ITMP Seminar "Even photons break de Sitter symmetry"

Dear Colleagues,
We are pleased to announce that the next ITMP seminar will be held on Wednesday, December 11, 18:00 (Moscow time). It will be organised via Zoom.

Speaker: Dr Dražen Glavan, Institute of Physics (FZU), Prague

Title: Even photons break de Sitter symmetry

Abstract: It is commonly held that the propagator for the massless vector field in de Sitter in the general covariant gauge has to respect all the symmetries of the maximally symmetric background. However, this is precluded by the Ward-Takahashi identity that has gone unnoticed thus far. I will present the construction of the photon propagator that satisfies all the conditions of a consistently quantized theory, and that maintains all de Sitter symmetries except spatial special conformal transformations. This propagator vanishes in the infrared, opposed to previously reported solutions to just the propagator equation of motion. Even though the de Sitter breaking pertains to the gauge sector, it is important when interactions are considered. I will discuss the energy-momentum tensor as the simplest one-loop observable to demonstrate further problems arising from failing to account for the Ward-Takahashi identity and the de Sitter breaking it requires.