2024年东南大学丘成桐中心数学物理青年学者论坛

On behalf of Shing-Tung Yau Center and School of Physics, Southeast University, we are pleased to announce Forum for Young Scholars in Mathematical Physics at the end of 2024. The purpose of this forum is to promote interaction among young theoretical physicists, and to give participants an opportunity to get to know our Center at the center of Nanjing city, China. We also encourage participants to apply for faculty positions, including tenured and tenure-track positions, in our center.

Most of the forum is broadcasted by Zoom, according to China Standard Time (UTC+8). The details are:

• URL: https://us02web.zoom.us/j/3854420225?pwd=SXY4eWJKOTBFZWJDaE16aXpTamY1QT09

• Meeting ID: 385 442 0225

• Passcode: yauc

Schedule

Day 1: December 28 (Saturday)

Day 2: December 29 (Sunday)

The duration of each talk is 40 minutes plus 5 minutes for questions. Offline speakers are marked by *.

Abstract

[Sunjin Choi] Black hole cohomologies at finite N
We study new cohomologies for the local BPS operators of the maximal super-Yang-Mills theory with SU(2), SU(3), and SU(4) gauge groups to better understand the black hole microstates. We first analyze the index of these black hole operators and explicitly construct their cohomologies to study how they imitate the quantum black holes. We find many towers of states and partial no-hair behaviors where certain gravtions are forbidden to dress these black hole operators. This qualitatively agrees with the behavior of the perturbative hairy BPS black holes. Throughout this talk, we mainly focus on a subsector of the field theory corresponding to the BMN matrix theory, which exhibits a black hole-like entropy growth at large N.

[Xi Tong] There and Back Again: Mapping and Factorising Cosmological Observables
Observables in cosmology consist of correlation functions of various cosmological fields. These correlators encode invaluable information about the wavefunction that characterizes the state of the primordial universe. In this talk I will present a simple yet novel duality between correlators and wavefunction coefficients. The duality manifests itself as a non-perturbative Z4 symmetry in the dictionary of correlators and the modulus parts of wavefunction coefficients, and maps any equation in the dictionary involving the two to another equation in the dictionary. To demonstrate the power of the duality already at tree-level, we derive a correlator-to-correlator factorisation formula for the parity-odd part of cosmological correlators which relates n-point observables to lower-point ones via a series of diagrammatic cuts. These relations are in principle testable as they involve observables defined for arbitrary physical kinematics (i.e. without any analytic continuation). For n = 4, the factorization formula provides a relation between the parity-odd curvature trispectrum and the mixed bispectra involving two curvature modes and an additional light state.

[Manki Kim]String perturbation theory of Klebanov-Strassler throat

In this talk, I will explain how to study string perturbation theory of the Klebanov-Strassler solution in the large radius approximation based on open-closed superstring field theory. Combining the large radius expansion and a double scaling limit, we find a perturbative background solution of open-closed superstring field theory that corresponds to the Klebanov-Strassler solution. To illustrate the utilities of this approach, we break supersymmetry of the background by placing a stack of anti-D3-branes at the tip of the throat. We then find a perturbative open string background solution to the third order in the large radius approximation, which agrees with the well-known supergravity analysis of Kachru-Pearson-Verlinde (KPV) on the stability of the anti- D3-brane supersymmetry breaking. The perturbative background solution to the open string field theory we found is expected to be dual to an NS5-brane probing the KS solution.

[Hao Zhang] Atomic Higgsing of 6D SCFTs
In this talk, we present a procedure to characterize a full Higgs branch Hasse diagram for any given 6d N=(1,0) SCFT constructed via F-theory. This can be done by a procedure of determining all the atomic (i.e., minimal) Higgsings on the generalized quiver description on the tensor branch of the 6d SCFT. We call this procedure the atomic Higgsing and we explain how to implement it iteratively. We present our general algorithms with many concrete examples of Hasse diagrams. We also compare our algorithm with the Higgsings determined by the 3d N=4 magnetic quivers. For the cases where the magnetic quivers are unitary, we can reproduce the full Hasse diagrams. We also construct the orthosymplectic magnetic quivers from the Type IIA brane systems for some new examples. Our approach, based on F-theory, applies to the known and new orthosymplectic cases, as well as theories that do not have known descriptions in terms of magnetic quivers. We expect our geometry-based approach to help extend the horizon of the RG flows of the 6d SCFTs.

[Ho Tat Lam] Global Aspects of Exactly Marginal Current-Current Deformations

Conformal field theories connected by exactly marginal deformations form conformal manifolds. In two dimensions, a large class of conformal manifolds is generated by bilinear composites of currents, known as current-current deformations. In this talk, we will revisit these deformations and prove that a dense set of points on the conformal manifolds are related to the seed theory through discrete gauging. This perspective allows us to connect the topology of the conformal manifolds with the anomalies of the currents. We will also discuss how current-current deformation can be understood from the recently proposed continuous abelian symmetry topological field theory.

This talk is based on work in progress.

