On the Relation Between Unruh and Sokolov–ternov Effects

We show that the Sokolov–Ternov effect — the depolarization of particles in storage rings coming from synchrotron radiation due to spin flip transitions — is physically equivalent to the Unruh effect for circular acceleration if one uses a spin-1/2 particle as the Unruh–DeWitt detector. It is shown that for the electron, with gyromagnetic number g ≈ 2, the exponential contribution to the polarization, which usually characterizes the Unruh effect, is "hidden" in the standard Sokolov–Ternov effect making it hard to observe. Thus, our conclusions are different in detail from previous work.