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最近のセミナー (Recent Seminars)

Deformation of N=4 SYM with space-time dependent couplings

When:2018/02/09 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Jose J. Fernandez-Melgarejo (YITP)
Abstract:We will firstly study deformations of N=4 supersymmetric Yang-Mills theory with couplings and masses depending on space-time. The conditions to preserve part of the supersymmetry are derived and a lot of solutions of these conditions are found. The main example is the case with ISO(1,1)×SO(3)×SO(3) symmetry, in which couplings, as well as masses and the theta parameter, can depend on two spatial coordinates. When this case is enhanced to ISO(1,2), we obtain the Janus configuration found by Gaiotto&Witten. Secondly, we will study some of these solutions by embedding probe D3-branes in supergravity backgrounds with non-trivial fluxes. The effective action on the world-volume of the D3-branes is analyzed and a map between the deformation parameters and the fluxes is obtained. Based on
[arXiv:1710.09792] and [arXiv:1801.09394]
Reference:arXiv:1710.09792, arXiv:1801.09394

Very Special Conformal Field Theories and Holographic duals

When:2018/01/26 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Yu Nakayama (Rikkyo Univ.)
Abstract:Sometime ago Cohen and Glashow introduced the notion of Very Special
Relativity, which are subgroups of the Poincare group that preserve
one particular null direction. The realization of very special
relativity in field theories is a challenging question. Cohen and
Gashow even claimed that it is impossible without violating locality.
Their argument is based on the spurion analysis, but in this talk, I
show there is a loophole in their argument and I present some concrete
examples of field theory realization based on the idea of topological
twist. I also show new solutions of Einstein equation with matter,
motivated from the holographic realization of very special conformal
field theories.
Reference:arXiv:1707.05423.

Exotic five-branes of codimension two in heterotic supergravity

When:2018/01/17 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Shin Sasaki (Kitasato Univ.)
Abstract:In this talk, I introduce three (symmetric, neutral, gauge) distinct types of five-branes of codimension two in heterotic supergravity. We study T-duality chains of the five-branes where the famous Buscher rule receives string $\alpha’$-corrections. We explicitly write down the exotic $5^2_2$-brane solutions associated with the symmetric and the neutral types of the NS5-brane. The $O(2,2)$ monodromy structures of the $5^2_2$-brane solutions are investigated by the $\alpha’$-corrected generalized metric. Our analysis shows that the symmetric $5^2_2$-brane solution, which satisfies the standard embedding condition, is a T-fold and it exhibits a non-geometric nature. We also find that the neutral $5^2_2$-brane solution is a T-fold at least at $\mathcal{O}(\alpha’)$. By the Nahm construction of periodic monopoles, we work out the explicit solution of the gauge-type five-brane of codimension two. The $5^2_2$-brane of the gauge-type is shown to be geometric and not a T-fold.
Reference:arXiv:1608.01436, arXiv:1708.08066.

Flow equation, conformal symmetry, AdS geometries with general conformally flat boundary

When:2017/12/22 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Shuichi Yokoyama (YITP)
Abstract:In this talk I will speak about my recent works with S.Aoki on the study of mechanism of emergence of AdS geometry from CFT via flow equation.
A flow equation is a kind of operator renormalization which resolves UV singularity.
While this was used to help numerical simulation in lattice QCD, there has recently been a proposal to construct a one higher dimensional geometry associated with the flow equation in a QFT.
In our recent papers, I investigated aspects of an induced metric with the collaborator and our main results are the following.
i) Generally an induced metric becomes a quantum information metric called the Bures or Helstrom metric.
ii) For any CFT, induced metrics explicitly computed match (Poincare) AdS.
iii) Conformal symmetry of CFT converts to the AdS isometry after quantum averaging. This guarantees the emergence of AdS without explicit calculation.
iv) We generalize ii) and iii) in the case of any CFT defined on a general conformally flat manifold.
Reference:arXiv:1707.03982, arXiv:1709.07281

