Line defects in CFTs: RG flows, cusps, and applications

• Gabriel Cuomo (New York U., CCPP and Princeton U.)

Line defects describe one-dimensional probes of a quantum field theory. Physically interesting examples can be found in different systems, ranging from magnets to gauge theories. In this talk, I will discuss some general properties of line defects, including the monotonicity of the defect renormalization group flow and the structure of the cusp anomalous dimension. I will illustrate the general results by discussing the magnetic line defect in the O(N) CFT. If time permits I will mention additional examples.

Bootstrapping the half-BPS line defect CFT in N=4 SYM

• Carlo Meneghelli (University of Parma)

Half-BPS Wilson lines in N=4 super Yang-Mills provide an interesting and well studied class of 1d CFTs. In this talk, I will present how this 1d CFT can be solved, in the planar limit, in a perturbative expansion around strong coupling using analytic bootstrap methods. The talk is based on joint work with Pietro Ferrero.

Defects in quantum systems: symmetry, entanglement, and teleportation

• Sara Murciano (Caltech)

In this talk, I will explore the significant role of defects in various aspects of quantum systems. First, I will discuss how global symmetries can be embedded in topological defects and their connection to symmetry-resolved entanglement. Next, I will examine the influence of conformal junctions on various entanglement measures, highlighting how these insertions can affect quantum correlations. Finally, I will delve into the realm of weak measurements of critical wavefunctions, emphasizing their interplay with defect lines. As a concrete example, I will demonstrate how defects can disrupt a quantum teleportation protocol, preventing Alice from successfully transmitting her state to Bob. Through these discussions, I plan to shed light on the connections between defects and fundamental quantum phenomena.

Universal Bounds in interface conformal field theories

• Andreas Karch (U. Texas, Austin)

Critical phenomena in the presence of interfaces provide a much richer arena than their more studied cousin of boundary critical phenomena. In this talk, I'll review certain observables that are new and unique in interface conformal field theory and then demonstrate some novel bounds we can derive on these quantities using techniques from holography and quantum information.

Energy transport in 2D holographic interfaces

• Giuseppe Policastro (Ecole Normale Superieure)

Universal properties of two-dimensional conformal interfaces are encoded in the flux of energy transmitted and reflected for an excitation scattering with the interface. I will discuss the computation of this scattering process in the minimal holographic model of a brane in AdS3, and extended brane configurations that can mimic top-down smooth gravity solutions. The talk is based on work in collaboration with C. Bachas, S. Bagueira, S. Chapman, D. Ge and T. Schwarzman.

Topological disorder operators

• Meng Cheng (Yale University)

Solving conformal defect using the fuzzy sphere regularization

• Yin-Chen He (Perimeter Institute)

In this talk, I will introduce our recently proposed fuzzy sphere regularization of 3D CFTs and talk about its application to the conformal defect. Specifically, I will use the pinning field defect of 3D Ising as an example to demonstrate the versatility of fuzzy sphere regularization in the study of defect, including the computation of operator spectrum, bulk-defect OPE and g-function.

CFT1/QFT2: massless scattering and bulk RG flows

• Miguel Paulos (ENS)

In this talk we discuss how it is possible to study QFTs in AdS2 (or 2d BCFTs), and in particular their flat space limit, by accurately bootstrapping 1d CFTs. We also show how combining crossing with locality allows one not only to reconstruct bulk scattering but also local operators and their correlation functions at all scales, and recover their flat space form. We discuss the physical meaning of these results, their limitations, and their relation to bounds on CFT/QFT data. Along the way we explain how both the 1d (single correlator) crossing equation and the associated bulk operator reconstruction problem are now essentially solved.

Boundary critical behavior of the 3D O(N) model

• Francesco Parisen Toldin (Aachen University)

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. Beyond surfaces, other kind of extended defects, such as line defects, have been considered. In this seminar I will give an introduction to the problem and review the recent advances, focusing in particular on results of numerical simulations, and discuss future research directions.