Thu, 27 Nov 2025
14:00
L4

Super-(conformal) monodromy defects

Andrea Conti (University of Oviedo)
Abstract
Recently, there has been an increasing interest in the study of defects in quantum field theories, with holography providing a powerful framework to explore various aspects of these super-(conformal) gauge theories.
In this talk, I will discuss supergravity solutions that are dual to codimension-2 superconformal monodromy defects. These solutions are obtained using gauged supergravities in D=4,5,6 and 7 dimensions. I will present a prescription to compute the defect entanglement entropy, outlining the renormalization procedure needed to regularise its divergencies, which I will discuss in detail. In some cases, we are also able to express this quantity in terms of the free energy/Weyl anomaly  and the conformal weight of the defect. In addition, we examine whether the defect entanglement entropy obeys a monotonicity theorem under RG flows.
If time allows, I will also discuss some new results for non-conformal monodromy defects.
Thu, 20 Nov 2025
14:00
L6

Renormalization from Unitarity

Clément Virally
Abstract

Renormalization group (RG) flow is a central aspect of our modern understanding of QFT. We may wonder about the relationship of renormalization to some of the other properties of a QFT, and if we can reconstruct RG flow from these properties. It has recently been proposed by Chavda, McLoughlin, Mizera and Staunton in [2510.25822] and [2511.10613] that unitarity can give us at least a part of RG flow, which is known as the Unitarity Flow Conjecture. In this talk, I will summarize the central ideas of this conjecture, and provide some evidence for it.

Thu, 13 Nov 2025
14:00
L4

Thermal correlators, QNMs and signatures of bulk black holes

Robin Karlsson
Abstract

I will discuss some of my work on thermal correlators in AdS/CFT. In particular, given a thermal correlator, how are the characteristic properties of bulk black holes encoded in such correlators? This includes exploring the spectrum of QNMs, the so-called thermal product formula, the photon ring, and geodesics bouncing off the black hole singularity. I will discuss how the latter might change when finite string effects are considered.

Thu, 06 Nov 2025
14:00
L4

Journal Club Cancelled

Abstract

There will be no journal club this week to avoid conflicting with FPUK.

Thu, 30 Oct 2025
14:00
L4

Sine dilaton gravity: wormholes, finite matrices and q-holography

Jacopo Papalini (Ghent University)
Abstract

I will discuss a two-dimensional dilaton gravity theory with a sine potential. At the disk level, this theory admits a microscopic holographic realization as the double-scaled SYK model. Remarkably, in the open channel canonical quantization of the theory, the momentum conjugate to the length of two-sided Cauchy slices becomes periodic. As a result, the ERB length in sine dilaton gravity is discretized upon gauging this symmetry. For closed Cauchy slices, a similar discretization occurs in the physical Hilbert space, corresponding to a discrete spectrum for the length of the necks of trumpet geometries. By appropriately gluing two such trumpets together, one can then construct a wormhole geometry in sine dilaton gravity, whose amplitude matches the spectral correlation functions of a one-cut matrix integral. This correspondence suggests that the theory provides a path integral formulation of q-deformed JT gravity, where the matrix size is large but finite. Finally, I will describe how this theory of gravity can be regarded as a realization of q-deformed holography and propose a possible implementation of this framework to study the near-horizon dynamics of near-extremal de Sitter black holes.

Thu, 23 Oct 2025
14:00
L4

Multifold Schwinger-Keldysh EFT -- what I understand and what I don't

Akash Jain
Abstract

The organisers asked me to give a brief talk on what I’ve been thinking about lately. So, I’ll tell you about Schwinger-Keldysh EFTs: an EFT framework for non-equilibrium dissipative systems such as hydrodynamics. These are built on a closed-time contour that runs forward and backward in time, allowing access to a variety of non-equilibrium observables. However, these EFTs fundamentally miss a wider class of observables, called out-of-time-ordered correlators (OTOCs), which are closely tied to quantum chaos. In this talk, I’ll share some thoughts on extending Schwinger-Keldysh EFTs to multifold contours that capture such observables. I’ll also touch on the discrete KMS symmetry of thermal systems, which generalises from Z_2 in the single-fold case to the dihedral group in the -fold case. With any luck, I’ll reach the point where I’m stuck and you can help me figure it out.

Thu, 16 Oct 2025
15:00
L6

Operator algebras meet (generalized) global symmetries

Andrea Antinucci
Abstract

Two different, almost orthogonal approaches to QFT are: (1) the study of von Neumann algebras of local observables in flat space, and (2) the study of extended and topological defects in general spacetime manifolds. While naively the two focus on different aspects, it has been recently pointed out that some of the axioms of approach (1) clash with certain expectations from approach (2). In this JC talk, I’ll give a brief introduction to both approaches and review the recent discussion in [2008.11748], [2503.20863], and [2509.03589], explaining (i) what the tensions are, (ii) a recent proposal to solve them, and (iii) why it can be useful.

Fri, 21 Nov 2025

12:00 - 13:15
L3

4D/3D QFT and representation theory

Tomoyuki Arakawa
(RIMS, Kyoto)
Abstract
4D/3D quantum field theory in theoretical physics is conceptually rich and gives rise to many interesting mathematical structures, even though a fully rigorous mathematical formulation of the theories themselves is still lacking. A relatively recent discovery by Beem et al. shows that to every 4D N=2 superconformal field theory one can associate a representation-theoretic object called a vertex algebra, which serves as an invariant (or observable) of the theory. Although vertex algebras are inherently algebraic, those arising as invariants of 4D QFT display striking connections with certain geometric objects that also appear as invariants of the same physical theories. Similarly, to each 3D N=4 gauge theory one can associate two vertex algebras—the A-twisted and B-twisted boundary VOAs—which may be viewed as refinements of the Higgs and Coulomb branches. In this talk, I will discuss some representation-theoretic aspects of these phenomena.
Short reachability networks
Groenland, C Johnston, T Radcliffe, J Scott, A Discrete Mathematics & Theoretical Computer Science
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