We will look for an implementation of new symmetries in the space-time structure and their cosmological implications. This search will allow us to find a unified vision for electrodynamics and gravitation. We will attempt to develop a heuristic model of the electromagnetic nature of the electron, so that the influence of the gravitational field on the electrodynamics at very large distances leads to a reformulation of our comprehension of the space- time structure at quantum level through the elimination of the classical idea of rest. This will lead us to a modification of the relativistic theory by introducing the idea about a universal minimum limit of speed in the space- time. Such a limit, unattainable by the particles, represents a preferred frame associated with a universal background field (a vacuum energy), enabling a fundamental understanding of the quantum uncertainties. The structure of space-time becomes extended due to such a vacuum energy density, which leads to a negative pressure at the cosmological scales as an anti-gravity, playing the role of the cosmological constant. The tiny values of the vacuum energy density and the cosmological constant will be successfully obtained, being in agreement with current observational results.