Poincar\'e invariance and the Unruh effect

TL;DR

This paper argues that when quantum field theory is formulated with explicit causality, the vacuum appears empty and the Unruh effect disappears, challenging the conventional understanding of acceleration-induced thermal radiation.

Contribution

It demonstrates that enforcing causality in quantum field theory eliminates the virtual particles responsible for the Unruh effect, suggesting the effect is an artifact of non-causal formulations.

Findings

Vacuum is empty when causality is enforced in quantum field theory.

Acceleration does not produce a thermal gas in a causal vacuum.

Standard Unruh effect calculations omit a cancelling contribution.

Abstract

In quantum field theory, the vacuum is popularly considered to be a complex medium populated with virtual particle + antiparticle pairs. To an observer experiencing uniform acceleration, it is generally held that these virtual particles become real, appearing as a gas at a temperature that grows with the acceleration. This is the Unruh effect. However, it has been shown that vacuum complexity is an artifact, produced by treating quantum field theory in a manner that does not manifestly enforce causality. Choosing a quantization approach that patently enforces causality, the quantum field theory vacuum is barren, bereft even of virtual particles. We show that acceleration has no effect on a trivial vacuum; hence, there is no Unruh effect in such a treatment of quantum field theory. Since the standard calculations suggesting an Unruh effect are formally consistent, insofar as they have been completed, there must be a cancelling contribution that is omitted in the usual analyses. We argue that it is the dynamical action of conventional Lorentz transformations on the structure of an Unruh detector.