Unruh Effect for Mixed Neutrinos and the KMS Condition

The quantization of mixed (neutrino) fields in an accelerated background reveals a non-thermal nature for Unruh radiation, which can be fitted by a Tsallis-like distribution function. However, for relativistic flavor neutrinos, which are represented by the standard Pontecorvo states, such a correction turns out to be negligible and thermality is restored. We show that the usage of Pontecorvo states for the calculation of the decay rate of an accelerated proton in the laboratory and comoving frames leads to consistent results and correctly implements the KMS thermal condition. Thus, the employment of these states in the above framework is not at odds with the principle of general covariance, in contrast to recent claims in the literature.