Gravitational memory effects in Brans-Dicke theory

TL;DR

This paper explores gravitational memory effects in Brans-Dicke theory, linking them to asymptotic symmetries and fluxes at null infinity, revealing new insights into vacuum transitions and memory phenomena.

Contribution

It uncovers the origin of displacement memory effects in Brans-Dicke theory and their relation to asymptotic symmetries and fluxes, extending understanding beyond general relativity.

Findings

Displacement memory in tensor sector arises from null energy fluxes.

Scalar sector vacuum transition is driven by angular momentum fluxes.

Memory effects are constrained by flux-balance laws.

Abstract

There exist gravitational memory effects in Brans-Dicke theory. They are closely related to the Bondi-Metzner-Sachs symmetries living on the null infinity in an isolated system. By studying the asymptotically flat spacetime in Brans-Dicke theory and the asymptotic symmetries, one discovers that the displacement memory effect in the tensor sector is due to the vacuum transition caused by the null energy fluxes panetrating the null infinity, while in the scalar sector, the vacuum transition is due to the angular momentum fluxes. Together with the spin and the center-of-mass memory effects, the displacement memories are constrained by various flux-balance laws.