Gravitational quantum friction and the information-loss problem

Abstract

We study the gravitational collapse of a shell, modeled as a coherent state of quantum matter. Without adding any physics beyond semiclassical gravity, we show that the universal gravitational coupling between matter and geometry induces an interaction between the shell and the negative-frequency modes present in the $|in \rangle$ vacuum state. We find that this interaction occurs unavoidably immediately after a trapping horizon forms, making it a universal feature of semiclassical gravitational collapse. The resulting transfer of energy from the collapsing matter to outgoing Hawking radiation acts as a \textit{gravitational quantum friction}, opposing the formation of trapped regions while simultaneously imprinting the information carried by the collapsing matter onto the emitted quanta. We discuss the implications of this mechanism for the black hole information-loss problem and speculate about the possible endpoints of collapse, potentially preventing horizon and singularity formation.