Perturbative corrections to soft photon theorems for massless scalar QED in de Sitter spacetime

TL;DR

This paper derives perturbative corrections to soft photon theorems for massless scalar fields in de Sitter spacetime, resolving previous ambiguities and confirming the universality of the results at tree level.

Contribution

It provides a consistent framework for computing soft photon corrections for massless scalars in de Sitter, extending previous work to the massless limit.

Findings

Results are consistent with previous massive scalar corrections in the massless limit.

Framework applies to tree-level scattering of massless scalars with soft photon emission.

Comments on the universality of soft photon corrections in de Sitter spacetime.

Abstract

The perturbative corrections to soft photon theorems with massive scalars in de Sitter spacetime were computed in [JHEP10(2023)055]. However, the massless limit of the scalar modes is ill-defined in their work. It therefore is ambiguous to take the massless limit of the soft factors. In this paper, we derive the massless scalar modes in $d$-dimensional de Sitter spacetime and use it to compute the perturbative corrections to the leading and sub-leading soft photon theorems. Our framework corresponds to tree level scattering of massless scalars followed by an emission of a soft photon in a compact region of the static patch of de Sitter. We show that our results are consistent with [JHEP10(2023)055] in the massless limit and we comment on the universality of our results.