  We study the Bose-Einstein condensation (BEC) for a relativistic ideal gas of
bosons. In the framework of canonical thermal field theory, we analyze the role
of particles and anti-particles in the determination of BEC transition
temperature. At the BEC transition point we obtain two universal curves, i.e.
valid for any mass value: the scaled critical temperature as a function of the
scaled charge density of the Bose system, and the density ratio of
anti-particles versus the scaled critical temperature. Moreover, we numerically
investigate charge densities and condensed fraction ranging from the
non-relativistic to the ultra-relativistic temperature, where analytical
results are obtained.
