  We study the way Lorentz covariance can be reconstructed from Matrix Theory
as a IMF description of M-theory. The problem is actually related to the
interplay between a non abelian Dirac-Born-Infeld action and Super-Yang-Mills
as its generalized non-relativistic approximation. All this physics shows up by
means of an analysis of the asymptotic expansion of the Bessel functions
$K_\nu$ that profusely appear in the computations of amplitudes at finite
temperature and solitonic calculations. We hope this might help to better
understand the issue of getting a Lorentz covariant formulation in relation
with the $N\to +\infty$ limit. There are also some computations that could be
of some interest in Relativistic Statistical Mechanics.
