Resolving Puzzles of Massive Gravity with and without violation of Lorentz symmetry

Understand

We perform a systematic study of various versions of massive gravity with and without violation of Lorentz symmetry in arbitrary dimension.

• These theories are well known to possess very unusual properties, unfamiliar from studies of gauge and Lorentz invariant models.
• These peculiarities are caused by mixing of familiar transverse fields with revived longitudinal and pure gauge (Stueckelberg) fields and are all seen already in quadratic approximation.
• They are all associated with non-trivial dispersion laws, which easily allow superluminal propagation, ghosts, tachyons and essential irrationalities.