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次回のセミナー (Next Seminar)


When:2019/12/13 (Fri.) 13:00-14:00
Where:Honkan (Main Bldg.) H2-84A
Speaker:Hirotaka Hayashi (Tokai Univ.)

最近のセミナー (Recent Seminars)


When:2020/02/03 (Mon.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Seyed Morteza Hosseini (Kavli IPMU)


When:2019/12/18 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Yasuyuki Hatsuda (Rikkyo Univ.)


When:2019/12/13 (Fri.) 13:00-14:00
Where:Honkan (Main Bldg.) H2-84A
Speaker:Hirotaka Hayashi (Tokai Univ.)

Entropy of the Janus interface in four-dimensional N=2 superconformal field theories

When:2019/11/13 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Lento Nagano (Tokyo Univ.)
Abstract:We construct an co-dimension 1 defect, called the Janus interface, in four-dimensional N=2 superconformal field theories across which a coupling constant changes its value.
We then define its entropy as a contribution to entanglement entropy and show that the entropy associated to the Janus interface is given by a ratio of partition functions with and without the interface.
By using this fact, we compute the entropy of the Janus interface to show that it is proportional to a particular linear combination of analytically continued Kahler potentials, as conjectured in 1805.09981 by Goto and Okuda.
This presentation is based on a work in progress with K. Goto, T. Nishioka, and T. Okuda.

Topological order in the color-flavor locked phase of (3+1)-dimensional U(N) gauge-Higgs system

When:2019/11/01 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-84A
Speaker:Ryo Yokokura (KEK)
Abstract:We study a (3+1)-dimensional U(N) gauge theory with N-flavor fundamental scalar fields, whose color-flavor locked (CFL) phase has topologically stable non-Abelian vortices. The U(1) charge of the scalar fields must be Nk+1 for some integer k in order for them to be in the representation of U(N) gauge group. This theory has a Z_{Nk+1} one-form symmetry, and it is spontaneously broken in the CFL phase, i.e., the CFL phase is topologically ordered if k is not 0. We also find that the world sheet of topologically stable vortices in CFL phase can generate this one-form symmetry.

Dirac quantization and Maxwell anomaly in string theory

When:2019/10/30 (Wed.) 16:15-17:15
Where:Honkan (Main Bldg.) H284
Speaker:Kazuya Yonekura (Tohoku University)

Linearized Field Equations of Gauge Fields from the Entanglement First Law

When:2019/10/25 (Fri.) 13:00-14:00
Where:Honkan (Main Bldg.) H2-84A
Speaker:Kenta Hasegawa (Saitama Univ.)
Abstract:In the context of the AdS/CFT correspondence linearized field equations of vector and antisymmetric tensor gauge fields around an AdS background are obtained from the entanglement first law of CFTs. The holographic charged entanglement entropy contains a term depending on the gauge field in addition to the Ryu-Takayanagi formula.

Wall-crossing and operator ordering for 't Hooft operators in N=2 gauge theories

When:2019/07/24 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Takuya Okuda (Univ. of Tokyo, Komaba)
Abstract:In this talk I will report on a joint work with H. Hayashi and Y. Yoshida on 't Hooft operators. We study half-BPS 't Hooft line operators in 4d N=2 gauge theories on S^1 x R^3 with omega-deformation. Non-perturbative contributions, namely monopole screening contributions, to the correlator of 't Hooft operators can be computed using quiver supersymmetric quantum mechanics. We show that for a gauge group U(N) there is a direct relation between a chamber in the space of FI parameters of SQM's and the ordering of 't Hooft operators. For U(N) SQCD with N_F flavors, wall-crossing occurs only when a minimal 't Hooft operator passes another minimal operator of a different kind and their ordering changes. We demonstrate this by working out several examples.


When:2019/07/17 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Toshihiro Ota (RIKEN)

