Soft theorems for the massless closed string and the hidden conformal symmetry of tree-amplitudes in pure Einstein gravity

by Dr Matin Mojaza (AEI, MPI Postdam-Golm)

Tuesday 18 Sept 2018, 14:00 → 15:30 Europe/Zurich

4/3-006 - TH Conference Room (CERN)

The aim of this seminar is to discuss the soft behavior of strings in scattering processes, their corresponding soft theorems, and the implications of those for string and field theory. In particular, I will explain how it is possible to extract the soft behavior of a massless string in the standard world-sheet formulation of string amplitudes. The well-known soft factorization theorems of gravitons can in this picture be explicitly established and allows us additionally to both understand string corrections as well as establish new soft theorems for the dilaton and the Kalb-Ramond B-field. A unified soft theorem for these three massless states will be offered and the extension to multiloops will be shown. Additionally parallels between the soft string-dilaton theorem and the soft theorem of the dilaton of spontaneously broken conformal invariance will be discussed, and a remarkable consequence of the string-dilaton theorem will be shown: That tree-level graviton amplitudes in pure field theory Einstein gravity must be invariant under special conformal transformations.