Luis Gonzalez-Mestres
Lorentz invariance and superluminal particles
(35K, LaTex)
ABSTRACT. If textbook Lorentz invariance is actually
a property of the equations describing a sector
of matter above some critical distance scale,
several sectors of matter with different
critical speeds in vacuum can coexist and an absolute rest frame (the vacuum
rest frame, possibly related to the local rest frame of the expanding Universe)
may exist without contradicting the apparent Lorentz invariance felt by
"ordinary" particles (particles with critical speed in vacuum equal to $c$ ,
the speed of light). Sectorial Lorentz invariance, reflected by the fact that
all particles of a given dynamical sector have the same critical speed in
vacuum, will then be an expression of a fundamental sectorial symmetry
(e.g. preonic grand unification or extended supersymmetry) protecting a
parameter of the equations of motion.
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We study the breaking of Lorentz invariance in such a scenario, with
emphasis on mixing between the "ordinary"
sector and a superluminal sector, and discuss with examples the consequences
of existing data. The sectorial universality of the
value of the high-energy speed in vacuum, even exact, does not necessarily
imply that Lorentz invariance is not violated and does not by itself exclude
the possibility to produce superluminal particles at accelerators or to find
them in experiments devoted to high-energy cosmic rays. Similarly, the
stringent experimental bounds on Lorentz symmetry violation at low energy
cannot be extrapolated to high-energy phenomena.
Several basic questions
related to possible effects of Lorentz symmetry violation are discussed,
and potential signatures are examined.