Lectures on quantum energy inequalities

TL;DR

This paper introduces Quantum Energy Inequalities (QEIs), explaining their derivation using advanced quantum field theory techniques, and discusses their implications in curved spacetime and specific quantum field models.

Contribution

It provides a comprehensive introduction to QEIs, details their derivation using microlocal analysis and algebraic QFT, and computes specific examples for scalar and conformal fields.

Findings

QEIs hold for free scalar fields in curved spacetime

Derived QEIs for 2D conformal field theories

Determined probability distributions for stress-energy measurements

Abstract

Quantum field theory violates all the classical energy conditions of general relativity. Nonetheless, it turns out that quantum field theories satisfy remnants of the classical energy conditions, known as Quantum Energy Inequalities (QEIs), that have been developed by various authors since the original pioneering work of Ford in 1978. These notes provide an introduction to QEIs and also to some of the techniques of quantum field theory in curved spacetime (particularly, the use of microlocal analysis together with the algebraic formulation of QFT) that enable rigorous and general QEIs to be derived. Specific examples are computed for the free scalar field and their consequences are discussed. QEIs are also derived for the class of unitary, positive energy conformal field theories in two spacetime dimensions. In that setting it is also possible to determine the probability distribution for individual measurements of certain smearings of the stress-energy tensor in the vacuum state.