Einstein Gravity from Matrix Integral indico link

Date: May 9th, 18:00AM(JST)
Speaker: Shota Komatsu (CERN)
Title: Einstein Gravity from Matrix Integral

Abstract: We formulate and test holography between a supersymmetric mass deformation of the Ishibashi-Kawai-Kitazawa-Tsuchiya (IKKT) matrix model and type IIB supergravity backgrounds with exceptional F4 supersymmetry. This is arguably the simplest example of holography in which the dual description contains Einstein gravity. We conjecture a one-to-one correspondence between saddle points of matrix integral and supergravity backgrounds, and test it through the supersymmetric localization of the matrix integral.

Perturbatively exact supersymmetric partition functions of ABJM theory on Seifert manifolds and holography indico link

Date: March 14th (Fri), 9:00AM (JST)
Speaker: Junho Hong (Sogan U.)
Title: Perturbatively exact supersymmetric partition functions of ABJM theory on Seifert manifolds and holography

Abstract: I will introduce the supersymmetric partition function of ABJM theory on a U(1) fibration over a Riemann surface, evaluating it to all orders in the 1/N -perturbative expansion up to exponentially suppressed corrections via the Bethe formulation. Through holographic duality, this result is matched with the regularized on-shell action of a dual Euclidean AdS 4-Taub-Bolt background incorporating 4-derivative corrections, and also provides valuable insights into the logarithmic corrections that emerge from the 1-loop calculations in M-theory path integrals. In this process, I will also revisit the Euclidean AdS4-Taub-Bolt background carefully, elucidating the flat connection in the background graviphoton field. This analysis umambiguously determines the U(1)R holonomy along the Seifert fiber, thereby solidifying the holographic comparison regarding the partition function on a large subclass of Seifert manifolds.

Double-Scaled SYK, de Sitter Space, and QCD indico link

Date: January 24th, 9:00AM(JST)
Speaker: Yasuhiro Sekino (Takushoku U.)
Title: Double-Scaled SYK, de Sitter Space, and QCD

Abstract:
A surprising connection exists between double-scaled SYK (DSSYK) model at infinite temperature, and large-N QCD. The large N expansions of the two theories have the same form; the 't Hooft limit of QCD parallels the fixed p limit of SYK (with p-fermion interactions), and the limit of fixed gauge coupling g---the flat space limit in AdS/CFT---parallels the double-scaled limit of SYK. From the holographic perspective fixed g is the far more interesting limit of gauge theory, but very little is known about it. DSSYK allows us to explore it in a more tractable way. The connection is illustrated by perturbative and non-perturbative DSSYK calculations, and comparing the results with known properties of Yang Mills theory. The correspondence is largely independent of the conjectured duality between DSSYK and de Sitter space, but may have a good deal to tell us about it. (Based on work with L. Susskind.)

M2-M5 giant graviton expansions indico link

Date: November 29 (Fri), 17:30 (JST)
Speaker: Tadashi Okazaki (Yau Center of Southeast University)
Title: M2-M5 giant graviton expansions

Abstract: We investigate exact closed-forms for supersymmetric indices of the theories describing a stack of N M2-branes and their giant graviton expansions. We demonstrate that M2-branes can hold a lesson for M5-branes and vice versa via the reversible giant graviton expansions of the indices. Consequently, we obtain several exact closed-form expressions for the indices of 6d (2,0) theory describing a stack of N M5-branes. The talk will be based on the collaborative work with Hirotaka Hayashi and Tomoki Nosaka [arXiv: 2409.13239].

Black Hole from Entropy Maximization indico link

Date: October 8 (Tue), 9:00(JST)
Speaker: Yuki Yokokura (RIKEN)
Title: Black Hole from Entropy Maximization

Abstract: The identity of a black hole is still mysterious theoretically and observationally. It has the thermodynamic entropy (the Bekenstein-Hawking entropy). According to quantum theory and thermodynamics, the origin of thermodynamic entropy is quantum mechanical. Therefore, a black hole should be essentially a quantum object. So, what is the quantum definition/characterization of black holes? One candidate motivated by (local) holography and thermodynamics is that a black hole maximizes thermodynamic entropy for a given (expectation value of) surface area. As a step toward exploring this possibility, we study the entropy of various highly-excited spherical static configurations in the 4D semi-classical Einstein equation with many matter fields, and reach uniquely the entropy-maximizing configuration. That is, self-gravitating quanta condensate into a radially-uniform dense configuration with no horizon, where the self-gravity and a large quantum pressure induced by the curvatures are balanced and no singularity appears. The interior metric is a self-consistent and non-perturbative solution for Planck's constant. The maximum entropy, given by the volume integral of the entropy density, agrees exactly with the Bekenstein-Hawking formula through the self-gravity, leading to the Bousso bound for thermodynamic entropy. Finally, we see a speculative view that the configuration represents semi-classically a quantum-gravitational condensate. [arXiv:2309.00602]

Asymptotically Safe Quantum Gravity and Essential RG indico link

Date: 27 August (Tue) 17:30 (JST)
Speaker: Nobuyoshi Ohta (Kindai U./APCTP)
Title: Asymptotically Safe Quantum Gravity and Essential RG

Abstract: We first explain one of the approaches to quantum gravity based on the Functional Renormalization Group, what is called asymptotic safety. The main issue is how to control the high energy behavior of the gravity theory, keeping predictability without ghosts (negative metric states). Asymptotic safety tries to achieve this goal by finding UV fixed points of the finite number of the gravitational couplings. We discuss how to deal with the wave function renormalization, which is one of the inessential couplings, which do not affect physical quantities. We find that higher derivative operators are necessary but with Gaussian fixed point. This leads to negative metric states. We suggest that a possible resolution of this conflict may be the essential RG which deals with only the essential couplings.

Field theory for branes and higher-form symmetry indico link

Date: July 18th (Thu), 9:00(JST)
Speaker: Kiyoharu Kawana (KIAS)
Title: Field theory for branes and higher-form symmetry

Abstract: We propose field theory for branes with higher-form symmetry. The field \psi is no longer a mere function of spacetime point but a functional of p-dimensional closed brane C_p embedded in a spacetime. We show that it is possible to construct an action that is invariant under higher-form transformation by utilizing the “area derivative”, which is a generalization of ordinary derivative \partial/\partial X^\mu. Then, we discuss various fundamental properties of this theory. The classical solution exhibits the area law in the unbroken phase of p-form symmetry, while it indicates a constant behavior (Perimeter law) in the broken phase. In the latter case, the low-energy effective theory is described by the p-form Maxwell theory. 
When time permits, I will also discuss gauged version of the brane-field theory and show that it is indeed a generalization of the Ginzburg-Landau theory for superconductivity.

Universal Spectrum of Superconformal Field Theory and Holography indico link

Date: June 11 (Tue), 17:30 (JST)
Speaker: Jaewon Song (KAIST)
Title: Universal Spectrum of Superconformal Field Theory and Holography

Abstract: In the celebrated work of Cardy, he derived universal formula for the density of states at high-temperature in two-dimensional CFT. We study an analog of Cardy’s formula of in four-dimensional superconformal theory (SCFT). We also find that large N limit of the 4d supersymmetric index agrees with the Cardy limit when underlying theory is ‘holographic,’ meaning that it admits a dual AdS5 description. We apply the large N formula for the supersymmetric index to model an information loss problem in quantum gravity. Here we find that non-perturbative saddles that correspond to orbifolded Euclidean black holes play a crucial role to cure the “information loss.”