Note on asymptotic symmetry of massless scalar field at null infinity

TL;DR

This paper investigates the asymptotic symmetry properties of massless scalar fields at null infinity, generalizing existing notions to gauge-free theories and confirming results through Hamiltonian and covariant phase space analyses.

Contribution

It introduces a generalized concept of asymptotic symmetry for massless scalar fields without gauge symmetry and verifies the results using two different analytical methods.

Findings

Results align with previous findings for dual 2-form fields

Confirms consistency with scalar soft theorem

Provides a new perspective on asymptotic symmetries in scalar theories

Abstract

In this article we address the question of asymptotic symmetry of massless scalar field at null infinity. We slightly generalize notion of asymptotic symmetry in order to make sense for the theory without gauge symmetry. Derivations of the results are done in two different ways, using Hamiltonian analysis and using covariant phase space. The results are in agreement with the ones previously obtained by various authors for dual 2-form field and with the results obtained starting from scalar soft theorem.