Motion of Inertial Observers Through Negative Energy

TL;DR

This paper investigates how inertial observers moving through negative energy regions, such as near black holes or in Casimir vacuum, experience violations of quantum inequalities, challenging previous assumptions about constraints on negative energy fluxes.

Contribution

It demonstrates that certain inertial motions near black holes and in Casimir setups can produce unbounded negative energy fluxes, questioning the universality of quantum inequality constraints.

Findings

Observers orbiting near black holes see constant negative energy flux.

Slowly moving inertial observers in Casimir vacuum can violate inequalities arbitrarily.

Quantum inequalities may not constrain all negative energy fluxes.

Abstract

Recent research has indicated that negative energy fluxes due to quantum coherence effects obey uncertainty principle-type inequalities of the form $|\Delta E|\,{\Delta \tau} \lprox 1\,$. Here $|\Delta E|$ is the magnitude of the negative energy which is transmitted on a timescale $\Delta \tau$. Our main focus in this paper is on negative energy fluxes which are produced by the motion of observers through static negative energy regions. We find that although a quantum inequality appears to be satisfied for radially moving geodesic observers in two and four-dimensional black hole spacetimes, an observer orbiting close to a black hole will see a constant negative energy flux. In addition, we show that inertial observers moving slowly through the Casimir vacuum can achieve arbitrarily large violations of the inequality. It seems likely that, in general, these types of negative energy fluxes are not constrained by inequalities on the magnitude and duration of the flux. We construct a model of a non-gravitational stress-energy detector, which is rapidly switched on and off, and discuss the strengths and weaknesses of such a detector.