Joint Theory Seminar: Andrea Puhm

Title: Asymptotic symmetries from logarithmic soft theorems

Abstract: Over the past decade significant progress has been made towards tackling the challenging question: What are the symmetries of Nature? Key to this has been the realization that gravity in the infrared manifests itself in seemingly different yet equivalent ways known as asymptotic symmetries, soft theorems, and memory effects, and these developments form the foundation towards formulating a holographic principle for quantum gravity in our world. In turn the recent progress in the emergent field of ``celestial holography'' has shed light on the amount  of symmetries. Gauge theories and perturbative gravity in four dimensions turn out to be governed by a tower of infinite-dimensional symmetries that arise from tree-level soft factorization theorems of the S-matrix involving low-energy ("soft") massless particles. However, aside from the leading soft theorems which are all-loop exact, subleading ones receive loop corrections due to long-range infrared effects which result in new soft theorems with logarithmic dependence on the energy of the soft particle. In this talk I will initiate a program to compute long-range infrared corrections to the generators of asymptotic symmetries and provide a symmetry interpretation for the leading logarithmic soft theorems. By virtue of being universal and all-loop exact, this is a key element for a holographic principle in spacetimes with flat asymptotics.

Student session: 13:10