpretation of this equivalence.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP02(2013)024
  DOI ID：10.1007/JHEP02(2013)024, ISSN：1029-8479, ORCID：48400347, arXiv ID：arXiv:1209.4147, Web of Science ID：WOS:000316272900024
• Universal description of viscoelasticity with foliation preserving diffeomorphisms　　　　　　　　　　　　　　　
  Tatsuo Azeyanagi; Masafumi Fukuma; Hikaru Kawai; Kentaroh Yoshida
  Journal of Physics: Conference Series, 巻：462, 号：1, 開始ページ：012013, 2013年, ［査読有り］
  We review our recent proposal for a universal description of generic single-component viscoelastic systems with a single relaxation time. Foliation preserving diffeomorphisms are introduced as an underlying symmetry which naturally interpolates between the two extreme characters of elasticity and fluidity. The symmetry is found to be powerful enough to determine the dynamics in the first order of strains.
  Institute of Physics Publishing, 英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1088/1742-6596/462/1/012013
  DOI ID：10.1088/1742-6596/462/1/012013, ISSN：1742-6596, ORCID：48400329, arXiv ID：arXiv:1004.3899, SCOPUS ID：84891782023
• Supersymmetric Extensions of Non-Relativistic Scaling Algebras　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  SYMMETRY-BASEL, 巻：4, 号：3, 開始ページ：517, 終了ページ：536, 2012年09月, ［査読有り］
  An exciting subject in string theory is to consider some applications of the AdS/CFT correspondence to realistic systems like condensed matter systems. Since most of such systems are non-relativistic, an anisotropic scaling symmetry with the general value of dynamical critical exponent z plays an important role in constructing the gravity duals for non-relativistic field theories. Supersymmetric extensions of symmetry algebras including the anisotropic scaling are very helpful to consider holographic relations accurately. We give a short summary on the classification of super algebras with the anisotropic scaling as subalgebras of the following Lie superalgebras, psu(2,2 vertical bar 4), osp(8 vertical bar 4) and osp (8*vertical bar 4), which appear in the study of AdS/CFT in type IIB string and M theories. It contains supersymmetric extensions of Schrodinger algebra and Lifshitz algebra.
  MDPI AG, 英語
  DOI：https://doi.org/10.3390/sym4030517
  DOI ID：10.3390/sym4030517, ISSN：2073-8994, ORCID：48400312, Web of Science ID：WOS:000208832700009
• On the classical equivalence of monodromy matrices in squashed sigma model　　　　　　　　　　　　　　　
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：082, 2012年06月, ［査読有り］
  We proceed to study the hybrid integrable structure in two-dimensional non-linear sigma models with target space three-dimensional squashed spheres. A quantum affine algebra and a pair of Yangian algebras are realized in the sigma models and, according to them, there are two descriptions to describe the classical dynamics 1) the trigonometric description and 2) the rational description, respectively. For every description, a Lax pair is constructed and the associated monodromy matrix is also constructed. In this paper we show the gauge-equivalence of the monodromy matrices in the trigonometric and rational description under a certain relation between spectral parameters and the rescalings of sl(2) generators.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2012)082
  DOI ID：10.1007/JHEP06(2012)082, ISSN：1029-8479, ORCID：48400316, arXiv ID：arXiv:1203.3400, Web of Science ID：WOS:000306416500083
• The classical origin of quantum affine algebra in squashed sigma models　　　　　　　　　　　　　　　
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：115, 2012年04月, ［査読有り］
  We consider a quantum affine algebra realized in two-dimensional non-linear sigma models with target space three-dimensional squashed sphere. Its affine generators are explicitly constructed and the Poisson brackets are computed. The defining relations of quantum affine algebra in the sense of the Drinfeld first realization are satisfied at classical level. The relation to the Drinfeld second realization is also discussed including higher conserved charges. Finally we comment on a semiclassical limit of quantum affine algebra at quantum level.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP04(2012)115
  DOI ID：10.1007/JHEP04(2012)115, ISSN：1029-8479, ORCID：48400314, arXiv ID：arXiv:1201.3058, Web of Science ID：WOS:000304148100041
• On the classical equivalence of monodromy matrices in squashed sigma model
  Io Kawaguchi; Takuya Matsumoto; Kentaroh Yoshida
  Journal of High Energy Physics, 巻：2012, 号：6, 開始ページ：180, 2012年, ［査読有り］
  We proceed to study the hybrid integrable structure in two-dimensional nonlinear sigma models with target space three-dimensional squashed spheres. A quantum affine algebra and a pair of Yangian algebras are realized in the sigma models and, according to them, there are two descriptions to describe the classical dynamics 1) the trigonometric description and 2) the rational description, respectively. For every description, a Lax pair is constructed and the associated monodromy matrix is also constructed. In this paper we show the gauge-equivalence of the monodromy matrices in the trigonometric and rational description under a certain relation between spectral parameters and the rescalings of sl(2) generators. © 2012 SISSA.
  Springer Verlag, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP06(2012)082
  DOI ID：10.1007/JHEP06(2012)082, ISSN：1029-8479, ORCID：48400395, SCOPUS ID：84864267201
• Hybrid classical integrable structure of squashed sigma models - a short summary　　　　　　　　　　　　　　　
  Io Kawaguchi; Kentaroh Yoshida
  7TH INTERNATIONAL CONFERENCE ON QUANTUM THEORY AND SYMMETRIES (QTS7), 巻：343, 開始ページ：012055, 2012年, ［査読有り］
  We give a short summary of our recent works on the classical integrable structure of two-dimensional non-linear sigma models defined on squashed three-dimensional spheres. There are two descriptions to describe the classical dynamics, 1) the rational description and 2) the trigonometric description. It is possible to construct two different types of Lax pairs depending on the descriptions, and the classical integrability is shown by computing classical r/s-matrices satisfying the extended Yang-Baxter equation in both descriptions. In the former the system is described as an integrable system of rational type. On the other hand, in the latter it is described as trigonometric type. There exists a non-local map between the two descriptions and those are equivalent. This is a non-local generalization of the left-right duality in principal chiral models.
  IOP PUBLISHING LTD, 英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1088/1742-6596/343/1/012055
  DOI ID：10.1088/1742-6596/343/1/012055, ISSN：1742-6588, ORCID：48400317, arXiv ID：arXiv:1110.6748, Web of Science ID：WOS:000301174100054
• Classical integrability of Schrödinger sigma models and q-deformed Poincaré symmetry　　　　　　　　　　　　　　　
  Kawaguchi Io; Yoshida Kentaroh
  Journal of High Energy Physics, 巻：11, 号：11, 開始ページ：094, 2011年11月, ［査読有り］
  We discuss classical integrable structure of two-dimensional sigma models which have three-dimensional Schrödinger spacetimes as target spaces. The Schrödinger spacetimes are regarded as null-like deformations of AdS3. The original AdS3 isometry SL(2, R)L × SL(2, R)R is broken to SL(2, R)L × U(1)R due to the deformation. According to this symmetry, there are two descriptions to describe the classical dynamics of the system, 1) the SL(2, R)L description and 2) the enhanced U(1)R description. In the former 1), we show that the Yangian symmetry is realized by improving the SL(2, R)L Noether current. Then a Lax pair is constructed with the improved current and the classical inte-grability is shown by deriving the r/s-matrix algebra. In the latter 2), we find a non-local current by using a scaling limit of warped AdS3 and that it enhances U(1)R to a q-deformed Poincaré algebra. Then another Lax pair is presented and the corresponding r/s-matrices are also computed. The two descriptions are equivalent via a non-local map.
  Springer-Verlag, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP11(2011)094
  DOI ID：10.1007/JHEP11(2011)094, ISSN：1029-8479, CiNii Articles ID：120003726123, CiNii Books ID：AA11380940, ORCID：48400406, arXiv ID：arXiv:1109.0872, Web of Science ID：WOS:000297572500059
• Hybrid classical integrability in squashed sigma models　　　　　　　　　　　　　　　
  Io Kawaguchi; Kentaroh Yoshida
  PHYSICS LETTERS B, 巻：705, 号：3, 開始ページ：251, 終了ページ：254, 2011年11月, ［査読有り］
  We show that SU(2)(L) Yangian and q-deformed SU(2)(R) symmetries are realized in a two-dimensional sigma model defined on a three-dimensional squashed sphere. These symmetries enable us to develop the two descriptions to describe its classical dynamics, 1) rational and 2) trigonometric descriptions. The former 1) is based on the SU(2)(L) symmetry and the latter 2) comes from the broken SU(2)(R) symmetry. Each of the Lax pairs constructed in both ways leads to the same equations of motion. The two descriptions are related to one another through a non-local map. (C) 2011 Published by Elsevier B.V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2011.09.117
  DOI ID：10.1016/j.physletb.2011.09.117, ISSN：0370-2693, ORCID：48400383, arXiv ID：arXiv:1107.3662, Web of Science ID：WOS:000297180700015
• Super Yangian of superstring on AdS(5) x S-5 revisited　　　　　　　　　　　　　　　
  Machiko Hatsuda; Kentaroh Yoshida
  ADVANCES IN THEORETICAL AND MATHEMATICAL PHYSICS, 巻：15, 号：5, 開始ページ：1485, 終了ページ：1501, 2011年10月, ［査読有り］
  We construct infinite number of conserved nonlocal charges for type IIB superstring on the AdS(5)xS(5) space in the conformal gauge without assuming any. gauge fixing, and show that they satisfy the super Yangian algebra. The resultant algebra is the same as our previous work [8], where a special gauge was assumed in such a way that the Noether current satisfies a flatness condition. However the flatness condition for the Noether current of a superstring on the AdS space is broken in general. We show that the anomalous contribution is absorbed into the current where fermionic constraints play an essential role, and a resultant conserved nonlocal charge has different expression satisfying the same super Yangian algebra.
