Decay of uniformly rotating particles

TL;DR

The paper investigates whether the circular Unruh effect requires a thermal bath for uniformly rotating observers. Using general covariance, they analyze decay processes of a non-inertial two-level system interacting with scalar fields and show that inertial and comoving decay rates can be identical without invoking a bath, thanks to negative-energy quanta allowed by the absence of a global vacuum. An analytic treatment of a simplified decay process yields an invariant decay rate that matches a detector's response and displays a seesaw dependence on the energy gap $\Delta E$. This work clarifies that the circular Unruh effect is effectively non-thermal and tied to the lack of a global vacuum, with implications for the stability of rotating particles and potential analogue-gravity experiments.

Abstract

In this paper, we revisit the interpretation of the circular Unruh effect. To this aim, we rely on the principle of general covariance applied to the decay properties of non-inertial particles. Specifically, we show how the tree-level decay rate of an inverse-$β$ process involving scalar fields does not require the introduction of a thermal (or non-thermal) bath in the comoving frame to be a scalar under general coordinate transformations. Instead, we interpret any decay process as an emission of negative-energy quanta, whose existence is motivated by the absence of a global vacuum state for uniformly rotating observers. This implies that, in principle, no uniformly rotating particle can be regarded as stable.