University of Crete HEP Seminars


FP7

Towards solving CFTs with artificial intelligence

Speaker: Costis Papageorgakis
Institution: Queen Mary University London
Time: Tuesday 28 September 2021, 13:00
Venue: Webinar
Abstract: I will introduce a novel numerical approach for solving the conformal-bootstrap equations with Reinforcement Learning. I will apply this to the case of two-dimensional CFTs, successfully identifying well-known theories like the 2D Ising model and the 2D CFT of a compactified scalar, but the method can be used to study arbitrary (unitary or non-unitary) CFTs in any spacetime dimension.
Recording: The recorded talk can be found here.

Revisiting Coleman-de Luccia transisitions in the AdS regime using holography

Speaker: Elias Kiritsis
Institution: University of Crete and APC, Paris
Time: Tuesday 05 October 2021, 13:00
Venue: Webinar
Abstract: Coleman-de Luccia processes for AdS to AdS decays in Einstein-scalar theories are studied. Such tunnelling processes are interpreted as vev-driven holographic RG flows of a quantum field theory on de Sitter space-time. These flows do not exist for generic scalar potentials, which is the holographic formulation of the fact that gravity can act to stabilise false AdS vacua. The existence of Coleman-de Luccia tunnelling solutions in a potential with a false AdS vacuum is found to be tied to the existence of exotic RG flows in the same potential. Such flows are solutions where the flow skips possible fixed points or reverses direction in the coupling. This connection is employed to construct explicit potentials that admit Coleman-de Luccia instantons in AdS and to study the associated tunnelling solutions. Thin-walled instantons are observed to correspond to dual field theories with a parametrically large value of the dimension ∆ for the operator dual to the scalar field, casting doubt on the attainability of this regime in holography. From the boundary perspective, maximally symmetric instantons describe the probability of symmetry breaking of the dual QFT in de Sitter. It is argued that, even when such instantons exist, they do not imply an instability of the same theory on flat space or on R × S3^{3}3.
Recording: The recorded talk can be found here.