# Non-thermal signature of the Unruh effect in field mixing

## TL;DR

This paper investigates how field mixing affects the Unruh effect for an accelerated observer, revealing a non-thermal signature in the radiation spectrum due to the interplay of quantum field transformations.

## Contribution

It introduces a novel analysis of field mixing in accelerated frames, showing the Unruh radiation's spectrum deviates from thermal behavior in this context.

## Key findings

- Unruh radiation loses its thermal interpretation due to field mixing.
- The modified spectrum is explicitly calculated for small mass differences.
- Field mixing alters the expected thermal signature of the Unruh effect.

## Abstract

Mixing transformations for a uniformly accelerated observer (Rindler observer) are analyzed within the quantum field theory framework as a basis for investigating gravitational effects on flavor oscillations. In particular, the case of two charged boson fields with different masses is discussed. In spite of such a minimal setting, the standard Unruh radiation is found to loose its characteristic thermal interpretation due to the interplay between the Bogolubov transformation hiding in field mixing and the one arising from the Rindler spacetime structure. The modified spectrum detected by the Rindler observer is explicitly calculated in the limit of small mass difference.