This week's ADS seminar this Thursday （19/12/2024）
Time: 1:30
Venue: Qiuzhen Hall, Ningzhai
Speaker: Ziqi Yan
Nordic Institute for Theoretical Physics (Nordita)
Title: AdS/CFT as a DLCQn/DLCQm Correspondence
Abstract: I will talk about the BPS nature of the decoupling limits that lead to matrix theories on D-branes, and their relations to the AdS/CFT correspondence. From this BPS perspective, I will then conjecture that a DLCQn/DLCQm correspondence, with m > n, captures the notion of holography in string theory. Here, DLCQ is short for Discrete Light Cone Quantization, which is a nonperturbative approach to quantum field theories and string/M-theory. Finally, I will show that the bulk geometry is generated via a deformation dual to the TTbar, which offsets the difference between the exponents n and m in the DLCQn/DLCQm correspondence.
This week's ADS seminar this Thursday （5/12/2024）
Time: 1:30
Venue: Qiuzhen Hall, Ningzhai
Speaker: Yunfeng Jiang (Southeastern University)
Title: Resurgence of TTbar-deformed Partition Function
Abstract: In this talk, I will discuss the torus partition function of TTbar-deformed conformal field theories. I will first review TTbar-deformation with an emphasis on the modular property of the deformed torus partition function. Then I will discuss how to compute the deformed partition function as a formal power series of the deformation parameter and introduce an efficient method to compute the coefficients. The large order perturbative data gives convincing evidence that the series is asymptotic. One can make sense of the asymptotic series and extract non-perturbative contributions from it by resurgence. Finally I will discuss the origin of the non-perturbative contribution, which comes from new complex saddle points after analytically continuing the modular parameters in the integral representation of the partition function.
This week's ADS seminar this Thursday （21/11/2024）
Time: 1:30
Venue: Qiuzhen Hall, Ningzhai
Speaker: Xingyang Yu（Virginia Tech）
Title: Top-down approach to generalized global symmetries
Abstract: I will review the recent progress in understanding generalized global symmetries, including the subtle categorical symmetries, from a string theory perspective. In particular, I will discuss how a (D+1)-dimensional symmetry theory is constructed when its associated D-dimensional QFT admits a string theory embedding. Under this construction, categorical symmetry operators are nicely built from topological sectors of various branes in string theory. Time permitting, I will provide examples of diverse dimensions and discuss several generalizations of symmetry theories from a top-down perspective.
ADS Seminar (14/11/2024) This Thursday!
Speaker: Yutai Zhang (Fudan)
Branes and Representations of DAHA of C^\vee C1
This talk will explore the representation theory of the spherical Double Affine Hecke Algebra (DAHA) of C^\vee C_1, using brane quantization. By examining the geometry of the Hitchin moduli space, I will demonstrate a one-to-one correspondence between finite-dimensional representations of the spherical DAHA and Lagrangian A-branes with compact support. Moreover, both finite- and infinite-dimensional representations can be naturally interpreted in terms of the D_4 root system. This talk is based on an ongoing work with Junkang Huang, Shutong Zhuang, and my supervisor, Satoshi Nawata.
Time: 1:30
Venue: Qiuzhen Hall, Ningzhai
ADS Seminar (24/10/2024) This Thursday as usual!
Speaker: Song He (ITP)
Correlators and amplitudes in N=4 super-Yang-Mills
I will report on new results on three closely-related quantities in N=4 super-Yang-Mills theory, the four-point half-BPS correlator, the (squared) scattering amplitudes and the energy correlators. The four-point correlator of half-BPS operators plays a crucial role in the study of AdS/CFT correspondence, scattering amplitudes and many other topics; it enjoys remarkable hidden symmetries and contains Wilson loops and scattering amplitudes in null limits. We find a new, universal behavior of the correlator dubbed “cusp limit”, which allows us to bootstrap its integrand（and corresponding four-gluon amplitudes) to 11 loops with various new structures. By taking n-gon null limit instead, we obtain new results for squared amplitudes at tree level, which contains the integrand of (leading order) energy correlators with n-3 detectors in the collinear limit; this provides new access to numeric and analytic results of energy correlators. All these are also encoded in a new geometric formulation of the four-point correlator, which naturally extends the geometry of (squared) amplituhedron.
Time: 1:30 pm
Venue: Qiuzhen Hall, Ningzhai
This week's ADS seminar is ONLINE (see zoom link below)
It's scheduled on **Friday 18th of October 10am**
Speaker: Christian Ferko (Northeastern U)
Title: TT Deformations of Yang-Mills Theories
Abstract: In this talk, I will discuss classical deformations of non-Abelian gauge theories which are driven by functions of the energy-momentum tensor, and which are inspired by Zamolodchikov's TTbar operator in two dimensions. Although finding the full solutions to these flow equations is difficult, one can nonetheless make progress by restricting to special field configurations such as instantons and monopoles. I will also describe a modification of these stress tensor flows, called the "symmetrized single trace TT deformation", which -- when applied to a Yang-Mills seed theory -- produces Tseytlin's symmetrized trace prescription for non-Abelian Born-Infeld theory.
