T. D. Brennan
Title: Anomalies of Discrete 1-Form Symmetries in QCD-like Theories
Abstract: In this talk we will discuss a new class of non-perturbative anomalies of discrete 1-form global symmetries in 4D QCD-like theories. This generalizes the techniques developed by Wang-Wen-Witten to more general theories that allow for discrete 1-form global symmetries including chiral gauge theories. We will demonstrate several new anomalies and comment on their implication on symmetric mass generation in 3+1D.

Marialuisa Frau
Title: Strong coupling results in N=2 gauge theories
Abstract: We will discuss recent developments in the study of correlation functions of chiral scalar operators and Wilson loops in four-dimensional N=2 quiver gauge theories. Using supersymmetric localization, it is possible to map the computation of these correlators to an interacting matrix model and obtain expressions that are valid for any value of the ’t Hooft coupling in the planar limit of the theory. In particular, we will focus on the strong-coupling regime, where these expressions allow us to compute the leading and subleading orders behavior of the observables in an analytic way.

Elizabeth Helfenberger
Title: Line defects in fermionic CFTs
Abstract: In this talk I will discuss line defects in the fermionic CFTs in the Gross-Neveu-Yukawa universality class in dimensions $2<d<4$. These CFTs may be described as the IR fixed points of the Gross-Neveu-Yukawa (GNY) model in $d=4-\epsilon$, or as the UV fixed points of the Gross-Neveu (GN) model, which can be studied using the large $N$ expansion in $2<d<4$. These models admit natural line defects obtained by integrating over a line either the scalar field in the GNY description, or the fermion bilinear operator in the GN description. We compute the beta function for the defect RG flow using both the epsilon expansion and the large $N$ approach, and find IR stable fixed points for the defect coupling, thus providing evidence for a non-trivial IR DCFT. We also compute some of the DCFT observables at the fixed point, and check that the $g$-function associated with the circular defect is consistent with the $g$-theorem for the defect RG flow.

Anatoly Konechny
Title: RG boundaries and Cardy's variational ansatz for multiple perturbations
Abstract:   We will consider perturbations of 2D CFTs by multiple relevant operators. The massive phases of such perturbations can be labeled by conformal boundary conditions. Cardy's variational ansatz approximates the vacuum state of the perturbed theory by a smeared conformal boundary state. In this talk we will discuss the limitations and propose generalisations of this ansatz using both analytic and numerical insights based on TCSA. In particular we analyse the stability of Cardy's ansatz states with respect to boundary relevant perturbations using  bulk-boundary OPE coefficients. We show that certain transitions  between the massive phases arise from a pair of boundary RG flows.  The RG flows start from the conformal boundary on the transition surface and end on those that lie on the two sides of it. As an example we work out the details of the phase diagram for the Ising field theory and for the tricritical Ising model  perturbed by the leading thermal and magnetic fields. Based on arXiv:2306.13719.

Francois Parisen Toldin
Title: Advances in the boundary O(N) universality class
Abstract: In critical phenomena, the presence of surfaces or more general boundaries gives rise to rich phase diagrams and interesting phenomena, such as critical adsorption and critical Casimir forces. Despite being a mature subject, boundary critical phenomena have recently attracted a renewed attention, driven in particular by the discovery of unexpected behavior in various quantum spin models, and by progresses in conformal field theory. In this context, a reexamination of the simplest model of boundary criticality -- the three-dimensional O(N) model bounded by a bidimensional surface -- has led to the discovery of a hitherto overlooked boundary phase, the so-called extraordinary-log phase. In this seminar I will review these recent advances, focusing in particular on results of numerical simulations, and discuss future research directions.

Ingo Runkel
Title: Non-invertible symmetries and their gaugings in low-dimensional field theory
Abstract: The study of topological defects in quantum field theory has seen a wealth of activity recently leading to many interesting insights, for example the explicit realisation of non-invertible topological defects in higher dimensional QFTs via the gauging of higher form symmetries.  In this talk, I would like to focus on two-dimensional examples, where such defects and their properties have been investigated for some time already. I would like to show some of the structural insights into 2d CFT one can gain from topological defects and from their gauging. In this way, the well-understood two-dimensional case might serves as a source of ideas and as a test-case for higher dimensional constructions.

Jorge Russo
Title: Defects in Scalar Field Theories

Erik Tonni
Title: Entanglement entropies for Lifshitz fermionic fields at finite density
Abstract: The entanglement entropies of an interval for the free fermionic spinless Schroedinger field theory at finite density and zero temperature are investigated. The interval is either on the line or at the beginning of the half line, when either Neumann or Dirichlet boundary conditions are imposed at the origin. We show that the entanglement entropies are finite functions of a dimensionless parameter proportional to the area of the rectangular region in the phase space identified by the Fermi momentum and the length of the interval. For the interval on the line, the entanglement entropy is a monotonically increasing function. Instead, for the interval on the half line, it displays an oscillatory behaviour related to the Friedel oscillations of the mean particle density at the entangling point. By employing the properties of the prolate spheroidal wave functions or the expansions of the tau functions of the kernels occurring in the spectral problems, determined by the two point function, we find analytic expressions for the expansions of the entanglement entropies in the asymptotic regimes of small and large area of the rectangular phase space region. Extending our analysis to a class of free fermionic Lifshitz models, we find that the parity of the Lifshitz exponent determines the properties of the bipartite entanglement. 

Arkady Tseytlin
Title: Wilson Loop at large N and quantum M2-brane
Abstract: I will review recent work with Simone Giombi in 2303.15207 on reproducing  the localization prediction for the prefactor in the expectation  value of 1/2 BPS   Wilson loop in 3d ABJM theory   from 1-loop  computation in supermembrane theory in AdS4 x S7/Z_k   background. I will also mention some  generalizations.