M2- and M5-branes in E_11 Current Algebra Formulation of M-theory

When:2017/12/08 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Shotaro Shiba (KEK)
Abstract:M-theory may be described in terms of E_11 algebra: All the degrees of freedom, including fields, coordinates and even M-branes, can be elements of E_11 group. Then we propose that equations of motion for M-branes are written down in E_11 algebra, using the current algebra formulation known as Sugawara construction. We also discuss the geometric equations, and show that there are static solutions when M2- or M5-brane exists alone and when M5-brane wraps around M2-brane. The latter situation can be realized because our geometric equation has a deviation from Einstein equation, thus avoiding the usual intersection rule of branes.
Reference:P. C. West, Phys. Lett. B 575, 333 (2003) [hep-th/0307098].
H. Sugawara, Int. J. Mod. Phys. A 32 (2017) no.05, 1750024 [arXiv:1701.06894 [hep-th]].
S. Shiba and H. Sugawara, arXiv:1709.07169 [hep-th].

Part1: Chiral algebras and Schur index of N=2 SCFTs / Part2: N=2 S-duality revisited

When:2017/11/24 (Fri.) 13:30-16:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Takahiro Nishinaka (Ritsumeikan Univ.)
Abstract:In the first part of this talk, I will review two-dimensional chiral algebras associated with 4d N=2 superconformal field theories (SCFTs). The associated chiral algebra is especially useful for studying strongly coupled SCFTs. I will particularly review the list of 4d superconformal multiplets that contain BPS local operators mapping to 2d chiral algebra operators.

In the second part, I will talk about our own work on the chiral algebra of an exotic Argyres-Douglas (AD) theory. This AD theory arises in the strong coupling limit of an exactly marginal SU(3) gauging of simpler AD theories (plus fundamental hypermultiplets), and therefore is an AD version of the Minahan-Nemeschansky E_6 theory arising in the strong coupling limit of the SU(3) gauge theory with six flavors. We argue that this exotic AD theory splits into a free hypermultiplet and a smaller exotic AD theory. We then construct the associated chiral algebra for the latter AD theory, which turns out to be an exotic W-algebra that exists only for special values of the Virasoro central charge.
Reference: C. Beem, M. Lemos, P. Liendo, W. Peelaers, L. Rastelli, B.C. van Rees, arXiv:1312.5344 [hep-th], M. Buican, Z. Laczko, T. Nishinaka, arXiv:1706.03797 [hep-th]

The supersymmetric affine Yangian

When:2017/11/24 (Fri.) 10:30-12:00
Where:Honkan (Main Bldg.) H155B
Speaker:Hong Zhang (ITP, Beijing)
Abstract:The affine Yangian of gl1 is known to be isomorphic to $W_{1+∞}$, the W- algebra that characterizes the bosonic higher spin – CFT duality. In this paper we propose defining relations of the Yangian that is relevant for the N = 2 superconfor- mal version of $W_{1+∞}$. Our construction is based on the observation that the N = 2 superconformal $W_{1+∞}$ algebra contains two commuting bosonic $W_{1+∞}$ algebras, and that the additional generators transform in bi-minimal representations with respect to these two algebras. The corresponding affine Yangian can therefore be built up from two affine Yangians of gl1 by adding in generators that transform appropriately.
Reference:

TBA

When:2017/11/22 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kazumi Okuyama (Shinshu Univ.)
Abstract:TBA
Reference:

ABJM理論の非摂動効果とその周辺

When:2017/11/20 (Mon.) 10:45-16:35
Where:Honkan (Main Bldg.)H113
Speaker:Kazumi Okuyama (Shinshu Univ.)
Abstract:[日程]
11月20 (月) 10:45-12:15 13:20-14:50 15:05-16:35
11月21 (火) 10:45-12:15 13:20-14:50 15:05-16:35
11月22 (水) 10:45-12:15 13:20-14:50