  INT PRESS BOSTON, INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.4310/ATMP.2011.v15.n5.a6
  DOI ID：10.4310/ATMP.2011.v15.n5.a6, ISSN：1095-0761, ORCID：48400285, arXiv ID：arXiv:1107.4673, Web of Science ID：WOS:000208587100006
• Yangian symmetry in deformed WZNW models on squashed spheres　　　　　　　　　　　　　　　
  Io Kawaguchi; Domenico Orlando; Kentaroh Yoshida
  PHYSICS LETTERS B, 巻：701, 号：4, 開始ページ：475, 終了ページ：480, 2011年07月, ［査読有り］
  We introduce a deformation of the Wess-Zumino-Novikov-Witten model with three-dimensional squashed sphere target space. We show how with an appropriate choice of Wess-Zumino and boundary terms it is possible to construct an infinite family of conserved charges realizing an SU(2) Yangian. Finally we discuss the running of the squashing parameter under renormalization group flow. (C) 2011 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2011.06.007
  DOI ID：10.1016/j.physletb.2011.06.007, ISSN：0370-2693, ORCID：48400324, arXiv ID：arXiv:1104.0738, Web of Science ID：WOS:000292994100015
• Semiclassical analysis of M2-brane in AdS(4)xS(7)/Z(k)　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Hyeonjoon Shin; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：12, 号：12, 開始ページ：012, 2010年12月, ［査読有り］
  We start from the classical action describing a single M2-brane on AdS(4)xS(7)/Z(k) and consider semiclassical fluctuaitions around a static, 1/2 BPS configuration whose shape is AdS(2)xS(1). The internal manifold S-7/Z(k) is described as a U(1) fibration over CP3 and the static configuration is wrapped on the U(1) fiber. Then the configuration is reduced to an AdS(2) world-sheet of type IIA string on AdS(4)xCP(3) through the Kaluza-Klein reduction on S-1. It is shown that the fluctuations form an infinite set of N = 1 supermultiplets on AdS(2) for k = 1, 2. The set is invariant under SO(8) which may be consistent with N = 8 supersymmetry on AdS(2). We discuss the behavior of the fluctuations around the boundary of AdS(2) and its relation to deformations of Wilson loop operator.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP12(2010)012
  DOI ID：10.1007/JHEP12(2010)012, ISSN：1029-8479, ORCID：48400380, arXiv ID：arXiv:1007.3354, Web of Science ID：WOS:000285964400034
• Hidden Yangian symmetry in sigma model on squashed sphere　　　　　　　　　　　　　　　
  Io Kawaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：11, 号：11, 開始ページ：032, 2010年11月, ［査読有り］
  We discuss a hidden symmetry of a two-dimensional sigma model on a squashed S-3. The SU(2) current can be improved so that it can be regarded as a flat connection. Then we can obtain an infinite number of conserved non-local charges and show the Yangian algebra by directly checking the Serre relations. This symmetry is also deduced from the coset structure of the squashed sphere. The same argument is applicable to the warped AdS(3) spaces by the double Wick rotations.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/JHEP11(2010)032
  DOI ID：10.1007/JHEP11(2010)032, ISSN：1029-8479, ORCID：48400408, arXiv ID：arXiv:1008.0776, Web of Science ID：WOS:000284963400049
• Universal description of viscoelasticity with foliation preserving diffeomnorphisms　　　　　　　　　　　　　　　
  Tatsuo Azeyanagi; Masafumi Fukuma; Hikaru Kawai; Kentaroh Yoshida
  PHYSICS LETTERS B, 巻：681, 号：3, 開始ページ：290, 終了ページ：295, 2009年11月, ［査読有り］
  A universal description is proposed for generic viscoelastic systems with a single relaxation time. Foliation preserving diffeomorphisms are introduced as an underlying symmetry which naturally interpolates between the two extreme limits of elasticity and fluidity. The symmetry is found to be powerful enough to determine the dynamics in the first order of strains. (C) 2009 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2009.10.027
  DOI ID：10.1016/j.physletb.2009.10.027, ISSN：0370-2693, ORCID：48400313, arXiv ID：arXiv:0907.0656, Web of Science ID：WOS:000271849900017
• Asymptotic symmetries of Schrodinger spacetimes　　　　　　　　　　　　　　　
  Geoffrey Compere; Sophie de Buyl; Stephane Detournay; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：10, 号：10, 開始ページ：032, 2009年10月, ［査読有り］
  We discuss the asymptotic symmetry algebra of the Schrodinger -invariant metrics in d + 3 dimensions and its realization on finite temperature solutions of gravity coupled to matter fields. These solutions have been proposed as gravity backgrounds dual to non-relativistic CFTs with critical exponent z in d space dimensions. It is known that the Schrodinger algebra possesses an infinite-dimensional extension, the Schrodinger-Virasoro algebra. However, we show that the asymptotic symmetry algebra of Schrodinger space-times is only isomorphic to the exact symmetry group of the background. It is possible to construct from first principles finite and integrable charges that infinite-dimensionally extend the Schrodinger algebra but these charges are not correctly represented via a Dirac bracket. We briefly comment on the extension of our analysis to spacetimes with Lifshitz symmetry.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2009/10/032
  DOI ID：10.1088/1126-6708/2009/10/032, ISSN：1029-8479, ORCID：48400318, arXiv ID：arXiv:0908.1402, Web of Science ID：WOS:000271542800032
• Coset construction for duals of non-relativistic CFTs　　　　　　　　　　　　　　　
  Sakura Schaefer-Nameki; Masahito Yamazaki; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：05, 号：5, 開始ページ：038, 2009年05月, ［査読有り］
  We systematically analyze backgrounds that are holographic duals to non-relativistic CFTs, by constructing them as cosets of the Schrodinger group and variants thereof. These cosets G/H are generically non-reductive and we discuss in generality how a metric on such spaces can be determined from a non-degenerate H-invariant symmetric two-form. Applying this to the d = 2 Schrodinger algebra, we reproduce the five-dimensional backgrounds proposed as duals of fermions at unitarity, and under reasonable physical assumptions, we demonstrate uniqueness of this background. The proposed gravity dual of the Lifshitz fixed-point, for which Galileian symmetry is absent, also fits into this organizational scheme and uniqueness of this background can also be shown.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2009/05/038
  DOI ID：10.1088/1126-6708/2009/05/038, ISSN：1029-8479, ORCID：48400361, arXiv ID：arXiv:0903.4245, Web of Science ID：WOS:000267789100038
• Non-relativistic M2-brane gauge theory and new superconformal algebra　　　　　　　　　　　　　　　
  Yu Nakayama; Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：096, 2009年04月, ［査読有り］
  We study non-relativistic limits of the N = 6 Chern-Simons-Matter theory that arises as a low-energy limit of the M2-brane gauge theory with background flux. The model admits several different non-relativistic limits and we find that the maximal supersymmetry we construct has 14 components of supercharges, which is a novel example of non-relativistic superconformal algebra in (1 + 2) dimension. We also investigate the other limits that realize less supersymmetries.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2009/04/096
  DOI ID：10.1088/1126-6708/2009/04/096, ISSN：1029-8479, ORCID：48400349, arXiv ID：arXiv:0902.2204, Web of Science ID：WOS:000266428300096
• Interacting SUSY-singlet matter in non-relativistic Chern-Simons theory　　　　　　　　　　　　　　　
  Yu Nakayama; Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 巻：42, 号：19, 開始ページ：195402, 2009年03月, ［査読有り］
  We construct an example of supersymmetric Chern-Simons-matter theory with a matter field transforming as a singlet representation of the supersymmetry algebra, where the bosonic and fermionic degrees of freedom do not match. This is obtained as a non-relativistic limit of the N = 2 Chern-Simons-matter theory in 1+2 dimensions, where the particle and anti-particle coexist. We also study the index to investigate the mismatch of bosonic and fermionic degrees of freedom.
  IOP PUBLISHING LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1751-8113/42/19/195402
  DOI ID：10.1088/1751-8113/42/19/195402, ISSN：1751-8113, ORCID：48400351, arXiv ID：arXiv:0812.1564, Web of Science ID：WOS:000265815000020
• A family of super Schrodinger invariant Chern-Simons matter systems　　　　　　　　　　　　　　　
  Yu Nakayama; Shinsei Ryu; Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：01, 号：1, 開始ページ：006, 2009年01月, ［査読有り］
  We investigate non-relativistic limits of the N=3 Chern-Simons matter system in 1+2 dimensions. The relativistic theory can generate several inequivalent super Schodinger invariant theories, depending on the degrees of freedom we choose to retain in the non-relativistic limit. The maximally supersymmetric Schrodinger invariant theory is obtained by keeping all particle degrees of freedom. The other descendants, where particles and anti-particles coexist, are also Schrodinger invariant but preserve less supersymmetries. Thus, we have a family of super Schrodinger invariant field theories produced from the parent relativistic theory.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2009/01/006
  DOI ID：10.1088/1126-6708/2009/01/006, ISSN：1029-8479, ORCID：48400382, arXiv ID：arXiv:0811.2461, Web of Science ID：WOS:000265578400006
• Families of IIB duals for nonrelativistic CFTs　　　　　　　　　　　　　　　
  Sean A. Hartnoll, Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：12, 号：12, 開始ページ：071, 2008年12月, ［査読有り］
  We show that the recent string theory embedding of a spacetime with nonrelativistic Schrodinger symmetry can be generalised to a twenty one dimensional family of solutions with that symmetry. Our solutions include IIB backgrounds with no three form flux turned on, and arise as near horizon limits of branewave spacetimes. We show that there is a hypersurface in the space of these theories where an instability appears in the gravitational description, indicating a phase transition in the nonrelativistic field theory dual. We also present simple embeddings of duals for nonrelativistic critical points where the dynamical critical exponent can take many values z not equal 2.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2008/12/071
  DOI ID：10.1088/1126-6708/2008/12/071, ISSN：1029-8479, ORCID：48400277, arXiv ID：arXiv:0810.0298, Web of Science ID：WOS:000265578300071
• Super Schrodinger algebra in AdS/CFT　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF MATHEMATICAL PHYSICS, 巻：49, 号：10, 開始ページ：102302, 2008年10月, ［査読有り］
  We discuss (extended) super-Schrodinger algebras obtained as subalgebras of the superconformal algebra psu(2,2 vertical bar 4). The Schrodinger algebra with two spatial dimensions can be embedded into so(4,2). In the superconformal case the embedded algebra may be enhanced to the so-called super-Schrodinger algebra. In fact, we find an extended super-Schrodinger subalgebra of psu(2,2 vertical bar 4). It contains 24 supercharges (i.e., 3/4 of the original supersymmetries) and the generators of so(6), as well as the generators of the original Schrodinger algebra. In particular, the 24 supercharges come from 16 rigid supersymmetries and half of 16 superconformal ones. Moreover, this superalgebra contains a smaller super-Schrodinger subalgebra, which is a supersymmetric extension of the original Schrodinger algebra and so(6) by eight supercharges (half of 16 rigid supersymmetries). It is still a subalgebra even if there are no so (6) generators. We also discuss super-Schrodinger subalgebras of the superconformal algebras, osp(8 vertical bar 4) and osp(8*vertical bar 4), and find super Schrodinger subalgebras in the same way. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2998205]
