**Upcoming talk:**

**Title: **One-loop exactness of Schwarzian theory

**Speaker: **Yixiao Tao

**Date:** Wednesday 31 May 2023

**Time: **11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

In this talk I will explain why Schwarzian theory is one-loop exact using the Duistermaat-Heckman (DH) formula. Then I will generalize our discussion to coadjoint orbits of the Virasoro group.

ref: 1703.04612

**Past talks:**

**Title: **Correlation Functions in JTbar Deformed CFT

**Speaker: **Juntao Wang

**Date: **Wednesday 24 May 2023

**Time: **11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

In this talk some work on correlation functions in JTbar deformed 2d CFT will be reviewed. Given the special structure of the JTbar operator, the general form of the left-moving part correlation functions could be obtained by using constraints from the remained conformal symmetry, as well as conservation of momentum and charge. Furthermore, the deformed left-moving conformal weight and the deformed charge are exactly tractable non-perturbatively and can be tested by using the first (possibly second) order conformal perturbation calculation. This talk is mainly based on arxiv:1902.01434 and arxiv:1907.03745.

**Title:** A story of chords, wormholes, and complexity

**Speaker:** Kevin Loo

**Date: **Wednesday 17 May 2023

**Time: **11:30-13:30 (Beijing time)

**Venue:** Ning Zhai W11

**Abstract: **

The concept of complexity is well known in holographic duality, although its precise definition is still debatable. Under JT/DSSYK (double-scaled SYK) duality, one special class of complexity, known as Krylov complexity, of boundary theory is recently shown to be dual to the length of a two-sided wormhole in JT gravity. This result made extensive use of chord diagram techniques. I will briefly introduce this idea following [2305.04355].

**Title:** Bulk local probes from the boundary

**Speaker: **Reiko Liu

**Date: **Wednesday 10 May 2023

**Time: **11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

In this talk, I will review the extrapolation dictionaries in AdS, dS (and perhaps flat spacetime), and then discuss the constructions of local probes from the timelike, spacelike, and null boundaries. In d = 3, the local probes can also be constructed from the gravitational Wilson lines, and I will finally compare these different approaches.

**Title:** Emergent spacetime from von Neumann subalgebra

**Speaker: **Wenxin Lai

**Date:** Wednesday 26 April 2023

**Time:** 11:30-13:30 (Beijing time)

**Venue:** Ning Zhai W11

**Abstract: **

It is proposed that a boundary von Neumann subalgebra is dual to a bulk causally complete subregion. This serves as a more rigorous generalization of the old-fashioned subregion duality. I will briefly introduce this idea, following the work of Sam Leutheusser and Hong Liu (2212.13266).

**Title: **Pseudo Entropy and Timelike entanglement entropy

**Speaker: **Pengxiang Hao

**Date: **Wednesday 19 April 2023

**Time: **11:30-13:30 (Beijing time)

**Venue:** Ning Zhai W11

**Abstract: **

Pseudo entropy is the von Neumann entropy of a reduced transition matrix, which generalizes entanglement entropy in that it depends on both an initial and a final state. A complex-valued measure called the timelike entanglement entropy is a special kind of pseudo entropy. I will give a brief introduction to the basic properties of pseudo entropy and then discuss the holographic dual of the TEE.

Refs: 2302.11695, 2005.13801

**Title:** TTbar deformation as random geometry

**Speaker:** Kangning Liu

**Date: **Wednesday 12 April 2023

**Time:** 11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

In this talk, I will introduce an equivalent definition of TTbar deformation of 2d QFTs, i.e. TTbar deformation as a path integral of an auxiliary metric field, based on the work of Cardy. The flow equation satisfied by the torus partition function will be derived, which is consistent with Zamolodchikov's result. Moreover, the formalism can be applied to general domains with boundaries, and the examples of a finite cylinder and a disk will be presented.

Ref: 1801.06895

**Title: **Wilson Lines and Ishibashi States in AdS3/CFT2

**Speaker:** Zhengyuan Du

**Date: **Wednesday 29 March 2023

**Time: **11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

First I will talk about some basic concepts of gravitational Wilson line and Ishibashi states. Then I will talk about the relation between Wilson line and Green function on spacetime, building local bulk fields and CFT interpretation.

Refs: 1805.05398

**Title:** Flat holography and dual field theory

**Speaker: **Zehua Xiao

**Date:** Wednesday 22 March 2023

**Time:** 11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

It is conjectured that the gravity theory in (D+1) asymptotically flat spacetime is dual to the D-dimensional Carrollian conformal field theory (CCFT) on the null infinity. In this talk, I will first introduce the conjecture of flat/CCFT holography. Then I will talk about the construction of the Carroll group, the conformal Carroll group, the Lie algebra of Carrollian conformal symmetry and the highest weight representation. Finally, I will discuss the Carrollian conformal electrodynamics and Yang-Mills theory without matter coupling as two examples of the dual CCFTs.

References: 1609.06203, 1402.0657

**Title: **Degenerate-shift equations in Liouville CFT

**Speaker: **Rongvoram Nivesvivat

**Date: **Wednesday 15 March 2023

**Time: **11:30-13:30 (Beijing time)

**Venue: **Ning Zhai W11

**Abstract: **

I will give a lightning discussion on the derivation of three-point functions in Liouville theory by using the degenerate fields and the crossing-symmetry equation. This approach was first proposed by J. Teschner in 1995 and can also be generalized to many other two-dimensional CFTs.

The talk will start from defining Liouville theory as CFT data: spectrum of primary fields and their three-point functions. Thereafter, I will explain how to obtain a set of functional equations for Liouville three-point functions by using the degenerate fields and the crossing-symmetry equation.

