Resumo
The paper aims to provide an explanation for the tiny value of the cosmological
constant and the low vacuum energy density to represent the dark energy. To
accomplish this, we will search for a fundamental principle of symmetry in spacetime
by means of the elimination of the classical idea of rest, by including an invariant
minimum limit of speed in the subatomic world. Such a minimum speed, unattainable
by particles, represents a preferred reference frame associated with a background field
that breaks down the Lorentz symmetry. The metric of the flat space-time shall include
the presence of a uniform vacuum energy density, which leads to a negative pressure at
cosmological length scales. Thus, the equation of state for the cosmological constant
[p(pressure)= − (energy density)] naturally emerges from such a space-time with
an energy barrier of a minimum speed. The tiny values of the cosmological constant
and the vacuum energy density will be successfully obtained, being in agreement with
the observational results of Perlmutter, Schmidt and Riess