  AMER INST PHYSICS, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1063/1.2998205
  DOI ID：10.1063/1.2998205, ISSN：0022-2488, ORCID：48400339, arXiv ID：arXiv:0805.2661, Web of Science ID：WOS:000260572600014
• More super Schrodinger algebras from psu(2,2 vertical bar 4)　　　　　　　　　　　　　　　
  Makato Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：08, 号：8, 開始ページ：049, 2008年08月, ［査読有り］
  We discuss super Schrodinger algebras with less supercharges from N=4 superconformal algebra psu(2, 2 vertical bar 4). Firstly N= 2 and N= 1 superconformal algebras are constructed from the psu(2, 2 vertical bar 4) via projection operators. Then a super Schrodinger subalgebra is found from each of them. The one obtained from N= 2 has 12 supercharges with su(2)(2) x u(1) and the other from N=1 has 6 supercharges with u(1)(3). By construction, those are still subalgebras of psu(2, 2 vertical bar 4). Another super Schrodinger algebra, which preserves 6 supercharges with a single u(1) symmetry, is also obtained from N=1 superconformal algebra su(2, 2 vertical bar 1). In particular, it coincides with the symmetry of N=2 non-relativistic Chern-Simons matter system in three dimensions.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2008/08/049
  DOI ID：10.1088/1126-6708/2008/08/049, ISSN：1029-8479, ORCID：48400332, arXiv ID：arXiv:0806.3612, Web of Science ID：WOS:000258917400060
• Noncommutative D-branes from covariant AdS superstring　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：797, 号：1-2, 開始ページ：179, 終了ページ：198, 2008年07月, ［査読有り］
  We study noncommutative (NC) D-branes on AdS(5) x S-5 from kappa-invariance of covariant Green-Schwarz action of an open string with a non-trivial world-volume flux. Finding boundary conditions to ensure the kappa-invariance, we can see possible configurations of the NC D-branes. With this method 1/4 BPS NC D-branes are discussed. The resulting NC Dp-branes are 1/4 BPS at arbitrary position other than the p = 1 case. The exceptional D-string is 1/2 BPS at the origin and 1/4 BPS outside the origin. Those are reduced to possible 1/4 BPS or 1/2 BPS Ads D-branes in the commutative limit. The same analysis is applied to an open superstring in a pp-wave and leads to 1/4 BPS configurations of NC D-branes. These D-branes are consistently obtained from AdS D-branes via the Penrose limit. (C) 2008 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2007.12.032
  DOI ID：10.1016/j.nuclphysb.2007.12.032, ISSN：0550-3213, ORCID：48400363, arXiv ID：hep-th/0604039, Web of Science ID：WOS:000255310000007
• A semiclassical string description of Wilson loop with local operators　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：798, 号：1-2, 開始ページ：72, 終了ページ：88, 2008年07月, ［査読有り］
  We discuss a semiclassical string description to circular Wilson loops without/with local operator insertions. Type IIB string theory on AdS(5) x S-5 is expanded around the corresponding classical solutions with respect to fluctuations and semiclassical quadratic actions are computed. Then the dual corresponding operators describing the fluctuations are discussed from the point of view of a small deformation of the Wilson loops. The result gives new evidence for AdS/CFT correspondence. (c) 2008 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2008.01.032
  DOI ID：10.1016/j.nuclphysb.2008.01.032, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400358, arXiv ID：arXiv:0709.4187, Web of Science ID：WOS:000255816200004
• Holography of non-relativistic string on AdS(5) x S-5　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 巻：23, 号：14-15, 開始ページ：2275, 終了ページ：2276, 2008年06月, ［査読有り］
  We briefly review a holography of non-relativistic (NR) string on AdS(5) x S-5. The NR string can be regarded as a semiclassical string around an AdS(2) classical solution corresponding to a straight Wilson line in the gauge-theory side. Exciting non-normalizable modes of the NR string gives source term insertions on the Wilson line. For normalizable modes we discuss a relation to a conformal quantum mechanics.
  WORLD SCIENTIFIC PUBL CO PTE LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1142/S0217751X08041062
  DOI ID：10.1142/S0217751X08041062, ISSN：0217-751X, ORCID：48400405, Web of Science ID：WOS:000257295200048
• Holography of rotating dual giant Wilson loops　　　　　　　　　　　　　　　
  Akitsugu Miwa; Yoske Sumitomo; Kentaroh Yoshida
  INTERNATIONAL JOURNAL OF MODERN PHYSICS A, 巻：23, 号：14-15, 開始ページ：2267, 終了ページ：2268, 2008年06月, ［査読有り］
  We briefly review a tunneling picture of rotating D3-brane solutions. By applying the "double Wick rotation" to the Lorentzian solutions, we construct Euclidean solutions. The solutions are composed of dual giant gravitons and spike D3-brane solutions, and their classical actions reproduce expectation values of the k-th symmetric Wilson loops as well as correlation functions of dual giant graviton operators as expected.
  WORLD SCIENTIFIC PUBL CO PTE LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1142/S0217751X08041037
  DOI ID：10.1142/S0217751X08041037, ISSN：0217-751X, ORCID：48400348, Web of Science ID：WOS:000257295200045
• A tunneling picture of dual giant Wilson loop　　　　　　　　　　　　　　　
  Akitsugu Miwa; Yoske Sumitomo; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：05, 号：5, 開始ページ：102, 2008年05月, ［査読有り］
  We further discuss a rotating dual giant Wilson loop (D3-brane) solution constructed in Lorentzian AdS by Drukker et al. The solution is shown to be composed of a dual giant Wilson loop and a dual giant graviton by minutely examining its shape. Hence it may be supposed that the dual gauge-theory operator should be a k-th symmetric Wilson loop with insertions of dual giant graviton operators. To give a convincing argument for this observation, the classical action of the solution should be evaluated in Euclidean signature. For this purpose we perform a Wick rotation to the Lorentzian solution by following the tunneling prescription and obtain Euclidean solutions attaching to a circle or a straight line on the AdS boundary. The classical action contains a logarithmic divergence which is proportional to the R-charge. It is consistent with the correlation function of the dual giant graviton operators. Because of ambiguities concerning regularization, finite terms of the action do not lead to conclusive evidence. However we may expect that the ambiguities would cancel by subtracting the action of the D3-brane with a straight-line boundary from that with a circular boundary. It is really shown that the difference is consistent with the expectation value of the k-th symmetric Wilson loop. Although our analysis does not specify the unique dual gauge-theory operator, we discuss possible candidates implied by the D3-brane computation.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2008/05/102
  DOI ID：10.1088/1126-6708/2008/05/102, ISSN：1029-8479, ORCID：48400385, arXiv ID：arXiv:0802.2735, Web of Science ID：WOS:000256664400101
• Constraints on the electroweak chiral Lagrangian from the precision data　　　　　　　　　　　　　　　
  Sukanta Dutta; Kaoru Hagiwara; Qi-Shu Yan; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：790, 号：1-2, 開始ページ：111, 終了ページ：137, 2008年02月, ［査読有り］
  In the framework of the effective field theory method, we use the experimental data and the perturbative unitarity bounds to determine the values and uncertainty of all the 11 chiral coefficients (alpha(i), i = 0,..., 10) of the standard electroweak chiral Lagrangian. Up to linear terms in alpha(i), we provide the one-loop renormalization group equations of all the chiral coefficients, which are calculated in the Feynman-'t Hooft gauge using the modified minimal subtraction scheme. With the improved renormalization group equations to sum over the logarithmic corrections, we analyze the current experimental uncertainty of oblique correction parameters, S(Lambda) and T(Lambda). We find that, due to the large uncertainty in the triple gauge-boson coupling measurements, the parameter space of positive S(Lambda) for Lambda > 1 TeV is still allowed by the current experimental data. T(Lambda) tends to increase with Lambda even in the presence of the operators that contribute to the triple and quartic gauge-boson couplings. (c) 2007 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2007.08.017
  DOI ID：10.1016/j.nuclphysb.2007.08.017, ISSN：0550-3213, ORCID：48400354, arXiv ID：arXiv:0705.2277, Web of Science ID：WOS:000251735500006
• Holography of non-relativistic string on AdS(5) x S-5　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：02, 号：2, 開始ページ：092, 2008年02月, ［査読有り］
  We discuss a holographic dual of a non-relativistic (NR) string on AdS(5) x S-5. The NR string can be regarded as a semiclassical string around an AdS(2) classical solution corresponding to a straight Wilson line in the gauge-theory side. The quadratic action with respect to the fluctuations is composed of free massive and massless scalars, and free massive fermions on the AdS(2) world-sheet. We show that the complete agreement of the spectra between the NR string and a conformal quantum mechanics (CQM). Then we show a holographic relation between normalizable modes of the NR string and wave functions in the CQM. Then it may be argued from this result that an AdS(2)/CFT1 would be realized in AdS(5)/CFT4. We can really discuss a GKPW-type relation by considering non-normalizable modes of the NR string in Euclidean signature. Those modes give a source term insertion to the Wilson line, which can also be regarded as a small deformation of it.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2008/02/092
  DOI ID：10.1088/1126-6708/2008/02/092, ISSN：1029-8479, ORCID：48400292, arXiv ID：arXiv:0712.4112, Web of Science ID：WOS:000254764400020
• Holography of non-relativistic string on AdS5XS5
  Makoto Sakaguchi; Kentaroh Yoshida
  AIP Conference Proceedings, 巻：1078, 開始ページ：468, 終了ページ：470, 2008年, ［査読有り］
  We review a holography of a non-relativistic (NR) string on AdS 5xS5. The NR string can be regarded as a semiclassical string around an AdS2 classical solution, which corresponds to a straight Wilson line in the gauge-theory side. Non-normalizable modes of the NR string correspond to string fluctuations reaching the boundary, and cause small deformations of the Wilson line. The operator inserted on the Wilson line are found from the small deformation of the Wilson line. Normahzable modes, which exist in the Lorentzian case, are considered as wave functions in a conformal quantum mechanics. © 2008 American Institute of Physics.
