Luis Gonzalez-Mestres
Physical and cosmological implications of a possible class of particles
able to travel faster than light
(46K, LaTex)
ABSTRACT. The apparent Lorentz invariance of the laws of physics does not imply that
space-time is indeed minkowskian. Matter made of solutions of Lorentz-invariant
equations would feel a relativistic space-time even if the actual space-time
had a quite different geometry (f.i. a galilean space-time).
A typical example is provided by sine-Gordon solitons in a galilean world.
A "sub-world" restricted to such solitons would be "relativistic", with the
critical speed of solitons playing the role of the speed of light.
Only the study of the deep structure of matter will unravel the actual geometry
of space and time, which we expect to be scale-dependent and determined by the
properties of matter itself.
If Lorentz invariance is only an approximate property of equations describing
a sector of matter at a given scale, an absolute frame (the "vacuum rest
frame") may exist without contradicting the minkowskian structure of the
space-time felt by ordinary particles. But c , the speed of light, will not
necessarily be the only critical speed in vacuum: for instance, superluminal
sectors of matter may exist related to new degrees of freedom
not yet discovered experimentally. Such 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. Because of the very high critical speed in
vacuum, superluminal particles will have very large rest energies.
At speed v > c , they are expected to release "Cherenkov" radiation (ordinary
particles) in vacuum.
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. The production of
superluminal particles may yield clean signatures in experiments at very
high energy accelerators. The breaking of Lorentz invariance will be basically
a very high energy and very short distance phenomenon, not incompatible with
the success of standard tests of relativity. Gravitation will undergo
important modifications when extended to the superluminal sectors. The Big
Bang scenario, as well as large scale structure, can be strongly influenced
by the new particles. If superluminal
particles exist, they could provide most of the cosmic (dark) matter and
produce very high energy cosmic rays compatible with unexplained discoveries
reported in the literature.