[Zixia Wei] Localized Black Holes in AdS3: Thermodynamics and Entanglement Entropy
A holographic conformal field theory (CFT) is a CFT whose low-energy behavior can be described by Einstein gravity in anti-de Sitter spacetime (AdS) with one higher dimension. For a 2D holographic CFT, modular invariance largely determines the spectrum at both low and high energies, leaving only the medium-energy range undetermined. In the corresponding 3D AdS, this implies that the low-energy statistics is described by global AdS plus matter, while the high-energy statistics is described by the BTZ black hole, independent of the details of the underlying 2D CFT. The specific details of the spectrum are only reflected in the configurations within the medium- energy range. In this talk, we present a class of non-supersymmetric localized black holes in Type IIB supergravity in AdS3 ×S3×T4, which is dual to a 2D CFT (the D1-D5 CFT) in the strong coupling limit. We first study the thermodynamics of these localized black holes and observe that they dominate over the BTZ black hole and thermal AdS in the medium-energy range left undetermined by the modular bootstrap. These solutions provide a path to analytically study the energy window constrained by modular invariance in AdS3 /CFT2 . As an example, we compute the holographic entanglement entropy associated with these solutions and discuss some intriguing physics in the medium-energy range.

[Yao Ma] Regions in Asymptotic Expansions of Amplitudes
The method of regions, a systematic approach to the asymptotic expansions of Feynman integrals, suggests that a Feynman integral can be reconstructed by summing over integrals expanded in certain regions. This technique not only facilitates the computation of Feynman integrals but also provides valuable insights for formulating an EFT, such as the Soft-Collinear Effective Theory (SCET).
However, a fundamental question remains unanswered for most cases: how does one systematically determine the complete list of regions?
This talk aims to address this question to all orders by drawing from some recent research works. This talk addresses this question to all orders, drawing from recent research. The results presented focus on generic massless scattering, with potential generalization to massive cases. Additionally, these findings have important implications for other topics, including infrared subtraction, factorization breaking, and Landau singularities, which will be discussed during the presentation.

[Yuezhou Li] Causality constraints on effective field theories
We will review the bootstrap method for constraining low-energy effective field theories (EFT) using causality and unitarity. This method provides a systematic approach to sharpening our understanding of a variety of EFTs. Our focus will be on applying this bootstrap method to sharply constrain the polynomial modified gravity as gravitational EFTs, where we show that the Wilson coefficients are rigorously bounded uniformly by the Newton constant and the scale of new physics or the mass of higher-spin states. Such bounds can be uplifted to Anti-de Sitter space, providing sharp constraints on holographic conformal field theories. By coupling gravitons to a large number of matter fields, we also clarify what happens to the universal scale at which gravitational field theories break down and signals the necessity of an underlying non-field-theoretic description of gravity, which we refer to as the high-spin onset.

[Han Ma] Z2 spin liquids in the Higher spin Kitaev Honeycomb model: an exact Z2 gauge structure in a non-integrable model
The higher spin Kitaev models have extensive locally conserved quantities the same as the spin-1/2 Kitaev honeycomb model, although they are not exactly solvable. In this talk, I will present their exact gauge structure by introducing a Majorana parton construction for a general spin-S. These conserved quantities are exactly the Z2 gauge fluxes. Particularly, we find an even-odd effect that the Z2 gauge charges are fermions in the half integer spin model, but are bosons in the integer spin model. We further prove that the fermionic Z2 gauge charges are always deconfined; hence, the half integer spin Kitaev model would have nontrivial spin liquid ground states regardless of interaction strengths in the Hamiltonian. The bosonic Z2 gauge charges of the integer spin model could condense, leading to a trivial product state, and this is indeed the case at the anisotropic limit of the model.

[Yijian Zou] Mixed-state phases and quantum error correction
Quantum phases of matter are characterized by patterns of long-range entanglement. In recent years, it has been demonstrated that mixed states can exhibit a rich phase diagram that goes beyond pure states. I will overview the study of mixed-state phases and emphasize its connection with quantum error correction codes. We give a precise definition of mixed-state phases using local channel transformations. We define renormalization group (RG) transformations on mixed states which establish the phase equivalence. We study the RG in several examples and show that they are related to error correctability in quantum error correction codes.

[Zhenghao Zhong] A Radioactive Higgs Mechanism
The Higgs mechanism is a well known process in quantum field theory where scalar fields gain VEVs and gauge groups are broken to subgroups. Today, I will talk about the Higgs mechanism in superconformal field theories (SCFTs) with eight supercharges. Due to a lack of Lagrangian description in much of the SCFTs in the literature, Higgsing is not easy. Using magnetic quivers, we introduce a new algorithm called Decay and Fission which performs Higgs mechanism for SCFTs regardless whether it has a Lagrangian description. I will demonstrate this with various examples in spacetime dimensions d=4,5,6. Finally, I will use the algorithm to arrive at a bound on the landscape of 3d mirror pairs that have quiver gauge theory descriptions.

Registration

This forum is open to all young theoretical physicists, and no registration is needed.

Organizers

Please contact Qiang Wen or Ryo Suzuki for any queries regarding this forum. We hope you will join us for this exciting event.