  英語, 研究論文（国際会議プロシーディングス）
  DOI：https://doi.org/10.1063/1.3051997
  DOI ID：10.1063/1.3051997, ISSN：0094-243X, ORCID：48400276, SCOPUS ID：63849184311
• Intersecting noncommutative M5-branes from covariant open supermembrane　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  NUCLEAR PHYSICS B, 巻：781, 開始ページ：85, 終了ページ：98, 2007年10月, ［査読有り］
  We study intersecting noncommutative (NC) M5-branes from K-invariance of an open supermembrane action with constant three-form fluxes. The K-invariance gives rise to possible D-brane configurations for which projection operators can be determined. We construct projection operators for two types of 1/4 BPS intersecting NC M5-branes. The one is an intersection of two NC M5-branes: NC M5 perpendicular to NC M5 (3). The other is that of an NC M5-brane and a commutative (C) M5-brane: NC M5 perpendicular to C M5 (1). An NC MS-brane can be viewed as a bound state of M5 and M2, and the configurations M2 perpendicular to M5 (1) and M2 perpendicular to M2 (0) are realized on the intersecting M5-branes. Taking a commutative limit the allowed intersecting M5-branes are surely reproduced: M5 perpendicular to M5 (3) and M5 perpendicular to M5 (1). (c) 2007 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2007.05.004
  DOI ID：10.1016/j.nuclphysb.2007.05.004, ISSN：0550-3213, ORCID：48400330, arXiv ID：hep-th/0702062, Web of Science ID：WOS:000249711100004
• Non-relativistic string and D-branes on AdS(5)xS(5) from semiclassical approximation　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：05, 号：5, 開始ページ：051, 2007年05月, ［査読有り］
  We show that non-relativistic actions of strings and D-branes on AdS(5) x S-5 can be reproduced as a semiclassical approximation of the string and D-brane actions around static 1/2 BPS configurations. This is contrastive to the Penrose limit. For example, the pp-wave string can be recaptured as a semiclassical approximation around a 1/2 BPS particle rotating at the velocity of light. We argue that small deformation of a straight Wilson line would give a composite operator in the gauge-theory side that corresponds to a semiclassical state of the non-relativistic string, according to the semiclassical interpretation.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2007/05/051
  DOI ID：10.1088/1126-6708/2007/05/051, ISSN：1029-8479, ORCID：48400373, arXiv ID：hep-th/0703061, Web of Science ID：WOS:000247030800051
• A covariant approach to noncommutative M5-branes　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT, 巻：171, 号：171, 開始ページ：275, 終了ページ：278, 2007年, ［査読有り］
  We briefly review how to discuss noncommutative (NC) M5-branes and intersecting NC M5-branes from k-invariance of an open supermembrane action with constant three-form fluxes. The K-invariance gives rise to possible Dirichlet brane configurations. We shortly summarize a construction of projection operators for NC M5-branes and some intersecting configurations of NC M5-branes. A strong flux limit of them is also discussed.
  PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1143/PTPS.171.275
  DOI ID：10.1143/PTPS.171.275, ISSN：0375-9687, ORCID：48400289, arXiv ID：hep-th/0702132, Web of Science ID：WOS:000254229300031
• Noncommutative M-branes from covariant open supermembranes　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  PHYSICS LETTERS B, 巻：642, 号：4, 開始ページ：400, 終了ページ：403, 2006年11月, ［査読有り］
  We discuss an open supermembrane in the presence of a constant three-form. The boundary conditions to ensure the K-invariance of the action lead to possible Dirichlet branes. It is shown that a noncommutative (NC) M5-brane is possible as a boundary and the self-duality condition that the flux on the world-volume satisfies is derived from the requirement of the K-symmetry. We also find that the open supermembrane can attach to each of infinitely many M2-branes on an M5-brane, namely a strong flux limit of the NC M5-brane. (c) 2006 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.physletb.2006.09.047
  DOI ID：10.1016/j.physletb.2006.09.047, ISSN：0370-2693, eISSN：1873-2445, ORCID：48400335, arXiv ID：hep-th/0608099, Web of Science ID：WOS:000242141300017
• Non-relativistic AdS branes and Newton-Hooke superalgebra　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：10, 号：10, 開始ページ：078, 2006年10月, ［査読有り］
  We examine a non-relativistic limit of D-branes in AdS(5) x S-5 and M-branes in AdS(4/7) x S-7/4. First, Newton-Hooke superalgebras for the AdS branes are derived from AdS x S superalgebras as Inonu-Wigner contractions. It is shown that the directions along which the AdS-brane worldvolume extends are restricted by requiring that the isometry on the AdS-brane worldvolume and the Lorentz symmetry in the transverse space naturally extend to the super-isometry. We also derive Newton-Hooke superalgebras for pp-wave branes and show that the directions along which a brane worldvolume extends are restricted. Then the Wess-Zumino terms of the AdS branes are derived by using the Chevalley-Eilenberg cohomology on the super-AdS x S algebra, and the non-relativistic limit of the AdS-brane actions is considered. We show that the consistent limit is possible for the following branes: Dp (even, even) for p = 1 mod 4 and Dp (odd, odd) for p = 3 mod 4 in AdS(5) x S-5, and M2 (0,3), M2 (2,1), M5 (1,5) and M5 (3,3) in AdS(4) x S-7 and S-4 x AdS(7). We furthermore present non-relativistic actions for the AdS branes.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2006/10/078
  DOI ID：10.1088/1126-6708/2006/10/078, ISSN：1029-8479, ORCID：48400366, arXiv ID：hep-th/0605124, Web of Science ID：WOS:000242714400012
• Higher loop Bethe ansatz for open spin-chains in AdS/CFT　　　　　　　　　　　　　　　
  Keisuke Okamura; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：09, 号：9, 開始ページ：081, 2006年09月, ［査読有り］
  We propose a perturbative asymptotic Bethe ansatz (PABA) for open spin-chain systems whose Hamiltonians are given by matrices of anomalous dimension for composite operators, and apply it to two types of composite operators related to two different brane configurations. One is an AdS(4) x S-2-brane in the bulk AdS(5) x S-5 which gives rise to a defect conformal field theory (dCFT) in the dual field theory, and the other is a giant graviton system with an open string excitation. In both cases, excitations on open strings attaching to D-branes (a D5-brane for the dCFT case, and a spherical D3-brane for the giant graviton case) can be represented by magnon states in the spin-chains with appropriate boundary conditions, in which informations of the D-branes are encoded. We concentrate on single-magnon problems, and explain how to calculate boundary S-matrices via the PABA technique. We also discuss the energy spectrum in the BMN limit.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2006/09/081
  DOI ID：10.1088/1126-6708/2006/09/081, ISSN：1029-8479, ORCID：48400299, arXiv ID：hep-th/0604100, Web of Science ID：WOS:000241020900002
• Dynamical aspects of the plane-wave matrix model at finite temperature　　　　　　　　　　　　　　　
  Naoyuki Kawahara; Jun Nishimura; Kentaroh Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：06, 号：6, 開始ページ：052, 2006年06月, ［査読有り］
  We study dynamical aspects of the plane-wave matrix model at finite temperature. One-loop calculation around general classical vacua is performed using the background field method, and the integration over the gauge field moduli is carried out both analytically and numerically. In addition to the trivial vacuum, which corresponds to a single M5-brane at zero temperature, we consider general static fuzzy-sphere type configurations. They are all 1/2 BPS, and hence degenerate at zero temperature due to supersymmetry. This degeneracy is resolved, however, at finite temperature, and we identify the configuration that gives the smallest free energy at each temperature. The Hagedorn transition in each vacuum is studied by using the eigenvalue density method for the gauge field moduli, and the free energy as well as the Polyakov line is obtained analytically near the critical point. This reveals the existence of fuzzy sphere phases, which may correspond to the plasma-ball phases in N = 4 SU( infinity) SYM on S-1 x S-3. We also perform Monte Carlo simulation to integrate over the gauge field moduli. While this confirms the validity of the analytic results near the critical point, it also shows that the trivial vacuum gives the smallest free energy throughout the high temperature regime.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2006/06/052
  DOI ID：10.1088/1126-6708/2006/06/052, ISSN：1029-8479, ORCID：48400328, arXiv ID：hep-th/0601170, Web of Science ID：WOS:000238850300014
• Point-like graviton scattering in plane-wave matrix model　　　　　　　　　　　　　　　
  H Shin; K Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：051, 2006年04月, ［査読有り］
  In a plane-wave matrix model we discuss a two-body scattering of gravitons in the SO(3) symmetric space. In this case the graviton solutions are point-like in contrast to the scattering in the SO(6) symmetric space where spherical membranes are interpreted as gravitons. We concentrate on a configuration in the 1-2 plane where a graviton rotates with a constant radius and the other one elliptically rotates. Then the one-loop effective action is computed by using the background field method. As the result, we obtain the 1/r(7)-type interaction potential, which strongly suggests that the scattering in the matrix model would be closely related to that in the light-front eleven-dimensional supergravity.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2006/04/051
  DOI ID：10.1088/1126-6708/2006/04/051, ISSN：1029-8479, ORCID：48400293, arXiv ID：hep-th/0511072, Web of Science ID：WOS:000237369000008
• Non-relativistic AdS branes　　　　　　　　　　　　　　　
  Makoto Sakaguchi; Kentaroh Yoshida
  Annual Meeting of the Division of Particles and Fields of the American Physical Society, DPF 2006, and the Annual Fall Meeting of the Japan Particle Physics Community, 2006年, ［査読有り］
  • NH superalgebras of branes in AdS5 × S5 and AdS4/7 × S7/4 - IW contraction of psu(2
  2|4) and osp(8(*)|4) - sub-superalgebra as super symmetrization of brane worldvolume isometry and transverse Lorentz symmetry. - classification of 1/2 supersymmetric subspaces ⊃ 1/2 BPS branes • Non-relativistic AdS brane actions - consistent limit can be performed for 1/2 BPS AdS branes - in flat limit they reproduce non-relativistic brane actions in flat spacetime comments on M-branes • Newton-Hooke superalgebras of M-branes in AdS 4/7 × S7/4 IW contraction of osp(8|4) or osp(8 *|4) (Table Presented) p-branes with p = 1 mod 4 are 1/2 BPS Dirichlet branes of open supermembrane [Yoshida-MS'0310,'0405]
  brane probe analysis [Kim-Yee'0211] • 2- and 5-branes admit consistent non-relativistic limit. - M2- and M5-brane actions are characterized as non-trivial elements of CE cohomology on osp(8|4) or osp(8*|4). - M2- and M5-branes admit consistent non-relativistic limit, and derived nonrelativistic AdS M-brane actions reproduce the non-relativistic M2-brane action [Gomis-Kamimura- Townsend'0409] and the linearized M5-brane action [Claus-Kallosh-Van Proeyen'9711] in flat limit.