Holographic Complexity in the Jackiw-Teitelboim Gravity

When:2019/07/10 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kanato Goto (RIKEN)
Abstract:In the last few years, a deep connection between spacetime geometry and quantum information theoretic properties has been found in the context of AdS/ CFT correspondence. The most famous example is the so-called Ryu-Takayanagi formula which relates the area of the co-dimension two surface in AdS to the entanglement entropy in the CFT. Recently, a new gravity/information connection was found between the size of the interior region of black holes in AdS and the computational complexity in the CFT.
In joint work with Marrochio, Myers, Queimada, and Yoshida, we analyzed the behavior of the holographic complexity in the so-called Jackiw-Teitelboim model (JT model), which is the two-dimensional dilaton gravity theory which describes the nearly AdS2 geometry. In the Complexity=Action proposal, we showed that the late-time growth rate vanishes for the JT model. This vanishing complexity mirrors the behavior for the magnetic Reissner-Nordstrom-AdS black holes in four dimensions, which play a role in constructing the JT action via dimensional reduction. This situation can be ameliorated by instead considering a dimensional reduction describing the near-horizon physics of near-extremal electric black holes in four dimensions. We found that in the resulting two-dimensional dilaton gravity theory, which we call JT-like theory, the late time growth rate is non-vanishing and it approaches the value of the Lloyd bound.
In four dimensions, there is a boundary term involving the Maxwell field, which one can add to the gravitational action. We also considered the dimensional
reduction of the Maxwell boundary term and found that it changes the late time behavior of the complexity for both cases.

Argyres-Douglas Theories and Liouville Irregular States

When:2019/07/03 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Takahiro Uetoko (Ritsumeikan univ.)
Abstract:We study irregular states of rank-two and three in Liouville theory, based on an ansatz proposed by D. Gaiotto and J. Teschner. Using these irregular states, we evaluate asymptotic expansions of irregular conformal blocks corresponding to the partition functions of $(A_1,A_3)$ and $(A_1,D_4)$ Argyres-Douglas theories for general $\Omega$-background parameters. In the limit of vanishing Liouville charge, our result reproduces strong coupling expansions of the partition functions recently obtained via the Painleve/gauge correspondence. We also find that our partition functions are invariant under the action of the Weyl group of flavor symmetries once four and two-dimensional parameters are correctly identified. We finally propose a generalization of this parameter identification to general irregular states of integer rank.

The memory effect of Entanglement in 2D CFTs

When:2019/06/24 (Mon.) 16:00-18:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Song He (Jilin University, Professor)
Abstract:We will talk about the memory effect of entanglement entropy of locally excited states in two-dimensional conformal field theories (CFTs). In particular, we consider excited states obtained by acting on a vacuum with primary operators. We show that the entanglement entropy increases by a finite constant amount under its time evolution.
Moreover, in rational conformal field theories, we prove that this increase of the (both Renyi and von Neumann) entanglement entropy always coincides with the log of the quantum dimension of the primary operator. Further, we also show the behavior of the time evolution of Entanglement in 2D quantum gravity and WCFTs. If the time is allowed, we will talk about the recent progress on this object in various deformed field theory.

Triangle anomalies and nonrelativistic Nambu-Goldstone modes of generalized global symmetries

When:2019/06/19 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Noriyuki Sogabe (Keio university)
Abstract:In massless QCD coupled to QED in an external magnetic field, a photon with the linear polarization in the direction of the external magnetic field mixes with the charge neutral pion through the triangle anomaly, leading to one gapless mode with the quadratic dispersion relation $ω$∼$k^2$ and one gapped mode. In this talk, we show that this gapless mode can be interpreted as the so-called type-B Nambu-Goldstone (NG) mode associated with the spontaneous breaking of generalized global symmetries and that its presence is solely dictated by the anomalous commutator in the symmetry algebra. We also argue a possible realization of such nonrelativistic NG modes in $3$-dimensional Dirac semimetals.


When:2019/06/10 (Mon.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Naoki Sasakura (YITP)

Deep learning & holographic QCD

When:2019/05/29 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Akinori Tanaka (Riken)
Abstract:There is no doubt about that the deep learning (DL) is the one of the recent epoch-making achievement of the science.
Recently, there are some movements in scientific community to apply DL or machine learning techniques to study their research fields.
Even particle physics and string theory are not out of that movements.
In this talk, I will review the concept of DL and our proposal to apply it to find gravity dual of given field theory.
After that, I talk on our recent application in the context of holographic QCD.
Reference:Physical Review D, 98(4), 046019.(arXiv:1802.08313)
Physical Review D, 98(10), 106014.(arXiv:1809.10536)

Super instanton counting and localization

When:2019/05/08 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Taro Kimura (Keio university)
Abstract:We study the super instanton solution in the gauge theory with $U(n_+|n_−)$ gauge group. Based on the ADHM construction generalized to the supergroup theory, we derive the instanton partition function from the super instanton moduli space through the equivariant localization. We derive the Seiberg–Witten geometry and its quantization for the supergroup gauge theory from the instanton partition function, and study the connection with classical and quantum integrable systems. We also argue the brane realization of the supergroup quiver gauge theory, and possible connection to the non-supergroup quiver gauge theories.

