Journal of High Energy Physics (Mar 2023)

A note on the asymptotic symmetries of electromagnetism

  • Oscar Fuentealba,
  • Marc Henneaux,
  • Cédric Troessaert

DOI
https://doi.org/10.1007/JHEP03(2023)073
Journal volume & issue
Vol. 2023, no. 3
pp. 1 – 25

Abstract

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Abstract We extend the asymptotic symmetries of electromagnetism in order to consistently include angle-dependent u(1) gauge transformations ϵ that involve terms growing at spatial infinity linearly and logarithmically in r, ϵ ~ a(θ, φ)r + b(θ, φ) ln r + c(θ, φ). The charges of the logarithmic u(1) transformations are found to be conjugate to those of the O $$ \mathcal{O} $$ (1) transformations (abelian algebra with invertible central term) while those of the O $$ \mathcal{O} $$ (r) transformations are conjugate to those of the subleading O $$ \mathcal{O} $$ (r −1) transformations. Because of this structure, one can decouple the angle-dependent u(1) asymptotic symmetry from the Poincaré algebra, just as in the case of gravity: the generators of these internal transformations are Lorentz scalars in the redefined algebra. This implies in particular that one can give a definition of the angular momentum which is free from u(1) gauge ambiguities. The change of generators that brings the asymptotic symmetry algebra to a direct sum form involves non linear redefinitions of the charges. Our analysis is Hamiltonian throughout and carried at spatial infinity.

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