Unifying energy-entropy bounds in semiclassical gravity

Abstract

We revisit bounds on energy and entropy in semiclassical gravity, aiming to strengthen and unify established bounds, in particular the quantum focussing conjecture (QFC) and the smeared null energy condition (SNEC). Both the QFC and SNEC have important applications and are the strongest in their respective hierarchies; however, neither implies the other, nor reduces to the null energy condition (NEC) in the classical limit. To that end, we define a new class of bounds dubbed gravitational energy-entropy conditions (GEECs) that imply both the QFC and SNEC, and reduce to the NEC classically. We construct an explicit family of GEECs by imposing the defining criteria on a broad set of stress tensor bounds, and constrain its remaining parameter space through test cases, in an effective field theory-inspired approach. Our GEECs are powerful candidate bounds on energy and entropy in semiclassical gravity.