The Unruh effect, the equivalence principle and quantum field theory

The idea that the Unruh effect has a role in the apparent thermalization of systems produced in hadronic collisions has gained quite a lot of popularity in the last few years [1]. The systematic exploration of this idea, however, is hindered by the fact that the conceptual basis for the Unruh effect is still a controversial subject. In particular, calculations such as [2] suggest that the Unruh effect can be understood as a quantum field theory equivalent of a ”Coriolis force” accounting for the non-inertiality of the reference frame rather than an ”objective” physical effect.The correctness of this picture does not rule out the Unruh thermalization scenario, but suggests that it can be understood as a version of strong-field thermalization viewed in a non-inertial frame. We use neutrino oscillations as a laboratory to this example, show that it indicates a fundamental issue between the equivalence principle and quantum field theory and suggest ways to resolve this.