  American Physical Society, 英語, 研究論文（国際会議プロシーディングス）
  SCOPUS ID：84907360630
• Dynamical generation of a single M5-brane in plane-wave matrix model at finite temperature　　　　　　　　　　　　　　　
  Yoshida Kentaroh
  素粒子論研究, 巻：113, 号：1, 開始ページ：A37, 2006年
  素粒子論グループ 素粒子論研究 編集部, 英語
  DOI：https://doi.org/10.24532/soken.113.1_A37
  DOI ID：10.24532/soken.113.1_A37, CiNii Articles ID：110004749548
• Open spinning strings and AdS/dCFT duality　　　　　　　　　　　　　　　
  K Okamura; Y Takayama; K Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：01, 号：1, 開始ページ：112, 2006年01月, ［査読有り］
  We consider open spinning string solutions on an AdS(4) x S-2-brane (D5-brane) in the bulk AdS(5) x S-5 background. By taking account of the breaking of SO(6) R to SO(3)(H) x SO(3)(V) due to the presence of the AdS-brane, the open rotating string ansatz is discussed. We construct the elliptic folded/circular open string solutions in the SU(2) and the SL(2) sectors, so that they satisfy the appropriate boundary conditions. On the other hand, in the SU(2) sector of the gauge theory, we compute the matrix of anomalous dimension of the defect operator, which turns out to be the hamiltonian of an open integrable spin chain. Then we consider the coordinate Bethe ansatz with arbitrary number of impurities, and compare the boundary condition of the Bethe wavefunction with that of the corresponding open string solution. We also discuss the Bethe ansatz for the open SL(2) spin chain with several supports from the string theory side. Then, in both SU(2) and SL(2) sectors, we analyze the Bethe equations in the thermodynamic limit and formulate the 'doubling trick' on the Riemann surface associated with the gauge theory.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2006/01/112
  DOI ID：10.1088/1126-6708/2006/01/112, ISSN：1029-8479, ORCID：48400343, arXiv ID：hep-th/0511139, Web of Science ID：WOS:000235034000112
• Classical integrability and super Yangian of superstring on AdS(5) x S-5　　　　　　　　　　　　　　　
  Machiko Hatsuda; Kentaroh Yoshida
  ADVANCES IN THEORETICAL AND MATHEMATICAL PHYSICS, 巻：9, 号：5, 開始ページ：703, 終了ページ：728, 2005年10月, ［査読有り］
  We discuss a classical integrability in the type IIB string theory on the AdS(5) x S-5 background. By using the Roiban - Siegel formulation of the superstring on the AdS(5) x S-5, we carefully treat the Wess - Zumino term and the constraint conditions intrinsic to the supersymmetric case and construct explicitly non-local charges for a hidden infinite-dimensional symmetry. The existence of the symmetry is shown by Bena - Polchinski - Roiban. Then the super Yangian algebra is calculated. We also show the Serre relation ensuring the structure of the Hopf algebra. In addition, the classical integrability is discussed by constructing the Lax pair and the transfer matrix.
  INT PRESS BOSTON, INC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.4310/ATMP.2005.v9.n5.a2
  DOI ID：10.4310/ATMP.2005.v9.n5.a2, ISSN：1095-0761, eISSN：1095-0753, ORCID：48400384, arXiv ID：hep-th/0407044, Web of Science ID：WOS:000240745000002
• Thermodynamic behavior of fuzzy membranes in pp-wave matrix model　　　　　　　　　　　　　　　
  H Shin; K Yoshida
  PHYSICS LETTERS B, 巻：627, 開始ページ：188, 終了ページ：196, 2005年10月, ［査読有り］
  We discuss a two-body interaction of membrane fuzzy spheres in a pp-wave matrix model at finite temperature by considering the system that a fuzzy sphere rotates with a constant radius r around the other one sitting at the origin in the SO(6) symmetric space. This system of two fuzzy spheres is supersymmetric at zero temperature and there is no interaction between them. Once the system is coupled to the heat bath, supersymmetries are completely broken and non-trivial interaction appears. We numerically show that the potential between fuzzy spheres is attractive and so the rotating fuzzy sphere tends to fall into the origin. The analytic formula of the free energy is also evaluated in the large N limit. It is well approximated by a polylog function. (c) 2005 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2005.09.007
  DOI ID：10.1016/j.physletb.2005.09.007, ISSN：0370-2693, eISSN：1873-2445, ORCID：48400333, arXiv ID：hep-th/0507029, Web of Science ID：WOS:000232955700025
• Integrability and higher loops in AdS/dCFT correspondence　　　　　　　　　　　　　　　
  Y Susaki; Y Takayama; K Yoshida
  PHYSICS LETTERS B, 巻：624, 号：1-2, 開始ページ：115, 終了ページ：124, 2005年09月, ［査読有り］
  We further study the correspondence between open semiclassical strings and long defect operators which is discussed in our previous work [Y. Susaki, Y. Takayama, K. Yoshida, hep-th/0410139]. We give an interpretation of the spontaneous symmetry breaking of SO(6) -> SO(3)(H) x SO(3)(V) from the viewpoint of the Riemann surface by following the argument of Minahan. Then we use the concrete form of the resolvent for a single cut solution and compute the anomalous dimension of operators dual to an open pulsating string at three-loop level. In the string side we obtain the energy of the open pulsating string solution by semiclassical analysis. Both results agree at two-loop level but we find a three-loop discrepancy. (c) 2005 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2005.07.058
  DOI ID：10.1016/j.physletb.2005.07.058, ISSN：0370-2693, eISSN：1873-2445, ORCID：48400334, arXiv ID：hep-th/0504209, Web of Science ID：WOS:000232071300012
• Bubbling 1/2 BPS geometries and Penrose limits　　　　　　　　　　　　　　　
  Y Takayama; K Yoshida
  PHYSICAL REVIEW D, 巻：72, 号：6, 開始ページ：066014, 2005年09月, ［査読有り］
  We discuss how to take a Penrose limit in bubbling 1/2 Bogomol'nyi-Prasad-Sommerfield geometries at the stage of a single function z(x(1),x(2),y). By starting from the z of the AdS(5)xS(5), we can directly derive that of the pp wave via the Penrose limit. In the course of the calculation, the function z for the pp wave with 1/R-2 corrections is obtained. We see that it surely reproduces the pp wave with 1/R-2 terms. We also investigate the pp wave with higher-order 1/R-2 corrections. In addition, the Penrose limit in the configuration of the concentric rings is considered.
  AMER PHYSICAL SOC, 英語
  DOI：https://doi.org/10.1103/PhysRevD.72.066014
  DOI ID：10.1103/PhysRevD.72.066014, ISSN：1550-7998, eISSN：1550-2368, ORCID：48400291, arXiv ID：hep-th/0503057, Web of Science ID：WOS:000232230100095
• Graviton and spherical graviton potentials in plane-wave matrix model: Overview and perspective
  Yoshida Kentaroh; Shin Hyeonjoon
  4th International Symposium on Quantum Theory and Symmetries and 6th International Workshop on Lie Theory and Its Applications in Physics, 2005年08月, ［査読有り］
  ORCID：48400392, arXiv ID：hep-th/0511187
• Discrete light-cone quantization in pp-wave background　　　　　　　　　　　　　　　
  K Uzawa; K Yoshida
  PHYSICS LETTERS B, 巻：619, 号：3-4, 開始ページ：333, 終了ページ：339, 2005年07月, ［査読有り］
  We discuss the discrete light-cone quantization (DLCQ) of a scalar field theory on the maximally supersymmetric pp-wave background in ten dimensions. It has been shown that the DLCQ can be carried out in the same way as in the two-dimensional Minkowski spacetime. Then, the vacuum energy is computed by evaluating the vacuum expectation value of the light-cone Hamiltonian. The results are consistent with the effective potential obtained in our previous work [hep-th/0402028]. (c) 2005 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.physletb.2005.06.018
  DOI ID：10.1016/j.physletb.2005.06.018, ISSN：0370-2693, eISSN：1873-2445, ORCID：48400393, arXiv ID：hep-th/0506061, Web of Science ID：WOS:000230373400018
• Open semiclassical strings and long defect operators in AdS/dCFT correspondence　　　　　　　　　　　　　　　
  Y Susaki; Y Takayama; K Yoshida
  PHYSICAL REVIEW D, 巻：71, 号：12, 開始ページ：126006, 2005年06月, ［査読有り］
  We consider defect composite operators in a defect superconformal field theory obtained by inserting an AdS(4)xS(2)-brane in the AdS(5)xS(5) background. The one-loop dilatation operator for the scalar sector is represented by an integrable open spin chain. We give a description to construct coherent states for the open spin chain. Then, by evaluating the expectation value of the Hamiltonian with the coherent states in a long operator limit, a Landau-Lifshitz type of sigma model action is obtained. This action is also derived from the string action and hence we find a complete agreement in both super Yang-Mills and string sides. We see that an SO(3)(H) pulsating string solution is included in the action and its energy completely agrees with the result calculated in a different method. In addition, we argue that our procedure would be applicable to other AdS-brane cases.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.71.126006
  DOI ID：10.1103/PhysRevD.71.126006, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400362, arXiv ID：hep-th/0410139, Web of Science ID：WOS:000230276100110
• Open M-branes on AdS(4/7) x S-7/4 revisited　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  NUCLEAR PHYSICS B, 巻：714, 号：1-2, 開始ページ：51, 終了ページ：66, 2005年05月, ［査読有り］
  We proceed-further with a study of an open supermembrane on the AdS(4/7) x S-7/4 backgrounds. An open supermembrane can have an X15-brane and a 9-brane as Dirichlet branes. In Ads and pp-wave cases the configurations of Dirichlet branes are restricted. A classification of possible Dirichlet branes, which is given up to and including the fourth order of a fermionic variable theta in hep-th/0310035, is shown to be valid even at full order of theta. We also discuss an open X15-brane on the AdS4/7 X S7/4 backgrounds. (c) 2005 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2005.02.031
  DOI ID：10.1016/j.nuclphysb.2005.02.031, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400387, arXiv ID：hep-th/0405109, Web of Science ID：WOS:000228712300003
• Membrane fuzzy sphere dynamics in plane-wave matrix model　　　　　　　　　　　　　　　
  H Shin; K Yoshida
  NUCLEAR PHYSICS B, 巻：709, 号：1-2, 開始ページ：69, 終了ページ：93, 2005年03月, ［査読有り］
  In plane-wave matrix model, the membrane fuzzy sphere extended in the SO(3) symmetric space is allowed to have periodic motion on a sub-plane in the SO(6) symmetric space. We consider a back.-round configuration composed of two such fuzzy spheres moving on the same sub-plane and the one-loop quantum corrections to it. The one-loop effective action describing the fuzzy sphere interaction is computed up to the sub-leading order in the limit that the mean distance r between two fuzzy spheres is very large. We show that the leading order interaction is of the 1/r(7) type and thus the membrane fuzzy spheres interpreted as giant gravitons really behave as gravitons. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.njclphysb.2004.12.007
  DOI ID：10.1016/j.njclphysb.2004.12.007, ISSN：0550-3213, ORCID：48400409, arXiv ID：hep-th/0409045, Web of Science ID：WOS:000227312200003
• Thermodynamics of fuzzy spheres in pp-wave matrix model　　　　　　　　　　　　　　　
  H Shin; K Yoshida
  NUCLEAR PHYSICS B, 巻：701, 号：1-2, 開始ページ：380, 終了ページ：394, 2004年11月, ［査読有り］
  We discuss thermodynamics of fuzzy spheres in a matrix model on a pp-wave background. The exact free energy in the fuzzy sphere vacuum is computed in the mu --> infinity limit for an arbitrary matrix size N. The trivial vacuum dominates the fuzzy sphere vacuum at low temperature while the fuzzy sphere vacuum is more stable than the trivial vacuum at sufficiently high temperature. Our result supports that the fluctuations around the trivial vacuum would condense to form an irreducible fuzzy sphere above a certain temperature. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2004.09.002
  DOI ID：10.1016/j.nuclphysb.2004.09.002, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400375, arXiv ID：hep-th/0401014, Web of Science ID：WOS:000225023400013
• D-branes of covariant AdS superstrings: An Overview
  Sakaguchi Makoto; Yoshida Kentaroh
  12th International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 04), 開始ページ：907, 2004年08月, ［査読有り］
  We briefly review a covariant analysis of D-branes of type IIB superstring on
  the AdS_5xS^5 background from the \kappa-invariance of the Green-Schwarz string
  action. The possible configurations of D-branes preserving half of
  supersymmetries are classified in both cases of AdS_5xS^5 and the pp-wave
  background.
