General relativistic, nonstandard model for the dark sector of the Universe

TL;DR

This paper develops a general relativistic self-gravitating fluid model for the Universe's dark sector, explaining cosmic acceleration without negative pressure and linking it to a sign-changing curvature, extending previous nonrelativistic models.

Contribution

It introduces a parameter-free relativistic model of the dark sector that reinterprets cosmic acceleration through a dynamic energy density sign change.

Findings

Cosmic acceleration arises from a sign change in energy density, not negative pressure.

The model's equations match nonrelativistic counterparts but offer a new physical interpretation.

Derived a gravitational potential equation for galactic halos within this framework.

Abstract

We present a general relativistic version of the self-gravitating fluid model for the dark sector of the Universe (darkon fluid) introduced in Phys. Rev. 80 (2009) 083513 and extended and reviewed in Entropy (2013) 559. This model contains no free parameters in its Lagrangian. The resulting energy-momentum tensor is dustlike with a nontrivial energy-flow. In an approximation valid at sub-Hubble scales we find that the cosmic acceleration is not attributed to any kind of negative pressure but it is due to a dynamically determined sign change of the energy density. This property turns out to be equivalent to a time-dependent, sign changing curvature. The cosmological equations obtained agree with those of the nonrelativistic model but they are given a new physical interpretation. Furthermore we have derived the self-consistent equation to be satisfied by the nonrelativistic gravitational potential produced by a galactic halo in our model from a weak field limit of a generalized Tolman-Oppenheimer-Volkoff equation.