References: hep-th/9507109

**Title: **Non-invertible Global Symmetries in massless QED

**Speaker:** Xianjin Xie

**Date: **Wednesday 8 March 2023

**Time: **11:30-13:30 (Beijing time)

**Venue:** Ning Zhai W11

**Abstract: **

I will discuss how to construct non-invertible global symmetries in massless QED based on the paper by Choi, Lam, and Shao (2205.05086 see also 2205.06243). In this paper they show that the continuous, invertible U(1)_A axial symmetry is broken by the ABJ anomaly to a discrete, non-invertible global symmetry labeled by the rational numbers. Ref: 2205.05086, 2205.06243

**Title: **Generalize the FZZ duality

**Speaker:** Xiaoyi Shi

**Time: **15:10 -17:10 pm (Beijing time), Jan.6th(Friday), 2023

**Venue: **ONLINE Tencent(腾讯会议)：306-724-967

**Abstract: **

In this talk, I will explain some recent discussions about FZZ duality : 1. in 1603.05822 the authors proposed a more general identification between a normalizable mode of dilaton gravity and a mode of the tachyon with winding number one around the Euclidean time circle.

2. in 2208.00016 the authors checked a recently proposed duality of 2d CFTs, between the AdS3 sigma model with Kalb-Ramond flux and a free theory deformed by a winding condensate. I will introduce their proof of the equivalence of the two and three point functions on both sides.

**Title:** A proposal for 3d quantum gravity and its bulk factorization

**Speaker:** Xianjin Xie

**Time: **Fri.,15:10-17:10,Dec.2, 2022 (Beijing Time)

**Venue: **ONLINE, Zoom: 138 402 2750 Password: 951413

**Abstract: **

Xianjin will talk about 3D gravity and gravitational entanglement entropy. He will introduce the extended Hilbert space ideas and use it to propose a bulk factorization compatible with BTZ entropy base on the work 2210.14196v2.

Title: Stringy ER=EPR

Speaker: Xiaoyi Shi

Time: 11:30 am-1:30 pm (Beijing time), Nov.18th(Friday), 2022

Abstract: In the paper 2104.07233, the authors gave a worldsheet realization of ER=EPR as a duality between string theory in a connected, eternal black hole, and in a superposition of disconnected geometries in an entangled state. In the talk I will briefly illustrate their construction, including 1. review of FZZ duality 2.the formulation of string perturbation theory in the TFD and HH states 3.the Lorentzian string dualities, emphasizing the interpretation of the Euclidean winding operators

References: 2104.07233

Title: Berends-Giele recursion and Lie polynomials

Speaker: Yi-Xiao Tao

Time: 11:30 am-1:30 pm (Beijing time), Nov.11th(Friday), 2022

Abstract: In this talk, I will introduce Lie polynomial currents based on Berends-Giele recursion for bi-adjoint scalar tree amplitudes that take values in Lie polynomials.

References: 2012.00519

Title: Quantum Liouville theory

Speaker: Pengxiang Hao

Time: 11:30 am-1:30 pm (Beijing time), Nov.4th(Friday), 2022

Abstract: I will talk about the Liouville theory for itself, without referring to its origin. In particular, I will focus on the quantum aspect including the quantization, central charge, states, operators and correlation functions. A semi-classical picture will also be introduced.

References: hep-th/0402009, hep-th/9304011

Title: 2D gravity and random matrices

Speaker: Kangning Liu

Time: 11:30 am-1:30 pm (Beijing time), Oct. 28th(Friday), 2022

Abstract:I will talk about the triangulation approach to calculate 2D gravitational partition function, its relation with matrix model, and some techniques to solve matrix model partition function.

References: hep-th/9306153

Title: Matrix theory and membrane

Speaker: Zhengyuan Du

Time: 11:30 am-1:30 pm (Beijing time), Oct. 21st (Friday), 2022

Abstract:I will talk about the matrix theory action from the membrane action. Then I will talk about the M-theory object from matrix theory.

References: (1)hep-th:0002016(2)1708.00734

Title: Introduction to the BMS_3 symmetry

Speaker: Zehua Xiao

Time: 11:30 am-1:30 pm (Beijing time), Oct. 14th (Friday), 2022

Abstract: In this talk, I will briefly introduce the 3D Poincare algebra and the Poincare symmetry at positive null infinity. I will focus on the asymptotic Einstein Gravity in 3D, then introduce the BMS group. If time is enough, I will briefly introduce the flat limits techniques.

References: 1610.08526, 1508.00920, 1001.1541

Title: Introduction to the BFSS matrix theory

Speaker: Wenxin Lai

Time: 11:30 am-1:30 pm (Beijing time), Oct. 9th (Sunday), 2022

Abstract: In this talk, I will give a very brief introduction to the BFSS M(atrix) Theory and try to explore the motivation, evidence for this model as a first example of holographic duality. Refs: hep-th/9610043, hep-th/9510135

Title:Towards the non-perturbative cosmological bootstrap

Speaker: Reiko Liu

Time: 11:30 am-1:30 pm (Beijing time), Sep. 30th (Friday), 2022

Abstract: I'll talk about the properties of late-time correlators in dS spacetime, including the late-time expansion of bulk operators and the Källen-Lehmann spectral decomposition of two-point functions. Ref: 2107.13871

Title: Carrollian perspective on celestial CFT

Speaker: Xianjin Xie

Time: 11:30 am-1:30 pm (Beijing time), Sep. 16th (Friday), 2022

Abstract: The first goal is to show the same kinematic properties between 4d asymptotical spacetime and 3d sourced conformal Carrollian field theory(CCarrFT). Then show that the Ward identities of the sourced CCarrFT reproduce the BMS Ward identities of the celestial CFT after performing a certain integral transformations. Ref: 2202.04702