  ORCID：48400360, arXiv ID：hep-th/0408208
• Notes on D-branes of type IIB string on AdS(5) x S-5　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  PHYSICS LETTERS B, 巻：591, 号：3-4, 開始ページ：318, 終了ページ：324, 2004年07月, ［査読有り］
  We promote a study of D-branes of type IIB string on the AdS(5) x S-5 background. The possible D-branes preserving half of supersymmetries were classified up to and including the fourth order of fermionic variable theta in our previous work [hepth/0310228]. In this work we show that our classification is still valid even at the full order of theta. This proof supplements our previous results and completes the classification of D-branes in the type IIB string theory on the AdS(5) x S-5. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.physletb.2004.04.034
  DOI ID：10.1016/j.physletb.2004.04.034, ISSN：0370-2693, ORCID：48400388, arXiv ID：hep-th/0403243, Web of Science ID：WOS:000222194100016
• Effective potential in pp-wave geometry　　　　　　　　　　　　　　　
  K Uzawa; K Yoshida
  NUCLEAR PHYSICS B, 巻：683, 号：1-2, 開始ページ：122, 終了ページ：136, 2004年04月, ［査読有り］
  We calculate effective potentials in scalar field theories on the maximally supersymmetric pp-wave background in ten dimensions. For this purpose we have to work in the light-cone formulation, and hence we introduce two methods to compute them in the light-cone frame. One is to use the Yan's formula for evaluating one-loop correction terms. The other is to introduce a cut-off for the light-cone momentum. These methods are also confirmed in the case of Minkowski spacetime. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2004.02.002
  DOI ID：10.1016/j.nuclphysb.2004.02.002, ISSN：0550-3213, ORCID：48400352, arXiv ID：hep-th/0402028, Web of Science ID：WOS:000220465400006
• D-branes of covariant AdS superstrings　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  NUCLEAR PHYSICS B, 巻：684, 号：1-2, 開始ページ：100, 終了ページ：124, 2004年04月, ［査読有り］
  We consider D-branes of open superstrings in the AdS(5) x S-5 background. The possible configurations of D-branes preserving half of supersymmetries are classified by analyzing the kappa-invariance of an open superstring in a covariant manner. We also revisit the classification of D-branes in the pp-wave background. It is shown that Penrose limits of the possible D-branes in the AdS(5) x S-5 dive all of the D-branes in the pp-wave. In addition, a 1/4 supersymmetric, D-string, which is related to the D-string preserving 8 dynamical supersymmetries in the pp-wave, is presented. We also discuss the relation between our result and the Ads branes in a brane probe analysis. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2004.02.016
  DOI ID：10.1016/j.nuclphysb.2004.02.016, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400296, arXiv ID：hep-th/0310228, Web of Science ID：WOS:000220722600003
• Dirichlet branes of the covariant open supermembrane in AdS(4) x S-7 and AdS(7) x S-4　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  NUCLEAR PHYSICS B, 巻：681, 号：1-2, 開始ページ：137, 終了ページ：151, 2004年03月, ［査読有り］
  We discuss an open supermembrane theory in the AdS(4) x S-7 and AdS(7) x S-4 backgrounds. The possible Dirichlet branes of an open supermembrane are classified by analyzing the covariant Wess-Zumino term. All of the allowed configurations are related to those on the pp-wave background via the Penrose limit. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2004.01.008
  DOI ID：10.1016/j.nuclphysb.2004.01.008, ISSN：0550-3213, ORCID：48400386, arXiv ID：hep-th/0310035, Web of Science ID：WOS:000220012400006
• One-loop flatness of membrane fuzzy sphere interaction in plane-wave matrix model　　　　　　　　　　　　　　　
  H Shin; K Yoshida
  NUCLEAR PHYSICS B, 巻：679, 号：1-2, 開始ページ：99, 終了ページ：126, 2004年02月, ［査読有り］
  In the plane-wave matrix model, the background configuration of two membrane fuzzy spheres, one of which rotates around the other one in the SO(6) symmetric space, is allowed as a classical solution. We study the one-loop quantum corrections to this background in the path integral formulation. Firstly, we show that each fuzzy sphere is stable under the quantum correction. Secondly, the effective potential describing the interaction between fuzzy spheres is obtained as a function of r, which is the distance between two fuzzy spheres. It is shown that the effective potential is flat and hence the fuzzy spheres do not feel any force. The possibility on the existence of flat directions is discussed. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.nuclphysb.2003.12.003
  DOI ID：10.1016/j.nuclphysb.2003.12.003, ISSN：0550-3213, ORCID：48400391, arXiv ID：hep-th/0309258, Web of Science ID：WOS:000188702700003
• Dirichlet branes of the covariant open supermembrane on a pp-wave background　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  NUCLEAR PHYSICS B, 巻：676, 号：1-2, 開始ページ：311, 終了ページ：324, 2004年01月, ［査読有り］
  We discuss an open supermembrane theory on the maximally supersymmetric pp-wave background in eleven dimensions. The boundary surfaces of an open supermembrane are studied by using the covariant supermembrane theory. In particular, we find the configurations of M5-branes and 9-branes preserving a half of supersymmetries at the origin. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2003.10.024
  DOI ID：10.1016/j.nuclphysb.2003.10.024, ISSN：0550-3213, ORCID：48400371, arXiv ID：hep-th/0306213, Web of Science ID：WOS:000187738100011
• Spectrum of eleven-dimensional supergravity on a pp-wave background　　　　　　　　　　　　　　　
  T Kimura; K Yoshida
  PHYSICAL REVIEW D, 巻：68, 号：12, 開始ページ：125007, 2003年12月, ［査読有り］
  We calculate the spectrum of the linearized supergravity around the maximally supersymmetric pp-wave background in eleven dimensions. The resulting spectrum agrees with that of zero-mode Hamiltonian of a supermembrane theory on the pp-wave background. We also discuss the connection with the Kaluza-Klein zero modes of an AdS(4)xS(7) background.
  AMER PHYSICAL SOC, 英語
  DOI：https://doi.org/10.1103/PhysRevD.68.125007
  DOI ID：10.1103/PhysRevD.68.125007, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400310, arXiv ID：hep-th/0307193, Web of Science ID：WOS:000187969200062
• M-theory on a time-dependent plane-wave　　　　　　　　　　　　　　　
  M Sakaguchi; K Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：11, 号：11, 開始ページ：030, 2003年11月, ［査読有り］
  We propose a matrix model on a homogeneous plane-wave background with 20 supersymmetries. This background is anti-Mach type and is related to the time-dependent plane-wave background. We study supersymmetries of this matrix model. The vacuum energy of the abelian part is also calculated. In addition we find classical solutions such as graviton solution, fuzzy sphere and hyperboloid.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2003/11/030
  DOI ID：10.1088/1126-6708/2003/11/030, ISSN：1029-8479, ORCID：48400389, arXiv ID：hep-th/0309025, Web of Science ID：WOS:000188765300030
• Partition function and open/closed string duality in type IIA string theory on a pp-wave　　　　　　　　　　　　　　　
  H Shin; K Sugiyama; K Yoshida
  NUCLEAR PHYSICS B, 巻：669, 号：1-2, 開始ページ：78, 終了ページ：102, 2003年10月, ［査読有り］
  We discuss partition functions of N = (4,4) type IIA string theory on the pp-wave background. This theory is shown to be modular invariant. The boundary states are constructed and possible D-brane instantons are classified. Then we calculate cylinder amplitudes in both closed and open string descriptions and check the open/closed string duality. Furthermore we consider general properties of modular invariant partition functions in the case of pp-waves. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語
  DOI：https://doi.org/10.1016/j.nuclphysb.2003.07.015
  DOI ID：10.1016/j.nuclphysb.2003.07.015, ISSN：0550-3213, eISSN：1873-1562, ORCID：48400279, arXiv ID：hep-th/0306087, Web of Science ID：WOS:000185587500003
• Ground state of the supermembrane on a pp wave　　　　　　　　　　　　　　　
  N Nakayama; K Sugiyama; K Yoshida
  PHYSICAL REVIEW D, 巻：68, 号：2, 開始ページ：026001, 2003年07月, ［査読有り］
  We consider the ground state of a supermembrane on the maximally supersymmetric pp-wave background by using the quantum-mechanical procedure of de Wit, Hoppe, and Nicolai. On the pp-wave background the ground state has a nontrivial structure even in the zero-mode Hamiltonian. The supergravity multiplet in flat space comes to split with a certain energy difference. We explicitly derive the supersymmetric ground-state wave function for the zero-mode Hamiltonian, which is obviously normalizable. Moreover, we discuss the nonzero-mode Hamiltonian and construct an example of the ground-state wave function with the truncation of variables, whose L-2 norm can be represented by an asymptotic series.
