On electromagnetic and colour memory in even dimensions

TL;DR

The work develops a comprehensive, dimension-sensitive account of memory effects from electromagnetic and Yang–Mills radiation reaching null infinity in even dimensions, linking classical (ordinary and null) memory, as well as quantum-phase and colour memory, to residual large gauge transformations in the Lorenz gauge. By performing detailed asymptotic expansions and a recursive gauge-fixing procedure, memory is shown to reside at subleading Coulombic order (scaling as $r^{4-D}$) and to be encoded in components like $A_i^{(D-4)}$, with phase and colour memories arising from parallel transport and non-Abelian evolution. The authors extend the Maxwell analysis to polyhomogeneous (logarithmic) expansions to reveal extended asymptotic symmetries and well-defined surface charges, and relate these charges to Weinberg’s soft-photon theorem via Ward identities. Collectively, the results illuminate how memory effects and asymptotic symmetries interconnect across Abelian and non-Abelian gauge theories in higher even dimensions, with potential links to quantum memory and soft theorems in arbitrary $D$.

Abstract

We explore memory effects associated to both Abelian and non-Abelian radiation getting to null infinity, in arbitrary even spacetime dimensions. Together with classical memories, linear and non-linear, amounting to permanent kicks in the velocity of the probes, we also discuss the higher-dimensional counterparts of quantum memory effects, manifesting themselves in modifications of the relative phases describing a configuration of several probes. In addition, we analyse the structure of the asymptotic symmetries of Maxwell's theory in any dimension, both even and odd, in the Lorenz gauge.