Anomaly, regularization and partition function on lens space

When:2019/04/24 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Shuichi Yokoyama (YITP)
Abstract:In this talk, I will speak about how to derive a correct phase factor in partition function of N=2 SUSY gauge theory on three-manifold using three-sphere and lens space.
In particular we reproduce a holonomy dependent phase factor associated Chern-Simons term derived by Imamura-Matsuno-Yokoyama from a fermion 1-loop determinant of regularization ghost for a vector multiplet.
Our result improves their work on lens space partition function, and passes a couple of duality tests including the total phase.

Correlation Functions on the 1/2-BPS Wilson Loop: Perturbation and Integrability

When:2019/02/22 (Fri.) 13:30-15:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Naoki Kiryu (Tokyo U., Komaba )
Abstract:We study correlation functions of local operators inserted on the 1/2-BPS Wilson loop in planar N = 4 supersymmetric Yang-Mills theory in four dimensions. This is consistent with a holographic description of the correlators of open strings attached to D-branes in AdS5×S5. We first conjecture the finite coupling expression of the correlators in view of the integrability-based approach called “hexagonalization”, which was introduced previously to study the correlation functions in the absence of the Wilson loop. We next perform direct perturbative computation. Through the comparison with “hexagonalization”, we refine the conjecture for the integrability-based approach to the correlators on the 1/2-BPS Wilson loop.
Reference:arXiv:1706.02989, arXiv:1710.07325, arXiv:1812.04593.

4次元N=2超共形場理論におけるBPSセクターにおけるOPE selection ruleの決定

When:2019/01/30 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Kazuki Kiyoshige (大阪市立大学)
Abstract:Argyres-Douglas型の超共形場理論(SCFT)を始め、4次元N=2にはラグランジアンがないとされる非自明なSCFTが多数存在する。これらの理論の解析は演算子積展開(OPE)やindexなどの手法で行うことが主流になる。そこで我々は超共形代数の性質から決まるBPS条件を用いてOPE selection rule を決定した。本研究では、(S)CFTにおいて特に重要なstress tensor と2d chiral algebra と関連のあるSchur 多重項と呼ばれるBPSセクターについてのselection rule (stress tensor × Schur multiplet)に絞って解析を行った。またそれらのselection rule から一般的な性質を予想した。
このトークはarXiv:1812.06394 [hep-th](西中氏との共同研究)に基づく。

Monodromifold planes: Refining $[p,q]$-branes and orientifold planes in string theory

When:2019/01/23 (Wed.) 16:00-17:00
Where:Honkan (Main Bldg.) H2-39
Speaker:Naoto Kan (SOKENDAI)
Abstract:F-theory is the non-perturbative compactification of type IIB superstring theory. The compact space of F-theory has the structure of elliptic fibrations, which describe the compactification of type IIB string with the 7-branes background. The elliptic fibration is written by the Weierstrass form. In particular when we choose the base space as $\mathbb{P}^1$, then the whole of the compact space become the rational elliptic surface (RES) or the K3 surface. Furthermore, the discriminant loci of the Weierstrass form correspond to the D7-branes. On the other hand, the singularities of such a RES or K3 surface is classified by Kodaira, and B-branes and C-branes (or $[p,q]$-brane in general) with a monodromy emerge at singular points. The origin of such a monodromy can be thought of as f- and g-locus planes (named monodromifold planes) in the Weierstrass form. In this talk, I will start with the review of type IIB superstring theory and F-theory compactification and discuss the properties of monodromifold planes.
Reference:Shin Fukuchi, Naoto Kan, Shun'ya Mizoguchi and Hitomi Tashiro,
"Monodromifold planes: Refining (p,q)-branes and orientifold planes in
string theory,"

Spinning conformal defects

When:2018/12/07 (Fri.) 13:30-14:30
Where:Honkan (Main Bldg.) H2-39
Speaker:Nozomu Kobayashi (Kavli IPMU)
Abstract:We consider conformal defects with spins under the rotation
group acting on the transverse directions. They are described in the
embedding space formalism in a similar manner to spinning local
operators, and their correlation functions with bulk and defect local
operators are determined by the conformal symmetry. The operator product
expansion (OPE) structure of spinning conformal defects is examined by
decomposing it into the spinning defect OPE block that packages all the
contribution from a conformal multiplet. The integral representation of
the block derived in the shadow formalism is facilitated to deduce
recursion relations for correlation functions of two spinning conformal
defects. In simple cases, we construct spinning defect correlators by
acting differential operators recursively on scalar defect correlators.
Reference:arXiv:1805.05967 [hep-th]