Luis Gonzalez-Mestres
High-energy nuclear physics with Lorentz symmetry violation
(55K, LaTex)
ABSTRACT. If textbook Lorentz invariance is actually
a property of the equations describing a sector of the excitations of vacuum
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) 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. Furthermore, the sectorial Lorentz
symmetry may be only a low-energy limit, in the same way as the relation
$\omega $ (frequency) = $c_s$ (speed of sound) $k$ (wave vector) holds for
low-energy phonons in a crystal. In this context, phenomena
such as the absence of Greisen-Zatsepin-Kuzmin cutoff for protons and nuclei
and the stability of unstable particles (e.g. neutron, several nuclei...)
at very high energy are basic properties of a wide
class of noncausal models where local Lorentz invariance is broken
introducing a fundamental length. Observable phenomena are expected
at very short wavelength scales, even if
Lorentz symmetry violation remains invisible to standard low-energy
tests. We present a detailed discussion of the implications of Lorentz symmetry
violation for very high-energy nuclear physics.