Speaker
Description
Energy plays a ubiquitous role in physics. In GR, energy conditions forbid exotic spacetimes such as traversable wormholes, and play a central role in singularity theorems and black hole thermodynamics. Yet all quantum field theories violate all pointwise energy conditions: states with arbitrarily negative local energy density always exist. In this talk, I will discuss what survives of energy inequalities once matter is quantised. I will start by reviewing the classical energy conditions and their role in gravity. I will then introduce several quantum energy inequalities—including the averaged null energy condition, the quantum null energy condition, and smeared null energy bounds—which place nontrivial constraints on negative energy despite the failure of classical energy conditions. Finally, I will discuss how these quantum energy inequalities can be used to recover gravitational results that were previously derived from classical pointwise energy conditions, focusing on modern quantum singularity theorems. Along the way, I will describe recent progress on higher-dimensional bounds on smeared null energy and their connections to causality, entropy, and quantum information.