[講義の目的]
M2ブレーンの低エネルギー有効作用であるABJM理論は、AdS/CFT対応によりAdS(4)xS(7)上のM理論に対応している。ABJM理論の球面上の分配関数の解析から、M理論の非摂動効果の理解に最近大きな進展があった。この講義では、ABJM理論の非摂動効果について概観する。

[講義計画]
1. 非摂動効果の概観
2. ABJM模型のplanar極限
3. フェルミガス表示
4. 量子周期とNekrasov-Shatashvili極限
5. 厳密な大分配関数の例
6. 関連する話題

[教科書・参考書等]
特になし
Reference:

Reflection States in Ding-Iohara-Miki Algebra and Brane-Web for D-type Quiver

When:2017/11/08 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Masayuki Fukuda (Tokyo Univ. )
Abstract:Instanton partition functions of N=1 5d Super Yang-Mills reduced on S1 can be engineered in type IIB string theory from the (p,q)-branes web diagram. To this diagram is superimposed a web of representations of the Ding-Iohara-Miki (DIM) algebra that acts on the partition function. In this correspondence, each segment is associated to a representation, and the (topological string) vertex is identified with the intertwiner operator constructed by Awata, Feigin and Shiraishi. We define a new intertwiner acting on the representation spaces of levels (1,n)⊗(0,m)→(1,n+m), thereby generalizing to higher rank m the original construction. It allows us to use a folded version of the usual (p,q)-web diagram, bringing great simplifications to actual computations. Moreover, reflection states are introduced in the vertical and horizontal modules of the DIM. Extending the correspondence to the vertical reflection states, it is possible to engineer the N=1 quiver gauge theory of D-type (with unitary gauge groups). In this way, the Nekrasov instanton partition function is reproduced from the evaluation of expectation values of intertwiners. This computation leads to the identification of the vertical reflection state with the orientifold plane of string theory.
Reference:

A 2D dilaton gravity model with hyperbolic potential

When:2017/11/01 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Hideki Kyono (Kyoto Univ.)
Abstract:Recently, 2D dilaton gravity is drawing attention as a toy model of holography. We consider a system with a hyperbolic dilaton potential associated with an integrable deformation of the Almheiri-Polchinski model. Even in the deformed case, the system has the general solution. Especially, it has a black hole solution and we reproduce its Bekenstein-Hawking entropy from the viewpoint of the boundary stress tensor by taking an appropriate counterterm. Finally, we will discuss some solutions with matter fields. This seminar talk is based on our recent works (arXiv: 1701.06340 and 1704.07410) with S.Okumura and K. Yoshida.
Reference:arXiv:1701.06340, arXiv:1704.07410

Fermion scattering amplitudes from gauge-invariant actions for open superstring field theory

When:2017/10/13 (Fri.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Hiroki Sukeno (Univ. Tokyo, Komaba)
Abstract:Superstring field theory is a formulation of superstring theory based on the spacetime gauge invariance. On the other hand, an essential ingredient that ensures decoupling of unphysical degrees of freedom in the world-sheet theory is the integration over the supermoduli space of super-Riemann surfaces. It is important to understand how this integration over the supermoduli space is implemented in superstring field theory based on spacetime gauge invariance.

In this talk, we calculate on-shell scattering amplitudes involving fermions at the tree level in open superstring field theory. In particular, we calculate four-point and five-point amplitudes from open superstring field theory constructed by Kunitomo and Okawa, and we elucidate how the amplitudes in the world-sheet path integral with the standard prescription using picture-changing operators are reproduced.
Reference:arXiv:1612.00777

Supermatrix Chern-Simons Model

When:2017/09/20 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Tadashi Okazaki (National Taiwan University)
Abstract:We will discuss matrix Chern-Simons quantum mechanics. The model is known to be equivalent to the Calogero model and is proposed as an effective theory of quantum Hall states and of vortices in Chern-Simons theory. Recently Dorey, Tong and Turner generalized the model (arXiv:1603.09688, arXiv:1604.05711) and demonstrate that it can capture more general quantum Hall states with spin degrees of freedom of underlying electrons. Also in the large N limit, it turns out to be closely related to the WZW model. We will review several aspects of the model involving recent results and discuss ongoing work which is a further generalization of this matrix model whose symmetry group is extended to a supergroup.
Reference:

$\mathcal{N}=1$ Deformations and RG Flows of $\mathcal{N}=2$ SCFTs

When:2017/07/26 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kazunobu Maruyoshi (Seikei Univ.)
Abstract:We study certain $\mathcal{N}=1$ preserving deformations of four-dimensional $\mathcal{N}=2$ superconformal field theories (SCFTs) with non-Abelian flavor symmetry. The deformation is described by adding an $\mathcal{N}=1$ chiral multiplet transforming in the adjoint representation of the flavor symmetry with a superpotential coupling, and giving the nilpotent vacuum expectation value to the chiral multiplet. Remarkably, we find classes of theories flow to $\mathcal{N}=2$ supersymmetric fixed points in the infrared under the deformation. In particular, we find renormalization group flows from the deformed conformal SQCDs with gauge group $SU(N)$ and $Sp(N)$ to $\mathcal{N}=2$ SCFTs of Argyres-Douglas type. From these "Lagrangian descriptions," we compute the full superconformal indices and find agreements with the previous results.
This talk is based on the collaboration with Prarit Agarwal and Jaewon Song, and arXiv:1606.05632, arXiv:1607.04281, arXiv:1610.05311.
Reference:arXiv:1606.05632, arXiv:1607.04281, arXiv:1610.05311.

Refined large N duality for knots

When:2017/07/12 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Masaya Kameyama (Nagoya Univ.)
Abstract:I will talk about large N duality of refined Chern-Simons theory with a knot.
Chern-Simons theory provides a natural framework of quantum invariants of three-manifolds and knots and it is known that its large N limit is dual to topological string theory on the resolved conifold.
Motivated by knot homology, refinements of Chern-Simons theory, BPS states and topological string have been studied since Gukov-Schwarz-Vafa’s work.
Our formulation gives a relation between refined Chern-Simons invariants of a knot and refined BPS states in the resolved conifold, which is a generalization of the work of Labastida-Mrino-Ooguri-Vafa in refined topological string theory, and extends the proposal of Gukov-Schwarz-Vafa to any colors.
Reference:arXiv:1703.05408

2017 年度 第 1 回日露ワーキングセミナー

When:2017/07/08 (Sat.) 10:30-15:30
Where:Honkan (Main Bldg.) H2-39
Speaker:今野 均$^a$, 初田泰之$^b$ ($^a$東京海洋大学, $^b$立教大学)
Abstract:Talk1: 10:30~12:30
Speaker: 今野 均(東京海洋大学)
Title: 楕円量子群 U_{q,p}(\widehat{\mathfrak{g}}) の表現と応用:楕円q-KZ方程式, 楕円重み関数, Gelfand-Tsetlin基底上の有限次元表現
Abstract: 最初に, 楕円可解格子模型などとの関連から楕円量子群
U_{q,p}(\widehat{\mathfrak{g}})を 定式化した経緯や, 3通りの定式化, quasi-Hopf algebra {\cal B}_{q,\lambda}(\widehat{\mathfrak{g}}), FRST流(Felderの楕円量子群), Drinfeld流 U_{q,p}(\widehat{\mathfrak{g}}), 相互の関連について簡単に話をする. 続いて, 最近得た結果に基づいて U_{q,p}(\widehat{\mathfrak{ sl}}_N) の表現を用いた楕円 q-KZ方程式の形式的積分解の導出, 特にその被積分関数に現れる楕円重み関数の導出とその性質, 及びそれらと U_{q,p}(\widehat{\mathfrak{ gl}}_N) のGelfand-Tsetlin基底上の
有限次元表現との関連について述べる. この表現は Vasserotや中島による量子アフィン代数U_q(\widehat{\mathfrak{g}}) の同変K理論上の幾何学的表現の自然な楕円関数型拡張になっている. 楕円重み関数は, Aganagic-Okounkovによって同変楕円コホモロジーに付随して定式化された楕円stable envelopに同一視され, また, その対応に基づいて, Gelfand-Tsetlin基底上の有限次元表現は同変楕円コホモロジー上の幾何学的表現を与えることが期待される. 時間があれば, 量子 q -Langlands双対性についても触れる.

