2026 SEUYC Theoretical Physics Seminars -- Upcoming

April 17th, 2026

Friday, 16:00-17:00

Sung-Soo Kim

 (University of Electronic Science and Technology of China)

Abstract

We present a novel viewpoint on S-folds of 5d superconformal field theories (SCFTs). The S-folding involves both a spatial quotient and an SL(2,Z) transformation on 5-branes in Type IIB string theory simultaneously. Focusing on the illustrative case of Z_2 S-folds, we analyze some physical observables and, in particular, construct the associated Seiberg-Witten curves. Our results reveal intriguing connections between the properties of these S-folds and recent developments in the understanding of orientifold planes, offering deeper insight into the role of discrete symmetries in 5d SCFTs.

April 24th, 2026

Friday, 16:00-17:00

Yang Lei (雷扬)

（Soochow University）

Abstract

Supersymmetric sectors of N=4 super-Yang-Mills theory motivate the study of the partition function for the counting of gauge-invariant functions of d=2,3 matrices transforming under the adjoint action of U(N). The partition function \mathcal{Z}_d(x) in the large N limit has a known Hagedorn phase transition at x=d^{−1} which provides a simple model for the phase structure of the thermal partition function of SYM. We study the all-orders asymptotic expansion of \mathcal{Z}_d(x) based on a geometric picture of concentric circles of poles in the complex plane accumulating in a natural boundary at ∣x∣=1. We find that the order by order structure has a precise combinatorial interpretation organized in terms of increasing cycle size of permutations arising in the enumeration of the invariants. We refer to this organization as small-cycle dominance, and find that it extends to refined versions of the partition functions depending on several complex variables. An analysis of the coefficients in the asymptotic expansion of \mathcal{Z}_d(x) using the modular property of the Dedekind eta function reveals that the asymptotic expansion is actually convergent for d≥d_crit=13.

May 8th, 2026

Friday, 16:00-17:00

Maximilian Schwick

(University of Bern)

Abstract

TBA

May 15th, 2026

Friday, 16:00-17:00

Jun Nian (年骏)

（University of Chinese Academy of Sciences）

Abstract

TBA

May 22nd, 2026

Friday, 16:00-17:00

Chen-Te Ma

(Great Bay University, Guangdong, China)

Abstract

TBA

May 29th, 2026

Friday, 16:00-17:00

Jan Albert

Abstract

TBA

June 12, 2026

Friday, 16:00-17:00

Guo Bin (郭斌)

Abstract

TBA

June 26, 2026

Friday, 16:00-17:00

Kiril Hristov

(Sofia University, Bulgaria)

Abstract

TBA

April 10th, 2026

Friday, 14:00-15:00

(Offline)

Yifan Chen (陈一帆)

(Shanghai Jiao Tong University)

Abstract

Ultralight bosons in the vicinity of compact objects can form gravitationally bound states, some of which undergo exponential growth by extracting rotational energy from black holes or through relaxation from ambient waves. These bound states can attain field amplitudes approaching the Planck scale, giving rise to phenomena analogous to those in early-universe cosmology and to observational signatures far stronger than those expected from local dark matter detection, ranging from electromagnetic features accessible through black hole imaging to gravitational wave imprints of the surrounding environment. In the case of accreting axion clouds, the field can accumulate into approximately spherical configurations with amplitudes near the decay constant, exhibiting either Bosenova collapse or saturation depending on the growth rate and axion mass. The resulting emission flux exhibits discrete spectral features determined by the axion potential, opening the possibility of probing ultraviolet axion models through terrestrial detection of these fluxes.

April 3rd, 2026

Friday, 16:00-17:00

David Berenstein

（University of California at Santa Barbara, USA）

Abstract

I will explain why studying the strong coupling expansion of large N QCD might be a viable way to address problems related to QCD dynamics. In particular, the strict large N strong coupling predicts that the dynamics is that of a gas of non-interacting loops, and that for each such (open) loop one can encode the state using word directions on how to go from a starting point to an end point. I will show that thinking this way naturally leads one to study some spin chain systems similar to those that arose in the study of N=4 SYM. Some subsectors of the spin chain are found to be integrable at the first order correction, but the most general sector is non-integrable. I will state some of the challenges ahead, particularly when it comes to better understanding the roughening transition. This is a transition one must go through before getting to the continuum limit.

March 27th, 2026

Friday, 16:00-17:00

Alejandro Cabo-Bizet

(University of Turin, Italy)

Why Indices Count the Total Number of Black Hole Microstates (at large N)

Slides_CaboBizet.pdf

Abstract

Understanding why Witten indices reproduce the exponential of the Bekenstein--Hawking entropy of supersymmetric black holes—despite counting bosonic and fermionic states with opposite signs—has remained a long-standing puzzle in string theory and gauge/gravity duality.

