  Both Stefan-Boltzmann law and the Casimir effect, in a universe described by
the FRW metric with zero curvature, are calculated. These effects are described
by Thermo Field Dynamics (TFD). The gravitational energy-momentum tensor is
defined in the context of Teleparallel Equivalent to General Relativity (TEGR).
Each of the two effects gives a consistent prediction with what is observed on
a cosmological scale. One of the effect establishes a minimum range for the
deceleration parameter. While another leads to the conclusion that a possible
cosmological constant has a very small order of magnitude.