Talk2: 13:30~15:30
Speaker: 初田泰之(立教大学)
Title: Calabi-Yau geometry and electrons on 2d lattices
Abstract: I will talk about our recent results on a novel relation between toric Calabi-Yau geometry and certain electron systems on 2d lattices. It turns out that the modular double duality, known in quantum group, plays an important role.
Reference:

Supersymmetric Renyi Entropy and Defect Operators

When:2017/07/05 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Tatsuma Nishioka (Univ. of Tokyo , Hongo)
Abstract:We describe the defect operator interpretation of the supersymmetric Renyi entropies of superconformal field theories in three, four and five dimensions. The operators involved are supersymmetric codimension-two defects in an auxiliary Z_n gauge theory coupled to n copies of the SCFT. We compute the exact expectation values of such operators using localization, and compare the results to the supersymmetric Renyi entropy. The agreement between the two implies a relationship between the partition function on a squashed sphere and the one on a round sphere in the presence of defects.
Reference:arXiv:1612.02894

On confinement in Yang-Mills theory

When:2017/06/28 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kazuya Yonekura (Kavli IPMU)
Abstract:I will discuss some aspects of confinement in Yang-Mills theory in a weak coupling setup. The theory is put on a three-dimensional torus, and the relation between four dimensional Yang-Mills theory and two dimensional CPN model is discussed and used to derive properties of Yang-Mills theory in the confining phase. Then the vacuum structure of Yang-Mills theory which are usually associated to strong coupling dynamics will be discussed in completely weakly coupled regime.
Reference:arXiv:1704.05852, arXiv:1706.06104

Refined geometric transition and qq-characters

When:2017/06/21 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Yuji Sugimoto (Osaka Univ.)
Abstract:We provide the refined prescription for the geometric transition in the refined topological string theory and show how to apply it to constructing doubly quantized Seiberg-Witten curves called qq-characters. In the arguments of literatures for the refined geometric transition, it was not seriously considered that the choice of the preferred direction may affect the open string amplitude. Our prescription given here for the refined geometric transition is involved in nontrivial effects from sensitivity to the preferred direction. As its application, we discuss the description of the qq-character that was recently well-developed but whose stringy origin is still unclear. It is proposed that it can be engineered by the refined geometric transition, which may possibly give interpretation in terms of string theory.
Reference:arXiv:1705.03467

Calabi-Yau geometry and electrons on 2d lattices

When:2017/06/16 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Yasuyuki Hatsuda (Rikkyo Univ.)
Abstract:I will talk about our recent results on a novel relation between toric Calabi-Yau geometry and certain electron systems on 2d lattices. It turns out that the modular double duality, known in quantum group, plays an important role.
Reference:arXiv:1701.01561

On the transverse M5-branes in matrix theory

When:2017/05/31 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Shinji Shimasaki (Keio University)
Abstract:It has been a long-standing problem how the transverse M5-branes are described in the matrix-model formulations of M-theory. We consider this problem for M-theory on the maximally supersymmetric pp-wave geometry, which admits transverse spherical M5-branes with zero light-cone energy. By using the localization, we directly analyze the strong coupling region of the corresponding matrix theory called the plane wave matrix model (PWMM). Under the assumption that the low energy modes of the scalar fields in PWMM become mutually commuting in the strong coupling region, we show that the eigenvalue density of the SO(6) scalars in the low energy region exactly agrees with the shape of the spherical M5-branes in the decoupling limit. This result gives a strong evidence that the transverse M5-branes are indeed contained in the matrix theory and the theory realizes a second quantization of the M-theory.
Reference:arXiv:1701.07140