Title: [NCTS-NTU String Theory Seminar] Soft factors in the presence of small negative cosmological constant
Speaker: Dr. Arpita Mitra (Physics Division, National Center for Theoretical Sciences)
Time: May 6, 2022 (Fri) 14:30-15:30
Venue: RM815, Dept. of Physics, NTU

Abstract:
In asymptotically non-flat backgrounds, the usual flat spacetime S-matrix description can not be used to describe scattering since massless asymptotic states are not free. However, the gauge invariance remains intact even for asymptotically non-flat theories implying an analog of soft theorems to be valid in this case as well. We computed a soft factor from the classical scattering profile of a probe particle on the AdS black hole spacetime in the small cosmological constant (Λ) limit. This required defining a double scaling soft limit – where the frequency of the radiation vanishes, as the AdS radius tends to infinity faster. Our result provides an additional perturbative correction linear in Λ to the flat spacetime soft factors result around the center of AdS spacetimes. We proposed a linear in Λ corrected Ward identity, following the known equivalence between large gauge Ward identities and soft photon theorems in asymptotically flat spacetimes.