Spacetime in Semiclassical Gravity

TL;DR

This paper reviews the semiclassical theory of gravity, focusing on quantum effects in black holes and cosmology, energy condition violations, and initial steps toward understanding spacetime fluctuations beyond semiclassical approximation.

Contribution

It provides a summary of key aspects of semiclassical gravity, highlighting recent developments and open questions in quantum effects and spacetime fluctuations.

Findings

Quantum effects influence black hole physics and cosmology.

Quantum violations of energy conditions occur and are constrained by inequalities.

Initial understanding of spacetime geometry fluctuations beyond semiclassical gravity.

Abstract

This article will summarize selected aspects of the semiclassical theory of gravity, which involves a classical gravitational field coupled to quantum matter fields. Among the issues which will be discussed are the role of quantum effects in black hole physics and in cosmology, the effects of quantum violations of the classical energy conditions, and inequalities which constrain the extent of such violations. We will also examine the first steps beyond semiclassical gravity, when the effects of spacetime geometry fluctuations start to appear.