  AMERICAN PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.68.026001
  DOI ID：10.1103/PhysRevD.68.026001, ISSN：0556-2821, ORCID：48400323, arXiv ID：hep-th/0209081, Web of Science ID：WOS:000185229300092
• Type IIA string and matrix string on pp-wave　　　　　　　　　　　　　　　
  K Sugiyama; K Yoshida
  NUCLEAR PHYSICS B, 巻：644, 号：1-2, 開始ページ：128, 終了ページ：150, 2002年11月, ［査読有り］
  We study type IIA string theories on the pp-waves with 24 supercharges. The type IIA pp-wave backgrounds are derived from the maximally supersymmetric pp-wave solution in eleven dimensions through the toroidal compactification on the spatial isometry directions. The associated actions of type IIA strings are obtained by using these metrics and other background fields of the type IIA supergravities on the one hand. On the other hand, we derive these theories from D = 11 supermembrane on the pp-wave via double-dimensional reduction for the spatial isometry directions. The resulting actions agree with those of type IIA strings obtained in the study of the supergravities. Also, the action of the matrix string is written down. Moreover, the quantization of closed and open strings is discussed. In particular, we study Dp-branes allowed in one of the type IIA theories. (C) 2002 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S0550-3213(02)00820-9
  DOI ID：10.1016/S0550-3213(02)00820-9, ISSN：0550-3213, ORCID：48400394, arXiv ID：hep-th/0208029, Web of Science ID：WOS:000179095800007
• Supermembrane on the pp-wave background　　　　　　　　　　　　　　　
  K Sugiyama; K Yoshida
  NUCLEAR PHYSICS B, 巻：644, 号：1-2, 開始ページ：113, 終了ページ：127, 2002年11月, ［査読有り］
  We study the closed and open supermembranes on the maximally supersymmetric pp-wave background. In the framework of the membrane theory, the superalgebra is calculated by using the Dirac bracket and we obtain its central extension by surface terms. The result supports the existence of the extended objects in the membrane theory in the pp-wave limit. When the central terms are discarded, the associated algebra completely agrees with that of Berenstein-Maldacena-Nastase matrix model. We also discuss the open supermembranes on the pp-wave and elaborate the possible boundary conditions. (C) 2002 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S0550-3213(02)00794-0
  DOI ID：10.1016/S0550-3213(02)00794-0, ISSN：0550-3213, ORCID：48400353, arXiv ID：hep-th/0206070, Web of Science ID：WOS:000179095800006
• Giant graviton and quantum stability in the matrix model on a pp-wave background　　　　　　　　　　　　　　　
  K Sugiyama; K Yoshida
  PHYSICAL REVIEW D, 巻：66, 号：8, 開始ページ：085022, 2002年10月, ［査読有り］
  We study classical solutions in the Berenstein-Maldacena-Nastase matrix model. A supersymmetric (1/2 Bogomol'nyi-Prasad-Sommerfield) fuzzy sphere is one of the classical solutions and corresponds to a giant graviton. We also consider other classical solutions, such as a nonsupersymmetric fuzzy sphere and harmonic oscillating gravitons. Some properties of oscillating gravitons are discussed. In particular, oscillating gravitons turn into the usual supergravitons in the limit mu-->0. Moreover, we calculate the one-loop effective action around the supersymmetric fuzzy sphere by the use of the background field method and show the quantum stability of the giant graviton. Also, the instability of the nonsupersymmetric fuzzy sphere is proven.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.66.085022
  DOI ID：10.1103/PhysRevD.66.085022, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400364, arXiv ID：hep-th/0207190, Web of Science ID：WOS:000179081500074
• BPS conditions of supermembrane on the pp-wave　　　　　　　　　　　　　　　
  K Sugiyama; K Yoshida
  PHYSICS LETTERS B, 巻：546, 号：1-2, 開始ページ：143, 終了ページ：152, 2002年10月, ［査読有り］
  We study the BPS conditions in the closed supermembranes on the maximally supersymmetric pp-wave background. In particular, the 1/2 and 1/4 BPS states are discussed in detail. Moreover, we comment on the zero-modes in the invariant mass formulae of the theory. (C) 2002 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S0370-2693(02)02669-2
  DOI ID：10.1016/S0370-2693(02)02669-2, ISSN：0370-2693, ORCID：48400341, arXiv ID：hep-th/0206132, Web of Science ID：WOS:000178923400018
• Phase structure of compact QED from the sine-Gordon / massive Thirring duality
  Yoshida, Kentaroh
  2002年04月, ［査読有り］
  We discuss a phase structure of compact QED in four dimensions by considering
  the theory as a perturbed topological model. In this scenario we use the
  singular configuration with an appropriate regularization, and so obtain the
  results similar to the lattice gauge theory due to the effect of topological
  objects. In this paper we calculate the thermal pressure of the topological
  model by the use of a one-dimensional Coulomb gas approximation, which leads to
  a phase structure of full compact QED. Furthermore the critical-line equation
  is explicitly evaluated. We also discuss relations between the monopole
  condensation in compact QED in four dimensions and the chiral symmetry
  restoration in the massive Thirring model in two dimensions.
  研究論文（学術雑誌）
  ORCID：48400342, arXiv ID：hep-th/0204086
• Phase structure of a compact U(1) gauge theory from the viewpoint of a sine-Gordon model　　　　　　　　　　　　　　　
  K Yoshida; W Souma
  PHYSICAL REVIEW D, 巻：64, 号：12, 開始ページ：125002, 2001年12月, ［査読有り］
  We discuss the phase structure of the four-dimensional compact U(1) gauge theory at finite temperature using a deformation of the topological model, Its phase structure can be determined by the behavior of the Coulomb gas (CG) system on the cylinder. We utilize the relation between the CG system and the sine-Gordon (SG) model, and investigate the phase structure of the gauge theory in terms of the SG model. Especially, the critical-line equation of the gauge theory in the strong-coupling and high-temperature region is obtained by calculating the one-loop effective potential of the SG model.
  AMER PHYSICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1103/PhysRevD.64.125002
  DOI ID：10.1103/PhysRevD.64.125002, ISSN：2470-0010, eISSN：2470-0029, ORCID：48400379, arXiv ID：hep-th/0103075, Web of Science ID：WOS:000172867100066
• Confining phases of a compact U(1) gauge theory from the sine-Gordon / massive Thirring duality
  Yoshida, Kentaroh
  2001年10月, ［査読有り］
  We consider the phase structure of a pure compact U(1) gauge theory in four
  dimensions at finite temperature by treating this system as a perturbative
  deformation of the topological model. Phases of a gauge theory can be
  investigated from the phase structure of the topological model. The thermal
  pressure of the topological model has been calculated, from which its phase
  structure can be derived. We have obtained phases of a compact U(1) gauge
  theory. Moreover, the critical-line equation has been explicitly evaluated.
  研究論文（学術雑誌）
  ORCID：48400410, arXiv ID：hep-th/0110153
• Deconfining phase transition in QCD(4) and QED(4) at finite temperature　　　　　　　　　　　　　　　
  K Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：04, 号：4, 開始ページ：030, 2001年04月, ［査読有り］
  We investigate the deconfining phase transition in QCD(4) and QED(4) at finite temperature using a perturbative deformation of topological quantum field theory (TQFT). A modified maximal abelian gauge (MAG) is utilized in the analysis. In this case, we can derive the linear potential studying the 2D theory through Parisi-Sourlas (PS) dimensional reduction. The mechanism of deconfining phase transition is proposed. It is geometrical to discuss the thermal effect on the linear potential. All we have to do is to investigate the behavior of topological objects as such instantons and vortices on a cylinder. This is the great advantage of our scenario. This mechanism is also applied in the case of QED4. The phase structure at the high temperature of QED is investigated using the Coulomb potential on a cylinder. It coincides with the result in the lattice compact U(1) gauge theory. Also, QCD with MAG has the property called the abelian dominance, which enables us to discuss the deconfinement of QCD(4).
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2001/04/030
