  We study quantum gravity signatures emerging from phenomenologically
motivated multiscale models, spectral actions, and Causal Set Theory within the
detector approach to the Unruh effect. We show that while the Unruh temperature
is unaffected, Lorentz-invariant corrections to the two-point function leave a
characteristic fingerprint in the induced emission rate of the accelerated
detector. Generically, quantum gravity models exhibiting dynamical dimensional
reduction exhibit a suppression of the Unruh rate at high energy while the rate
is enhanced in Kaluza-Klein theories with compact extra dimensions. We quantify
this behavior by introducing the "Unruh dimension" as the effective spacetime
dimension seen by the Unruh effect and show that it is related, though not
identical, to the spectral dimension used to characterize spacetime in quantum
gravity. We comment on the physical origins of these effects and their
relevance for black hole evaporation.