Join Zoom Meeting
https://us02web.zoom.us/j/83038303787?pwd=FRvKhwgoJL6mDwsAAxwnxKroe5eHrd.1
Meeting ID: 830 3830 3787 Passcode: 423200
10/10 ADS seminar (THIS THURSDAY)
Speaker: Yidun Wan (Fudan University)
Title: Noninvertible Gauge Symmetry in (2+1)d Topological Orders: A String-Net Model Realization
We develop a systematic framework for understanding symmetries in topo-logical phases in 2 + 1 dimensions using the string-net model, encompassing both gauge symmetries that preserve anyon species and global symmetries permuting anyon species,including both invertible symmetries describable by groups and noninvertible symmetries described by categories. As an archetypal example, we reveal the first noninvertible categorical gauge symmetry of topological orders in 2 + 1 dimensions: the Fibonacci gauge symmetry of the doubled Fibonacci topological order, described by the Fibonacci fusion 2-category. Our approach involves two steps: first, establishing duality between different string-net models with Morita equivalent input fusion categories that describe the same topological order; and second, constructing symmetry transformations within the same string-net model when the dual models have isomorphic input fusion categories, achieved by composing duality maps with isomorphisms of degrees of freedom between the dual models. If time permits, I will also talk about a subsequent work on anyon condensation.
Time：10/10/2024 1:30 pm Qiuzhen Hall, Ningzhai
9/26 ADS Seminar:
Speaker: Jing-Yuan Chen （IASTU）
Title: Instanton in Lattice QCD from Higher Category Theory
Abstract: A long standing problem in lattice QCD is to find a natural definition of instanton operator on the lattice. I will show how this problem is -- and has to be -- solved by higher category theory. In this language, the solution is a deep generalization of the Villain model familiar in condensed matter physics and in lattice Maxwell. Using the particular categorical structure, one can define 2d Wess-Zumino-Witten term, 3d skrymion and 4d hedgehog in lattice S^3 (pion) non-linear sigma model, and 3d Chern-Simons term, 4d instanton and 5d Yang monopole in lattice Yang-Mills.
In a larger scope, I will sketch a systematic program towards rethinking the relation between continuum QFT and lattice QFT. As a result, all topological operators can be naturally defined on the lattice. I will discuss what implications this might have on the understanding of renormalization, the relation between dynamical and topological QFT (in particular, going beyond the well-developed tensor category formalism which only deals with discrete degrees of freedom, and find a unifying language that emcompases the more physical continuous degrees of freedom), and the program of constructive QFT.
Time：26/09/2024 1:30 pm Qiuzhen Hall, Ningzhai
ADS seminar this coming Thursday
Speaker : Wei Wang (TD Lee Institute, Jiaotong University)
Title: Building holographic code from the boundary.
Abstract: Holographic quantum error-correcting code, the quantum-information structure hypothesized for the AdS/CFT correspondence, has being attracting increasing attention in new directions interrelating the studies of quantum gravity and quantum simulation. In this work, we initiate a novel approach for building holographic code that can be generally applied in potentially broad and interdisciplinary contexts. Our approach takes an “opposite” route to the conventional paradigm that is based on bulk tensor-networks. As illustrated in an exact model, we start from scalable descriptions of boundary qudits which can guide succinct quantum-circuit simulations, and rigorously show how the bulk qudits and the encoding structure emerge from boundary entanglement patterns. By investigating the entanglement patterns, we systematically unfold the hypothetical structure for bulk reconstruction and the details of the Ryu-Takayanagi formula in the formalism of operator-algebra quantum error correction, demonstrating desired properties that are not yet proved in the established models. Our work might offer a fresh perspective for the study of holographic code.
Bio: Wei Wang obtained his Ph.D. in Physics from University of Oklahoma (U.S.) in 2017. Then he worked as a postdoc in Max Planck Institute for the Physics of Complex Systems (Germany). Now he is an independent postdoc in Tsung-Dao Lee Institute, Shanghai Jiao Tong university. His current work primarily focuses on interdisciplinary research at the intersection of quantum information, condensed matter physics, and high-energy physics.
Time: Thur., 13:30-15:05, Sept. 19, 2024 (THIS THURSDAY)
Venue: Qiuzhen Hall, Ningzhai (Inside Tsinghua main campus)
(please contact us if you need help getting into campus)
