Joint hep-th seminars with ULB, VUB, KUL and UGent

On the 8th of November UMONS will host the Belgian joint theoretical high-energy physics seminars organised by the Service de Physique de l’Univers, Champs et Gravitation of UMONS, the Service de Physique Théorique and the Service de Physique Théorique et Mathématique, both of the ULB, the Theoretical Particle Physics Group of the VUB, the High Energy Physics and Relativistic Field Theory group of the KUL, the Theoretical High Energy Physics group of the UGent and the International Solvay Institutes.

The speakers will be Blagoje Oblak (ULB Brussels), Antoine Bourget (IPhT, Saclay and LPENS, Paris) and Ana-Maria Raclariu (Amsterdam U.):

10h30, room Mirzakhani, building De Vinci: Blagoje Oblak

Anisotropic Quantum Hall Droplets

This talk is devoted to 2D droplets of free electrons in a strong magnetic field, placed in an arbitrary confining potential. I show that semiclassical methods in the lowest Landau level yield near-Gaussian energy eigenstates localized on level curves of the potential, implying explicit formulas for local many-body observables in the thermodynamic limit. In particular, correlations along a droplet’s edge are long-ranged, in accordance with the 1D chiral conformal field theory description of low-energy dynamics. This notably involves inhomogeneous correlations and position-dependent guiding centre velocities, but still results in a homogeneous theory thanks to remarkable cancellations between the radial and angular dependencies of eigenfunctions. Finally, I describe realistic microwave absorption experiments that probe the detailed shape of a droplet without resorting to local imaging.

12h00, room Mirzakhani, building De Vinci: Antoine Bourget

Why Symplectic Singularities?

In the past decade, a kind of geometric space known as symplectic singularities have become a popular topic for an increasing community of physicists and mathematicians. My goal in this presentation is to explain to you the reasons for this sudden interest, and try to convey the delicate beauty of this field.
Within the context of supersymmetric theories, they have incarnations as hyperKähler quotients, Higgs branches, Coulomb branches, they serve as a tool in the study of SCFTs, allow to explore RG flows and deformations, and are connected to vertex operator algebras. In this review talk, I will recall the basic definitions and examples, and mention a few very recent advances and open problems.

14h30, room Vésale 30, building Vésale: Ana-Maria Raclariu

Entanglement, soft modes and celestial CFT

In this talk I will revisit the calculation of entanglement entropy in free Maxwell theory in 4-dimensional Minkowski spacetime. Weyl invariance allows for this theory to be embedded inside the Einstein static universe. Future null infinity can be regarded as the union of Cauchy slices inside the future Milne patches (denoted L and R) of two Minkowski geometries related by a conformal inversion. I will show that the Maxwell vacuum state decomposes as the thermofield double state of conformal primary modes supported inside the L and R patches and related by a conformal inversion. I will comment on the relation between inversions and shadow transforms. I will conclude by discussing the soft sectors associated with the two patches. In particular, I will demonstrate that conformally soft mode configurations at the entangling surface, or equivalently correlated fluctuations in the large gauge charges of the two Milne patches, give a non-trivial contribution to the entanglement entropy across a cut of future null infinity.