Asymptotic Dynamics in Perturbative Quantum Gravity and BMS Supertranslations

TL;DR

This paper explores how Faddeev-Kulish states in perturbative quantum gravity encode BMS supertranslation charges, ensuring conservation laws and resolving infrared divergences by characterizing superselection sectors.

Contribution

It demonstrates that FK asymptotic states carry BMS supertranslation charges, linking vacuum transitions to superselection sectors and addressing infrared issues in quantum gravity.

Findings

FK states carry BMS supertranslation charges

Conservation of charges prevents superselection sector transitions

FK graviton clouds implement vacuum transitions in scattering

Abstract

Recently it has been shown that infrared divergences in the conventional S-matrix elements of gauge and gravitational theories arise from a violation of the conservation laws associated with large gauge symmetries. These infrared divergences can be cured by using the Faddeev-Kulish (FK) asymptotic states as the basis for S-matrix elements. Motivated by this connection, we study the action of BMS supertranslations on the FK asymptotic states of perturbative quantum gravity. We compute the BMS charge of the FK states and show that it characterizes the superselection sector to which the state belongs. Conservation of the BMS charge then implies that there is no transition between different superselection sectors, hence showing that the FK graviton clouds implement the necessary vacuum transition induced by the scattering process.