Polytropic DM fluid: An Occam’s razor approach to the DE concept

Abstract

In the last 25 years, a continuously growing list of observational data has verified the existence of a distributed energy component in the Universe, i.e., one that does not cluster at any scale, namely, the dark energy (DE). The determination of DE’s exact nature has become one of the biggest problems in theoretical physics and cosmology; consequently, (too) many models have been proposed. Here, we review a series of theoretical results regarding a conventional approach to the DE concept. In our model, the Universe is filled with a perfect fluid of self-interacting dark matter (DM) the volume elements of which perform polytropic flows. Consequently, the energy of this fluid’s internal motions is also considered as a source of the universal gravitational field and, as we demonstrate, can compensate the DE needed to compromise spatial flatness in an accelerating Universe. In the polytropic DM model so consider, there is no disagreement between observations and the theoretical prediction of the supernovae Type Ia distribution. In fact, the cosmological model with matter content in the form of a polytropic DM fluid can interpret to high accuracy all the observational data associated with the recent history of Universe expansion, thus arising as a mighty contestant for a viable alternative to ΛCDM model.