In this talk we will address this question in the canonical example of the duality between four-dimensional maximally supersymmetric Yang--Mills theory and ten-dimensional Type IIB supergravity/string theory. Concretely, we will explain why the superconformal index of this gauge theory, after averaging out oscillations, reproduces the semiclassical entropy of the dual supersymmetric black holes in the relevant asymptotic expansions. As a by-product, we will provide a microscopic interpretation of a non-linear constraint among charges that is well known to correspond, on the gravitational side of the duality, to the absence of naked CTCs in the Lorentzian black hole geometry.

Our results indicate that, rather than the superconformal index, the natural observable for counting black-hole microstates at finite $N$ is the Boltzmann partition function over BPS states. The talk will be based on 2512.19946 and on ongoing work.

March 20th, 2026

Friday, 16:00-17:00

Shuangyong Zhou

(University of Science and Technology of China)

Abstract

We propose a new method for constructing the consistent space of scattering amplitudes by parameterizing the imaginary parts of partial waves and utilizing dispersion relations, crossing symmetry, and full unitarity. Using this framework, we explicitly compute bounds on the leading couplings and examine the Regge behaviors of the constructed amplitudes. The method also readily accommodates spinning bound states, which we use to constrain glueball couplings. By incorporating dispersion relations, our approach inherently satisfies the Froissart-Martin/Jin-Martin bounds or softer high-energy behaviors by construction. This, in turn, allows us to formulate a new class of fractionally subtracted dispersion relations, through which we investigate the sensitivity of coupling bounds to the asymptotic growth rate.

March 13th, 2026

Friday, 16:00-17:00

（Postponed until further notice）

Arash Arabi Ardehali

(Institute for Research in Fundamental Sciences, Tehran, Iran)

Abstract

TBA

March 6th, 2026

Friday, 16:00-17:00

Marius de Leeuw

 (Trinity College Dublin, Ireland)

Abstract

Recently, there has been increased interest in anyonic chains. These are  spin chains whose excitations are given by objects in a fusion category. They have many interesting features, such as non-invertible symmetries and constrained Hilbert spaces. There are several examples of integrable anyonic chains, which is some cases lead to conformal field theories in the infinite volume limit. In this talk we introduce the concept of anyonic chains and explain how integrability is realized there. We will discuss recent results in relation to integrability and criticality of these models.

February 27th, 2026

Friday, 16:00-17:00

Elli Pomoni

(Humboldt University and DESY, Germany)

Hidden Symmetries of 4D N=2 Gauge Theories

Abstract

In this talk we will study the global symmetries of orbifolds of N = 4 Super-Yang-Mills theory and their marginal deformations. The process of orbifolding to obtain an N = 2 theory would appear to break the SU(4) R-symmetry down to SU(2)×U(1). We show that the broken generators can be recovered by moving beyond the Lie algebraic setting to that of a Lie algebroid. This remains true when marginally deforming away from the orbifold point by allowing the different gauge couplings to vary independently. The information about the marginal deformation is captured by a Drinfeld-type twist of this SU(4) Lie algebroid. The twist is read off from the F- and D- terms, and thus directly from the Lagrangian. We will show that the planar Lagrangian of the theory is invariant under this twisted version of the SU(4) algebroid and discuss implications of this hidden symmetry for the spectrum of the N = 2 theories.

January 23rd, 2026

Friday, 19:00-20:00

Pratik Rath

（University of California, Berkeley）

Abstract

Recently, Bousso and Penington (BP) made a proposal for the entanglement wedge associated to a gravitating bulk region. In this talk, I will derive this proposal in time-reflection symmetric settings using the gravitational path integral. To do this, we exploit the connection between random tensor networks (RTNs) and fixed-geometry states in gravity. By then expressing a general holographic state as a superposition over fixed-geometry states and using a diagonal approximation, we provide a general gravitational path integral derivation of the BP proposal. We demonstrate that the saddles computing the Rényi entropy depend on how the bulk region is gauge-invariantly specified. Nevertheless, we show that the BP proposal is universally reproduced in the n→1 limit.

January 13th, 2026

Friday, 16:00-17:00

Yunlong Zhang

(National Astronomical Observatories, CAS)

Abstract

In this talk, I will introduce several ultralight dark matter models based on modified gravity, along with their parameter constraints from astronomical observations. Topics include the cosmological constraints on apparent dark matter derived from the holographic FRW universe, the pulsar timing residuals induced by spin-2 ultralight dark matter in bimetric gravity, and the gravitational wave effects of axion-like dark matter in Chern–Simons modified gravity.

January 9th, 2026

Friday, 16:00-17:00

Li Li

(ITP, CAS)

Abstract

Understanding the nature of black holes remains a major frontier in modern science. While their external properties have been extensively studied, the internal structure and dynamics are essential to a complete understanding of their fundamental behavior. In this talk, I will present our recent progress on black hole interiors, with a particular focus on interior dynamics under higher-derivative corrections.