We reconsider Lorentz Violation (LV) at the fundamental level. We show that
Lorentz Violation is intimately connected with gravity and that LV couplings in
QFT must always be fields in a gravitational sector. Diffeomorphism invariance
must be intact and the LV couplings transform as tensors under coordinate/frame
changes. Therefore searching for LV is one of the most sensitive ways of
looking for new physics, either new interactions or modifications of known
ones. Energy dissipation/Cerenkov radiation is shown to be a generic feature of
LV in QFT. A general computation is done in strongly coupled theories with
gravity duals. It is shown that in scale invariant regimes, the energy
dissipation rate depends non-triviallly on two characteristic exponents, the
Lifshitz exponent and the hyperscaling violation exponent.Comment: LateX, 51 pages, 9 figures. (v2) References and comments added.
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