  DOI ID：10.1088/1126-6708/2001/04/030, ISSN：1029-8479, ORCID：48400331, arXiv ID：hep-th/0012237, Web of Science ID：WOS:000169386600030
• The effect of the boundary conditions in the reformulation of QCD(4)　　　　　　　　　　　　　　　
  K Yoshida
  JOURNAL OF HIGH ENERGY PHYSICS, 巻：07, 号：7, 開始ページ：007, 2000年07月, ［査読有り］
  We discuss the phase structure of QCD(4) as a perturbative deformation of the Topological Quantum Field Theory (TQFT). When we choose a special maximal abelian gauge (MAG) as the gauge fixing, the TQFT sector is equivalent to a 2D O(3) non-linear sigma model (NLSM). We consider the finite temperature case, and investigate the effect of the boundary conditions and the phase structure of the TQFT sector. It can have a deconfining phase under the twisted boundary conditions. However, this phase is screened once pertubative parts are added. We conclude that the information about the phase structure is encoded in the U(1) background in the case of the MAG.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1088/1126-6708/2000/07/007
  DOI ID：10.1088/1126-6708/2000/07/007, ISSN：1029-8479, ORCID：48400336, arXiv ID：hep-th/0004184, Web of Science ID：WOS:000168153900007

• カオスと超弦理論　　　　　　　　　　　　　　　
  吉田健太郎
  パリティ, 号：1月, 2017年01月, ［査読有り］, ［招待有り］
  記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）
• なぜ物理学者のなったのか？　　　　　　　　　　　　　　　
  吉田健太郎
  パリティ, 号：10月, 2014年10月, ［査読有り］, ［招待有り］

• 2次元非線形シグマ模型のヤン・バクスター変形　　　　　　　　　　　　　　　
  吉田 健太郎, ［単著］
  Springer, 2021年
  ISBN：9789811617034

• AdS_5 × S^5上の超弦理論のYang-Baxter変形と一般化された超重力理論　　　　　　　　　　　　　　　
  吉田健太郎
  日本物理学会2025年春季大会, 2025年03月, ［招待有り］
  2025年03月 - 2025年03月, 日本語, 口頭発表（招待・特別）
• 補助場を含む4次元チャーン・サイモンズ理論　　　　　　　　　　　　　　　
  吉田健太郎
  NITEP 理論物理学セミナーシリーズ, 2024年12月, ［招待有り］
  2024年12月 - 2024年12月, 英語, 公開講演，セミナー，チュートリアル，講習，講義等
• 補助場を含む4次元チャーン・サイモンズ理論　　　　　　　　　　　　　　　
  吉田健太郎
  2024 East Asia Joint Workshop on Fields and Strings, 2024年11月, ［招待有り］
  2024年11月 - 2024年11月, 英語, 口頭発表（招待・特別）
• 補助場を含む4次元チャーン・サイモンズ理論　　　　　　　　　　　　　　　
  吉田健太郎
  2024 NTU-Kanto Joint High Energy Physics Workshop, 2024年11月, ［招待有り］
  2024年11月 - 2024年11月, 英語, 口頭発表（招待・特別）
• 補助場を含む4次元チャーン・サイモンズ理論　　　　　　　　　　　　　　　
  吉田健太郎
  日本大学理工学部素粒子論研究室コロキウム, 2024年11月, ［招待有り］
  2024年11月 - 2024年11月, 日本語, 公開講演，セミナー，チュートリアル，講習，講義等
• 補助場を入れた4次元Chern-Simons理論の拡張　　　　　　　　　　　　　　　
  吉田健太郎
  茨大-東工大合宿, 2024年10月, ［招待有り］
  2024年10月 - 2024年10月, 日本語, 口頭発表（招待・特別）
• AdS/CFTへの誘い　　　　　　　　　　　　　　　
  吉田健太郎
  バナラス・ヒンドゥ大学における一般向け講演, 2016年11月, ［招待有り］
  2016年11月 - 2016年11月, 英語, 公開講演，セミナー，チュートリアル，講習，講義等

• 量子力学演習, 京都大学

• 日本物理学会

• 量子・重力と機械学習　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 学術変革領域研究(A), 学術変革領域研究(A), 2022年06月16日 - 2027年03月31日
  橋本 幸士; 吉田 健太郎; 杉下 宗太郎; 村田 仁樹, 京都大学
  配分額（総額）：117910000, 配分額（直接経費）：90700000, 配分額（間接経費）：27210000
  課題番号：22H05115
• ホログラフィー原理の成立限界：時空再構成手法の統合による重力双対有無判定法の確立　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(B), 2022年04月01日 - 2025年03月31日
  橋本 幸士; 村田 佳樹; 吉田 健太郎, 京都大学
  配分額（総額）：16900000, 配分額（直接経費）：13000000, 配分額（間接経費）：3900000
  課題番号：22H01217
• 量子重力と自然性‐弦理論から見たプランクスケールと電弱スケールの統合　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2020年04月01日 - 2024年03月31日
  川合 光; 吉田 健太郎, 京都大学
  配分額（総額）：4030000, 配分額（直接経費）：3100000, 配分額（間接経費）：930000
  「標準模型は本当に弦理論の真空か」という問いは、現在の素粒子論にとって最も重要な問題であるといっても過言ではない。これは弦理論の現実性がクローズアップされた、1980年代の中ごろからの大問題であるが、いまだに明確な答えは得られていない。一方、この十年の実験や観測の結果は、低エネルギーからのボトムアップ的なアプローチと、プランクスケールからのトップダウン的なアプローチが大変近いものであることを示している。いいかえると、電弱スケールとプランクスケールの間にある「小さなギャップ」を埋めることで、両者がつながる可能性がある。この「小さなギャップ」としては、暗黒物質、バリオン数生成、宇宙初期のインフレーションなど、場の理論内で解決できるものに加えて、量子重力・自然性問題など、場の理論の考え方自体の変更も考慮する必要がある。
  当研究者は長年、“行列模型による時空と物質の創発”と、“自然性に対する新しい理解の試み”の２つの視野を融合させることを考えている。2021年度は、以下のような問題を有機的に結び付けて、上記の「小さなギャップ」の全体像の解明を試みた。
  ⅰ）Higgs場の質量および自己結合定数の起源をプランクスケールの物理から解明する。また、その観点からHiggsインフレーションを調べ、プランクスケールに近いエネルギー領域の解明を目指す。
  ⅱ）弦理論・行列模型から帰結されるマルティバースを解析し、低エネルギー有効理論としての場の量子論がどのように修正されるべきかを議論し、自然性問題の解明を目指す。
  ⅲ）ブラックホールの時間発展を形成から蒸発まで、場の理論の第１原理から解析し、重力の量子論と古典論の本質的な違いを解明する。
  課題番号：20K03970
• 超弦理論から創発される一般化された超重力理論におけるD-ブレインとブラックホール　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 基盤研究(B), 基盤研究(B), 2018年04月01日 - 2022年03月31日
  吉田 健太郎; 綿村 哲; 村田 佳樹; 大河内 豊; 酒谷 雄峰; 橋本 幸士; 吉岡 興一, 京都大学
  配分額（総額）：17030000, 配分額（直接経費）：13100000, 配分額（間接経費）：3930000
  近年、2次元の場の量子論において、TTbar変形と呼ばれるirrelevantな変形が精力的に研究されている。このTTbar変形はTTbar演算子と呼ばれるエネルギー・運動量テンソルの行列式で定義される演算子によって引き起こされる。この演算子は複合演算子としてwell-definedであり、そのエネルギー固有状態での期待値は因子化と呼ばれる特別な性質を示すことが、2004年にAlexander Zamolodchikovによって示された。その後、2016年になって、このTTbar演算子によって引き起こされる理論空間におけるフローが盛んに研究されるようになった。irrelevantな変形にもかかわらず、制御が可能であり、古典的には質量ゼロの自由スカラー場のTTbar変形が弦の南部-後藤作用になることからも、量子重力理論への手がかりを与える重要な研究課題と考えられている。
  春名、石井、川合、酒井との共同研究によって、2次元O(N)ベクトル模型を具体例にとり、この性質のよいTTbar変形においても、非ノルムを持った非物理的な状態が含まれることをラージN極限において示した。この結果は、量子論的に整合的な理論を得るためには、TTbar変形だけではダメで、さらに付加的なチューニングを要することを意味している。また、奥村氏との共同研究により、TTbar変形と2次元Liouville重力理論の関係を議論した。
  別の研究課題として、坂本、福島と共同研究をおこない、4次元チャーン・サイモンズ理論と2次元の可積分な非線形シグマ模型およびそのヤン・バクスター変形の関係を議論した。特に、4次元のチャーン・サイモンズ理論から、AdS5xS5上の超弦理論のhomogeneousなヤン・バクスター変形を導出することができた。
  課題番号：18H01214
• ゲージ理論と重力理論の双対性における基礎的な機構の研究　　　　　　　　　　　　　　　
  京都大学, 研究大学強化促進事業 学際・国際・人際融合事業「知の越境」 融合チーム研究プログラム – SPIRITS –, 2019年04月 - 2021年03月
  吉田健太郎, 京都大学, 研究代表者
  配分額（総額）：6690000
  競争的資金
• 超弦理論における時空の可積分構造とカオス　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 基盤研究(C), 基盤研究(C), 2015年04月01日 - 2019年03月31日
  吉田 健太郎; 松本 拓也; 橋本 幸士; 亀山 尚史; 川井 大輔, 京都大学
  配分額（総額）：4030000, 配分額（直接経費）：3100000, 配分額（間接経費）：930000
  弦理論において、弦は様々な時空の上を運動することができる。よって、いろいろな弦の古典的な運動を考えることが可能であり、その運動は時空によっては可積分である場合もあれば、非可積分であってカオス的、あるいは乱流的な振る舞いを示すこともある。本研究課題では弦の古典的な運動に着目し、可積分性・非可積分性の観点から時空の構造について研究を行い、Yang-Baxter変形と呼ばれる系統的な手法について確立した。
  課題番号：15K05051
• 超弦理論から創発される新しい低エネルギー有効理論　　　　　　　　　　　　　　　
  京都大学, 研究大学強化促進事業 学際・国際・人際融合事業「知の越境」 融合チーム研究プログラム – SPIRITS –, 2017年04月 - 2019年03月
  吉田健太郎, 京都大学, 研究代表者
  配分額（総額）：8340000
  競争的資金
• カオスと超弦理論による場の量子論の選別　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 挑戦的萌芽研究, 挑戦的萌芽研究, 2015年04月01日 - 2018年03月31日
  橋本 幸士; 吉田 健太郎; 佐々 真一, 大阪大学
  配分額（総額）：3770000, 配分額（直接経費）：2900000, 配分額（間接経費）：870000
  QCDの低エネルギー有効作用である線形シグマ模型においてカオス解析を行い、QCD相転移のエネルギースケールでカオスが発生していることを発見した。これは、QCDという量子性が強い場の量子論において、カイラル凝縮というゲージ不変演算子の真空期待値の時間依存性に、カオスが現れることを解析できることを示している。また、ホログラフィー原理を用いることにより、超対称性を持つQCDにおいて同様の解析を行うことができ、その結果、カオスを示すリャプノフ指数が計算された。このリャプノフ指数は、ゲージ群SU(N)のNが大きくなればなるほど小さくなるというスケーリング則を満たしており、カオスの減少が発見された。
  課題番号：15K13483
• 超弦理論における時空の可積分構造とカオス　　　　　　　　　　　　　　　
  京都大学, 研究大学強化促進事業 学際・国際・人際融合事業「知の越境」 融合チーム研究プログラム – SPIRITS –, 2015年04月 - 2017年03月
  吉田健太郎, 京都大学, 研究代表者
  配分額（総額）：4100000
  競争的資金
• 超弦理論を用いたブラックホールエントロピーの微視的研究　　　　　　　　　　　　　　　
  京都大学, 京都大学グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」, GCOE境界領域推進プロジェクト, 2011年04月 - 2012年03月
  吉田健太郎, 京都大学, 研究代表者
  配分額（総額）：274780
  競争的資金
• ゲージ・重力対応における非相対論的極限の研究　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 若手研究(B), 若手研究(B), 2010年 - 2012年
  吉田 健太郎, 京都大学
  配分額（総額）：4160000, 配分額（直接経費）：3200000, 配分額（間接経費）：960000
  本研究課題の目的は、ゲージ・重力対応における非相対論的極限に関する研究を進めることであった。まず、非相対論的な理論に双対であると考えられる時空を標的空間にもつ弦理論の可積分構造について深い理解を得ることができた。特に、量子アフィン代数の表現の構成、ヤンギアン代数との関係を明らかにした。また、非相対論的な共形対称性に関する研究をおこない、無限次元拡大や超対称性を含める拡張について議論した。
  課題番号：22740160
• 超対称ゲージ理論の真空構造と可積分模型の対応関係　　　　　　　　　　　　　　　
  京都大学, 京都大学グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」, GCOE境界領域推進プロジェクト, 2010年04月 - 2011年03月
  吉田健太郎; 吉岡興一, 京都大学, 研究代表者
  配分額（総額）：556800
  競争的資金
• ゲージ/重力対応における非相対論的極限の研究　　　　　　　　　　　　　　　
  京都大学, 京都大学グローバルCOEプログラム「普遍性と創発性から紡ぐ次世代物理学」, GCOE研究基盤強化プロジェクト, 2009年04月 - 2010年03月
  吉田健太郎; 吉岡興一, 京都大学, 研究代表者
  配分額（総額）：470000
  競争的資金
• PP波背景上の超膜理論と行列模型　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, 2004年 - 2006年
  吉田 健太郎, 大学共同利用機関法人高エネルギー加速器研究機構
  配分額（総額）：3400000, 配分額（直接経費）：3400000
  前年度の研究に引き続き、PP波背景上の行列模型における重力子解の構成、およびその間の重力ポテンシャルの計算をいった。今回行ったのは、前年度の球面状の重力子解とは異なる点状の重力子解の構成である。これに対しても、行列模型において同様なポテンシャルの計算が可能であり、結果として1/r^7の振る舞いをすることを示した。
  この結果は、ゲージ/重力対応を強く示唆する興味深い結果である。
  また、PP波背景上の行列模型を有限温度系に拡張し、自由エネルギーの考察をし、真空の安定性を調べた。ゼロ温度では超対称性のため二つの真空が縮退しているが、有限温度ではこの対称性が破れて縮退が解けるため、どちらの真空がより安定かを調べることは、M理論の真空を理解する上で非常に興味深い。すべての温度領域で解析的な計算を実行するのは困難であるため、モンテカルロシミュレーションを用いた解析を行い、二つの真空の自由エネルギーの大きさを比較した。その結果、高温領域ではtransverse M5-brane真空と呼ばれる真空が最も安定であること、中間温度領域に非可換球面真空が安定化する非常にせまい領域があること、がわかった。
  課題番号：04J03778

• 超弦理論とはなにか？　　　　　　　　　　　　　　　
  パネリスト
  京都大学, アカデミックディ2016, 2016年09月18日 - 2016年09月18日

• 物質の究極の構成要素　　　　　　　　　　　　　　　
  本人, 埼玉新聞, 2024年04月24日, ［新聞・雑誌］