  If Lorentz invariance is only an approximate property of equations describing
a sector of matter above some critical distance scale, the speed of light c
will not necessarily be the only critical speed in vacuum. Superluminal sectors
of matter may exist related to new degrees of freedom not yet discovered
experimentally. The new particles would not be tachyons: they may feel
different minkowskian space-times with critical speeds much higher than c and
behave kinematically like ordinary particles apart from the difference in
critical speed. We present a discussion of possible physical (theoretical and
experimental) and cosmological implications of such a scenario, assuming that
the superluminal sectors couple weakly to ordinary matter.

High Energy Physics - Phenomenology;Astrophysics;General Relativity and Quantum Cosmology;High Energy Physics - Theory;General Physics