Cosmological dynamics of mimetic gravity

TL;DR

This paper investigates the dynamical behavior of mimetic gravity with various potentials, demonstrating its ability to model the universe's thermal history, late-time acceleration, and potentially unify dark matter and dark energy.

Contribution

It provides a comprehensive phase-space analysis of mimetic gravity with general potentials, revealing its capacity to describe cosmic evolution and address the coincidence problem.

Findings

Successfully models radiation, matter, and dark-energy eras

Can approach de Sitter or scaling attractors at late times

Unifies dark matter and dark energy with inverse square potential

Abstract

We present a detailed investigation of the dynamical behavior of mimetic gravity with a general potential for the mimetic scalar field. Performing a phase-space and stability analysis, we show that the scenario at hand can successfully describe the thermal history of the universe, namely the successive sequence of radiation, matter, and dark-energy eras. Additionally, at late times the universe can either approach a de Sitter solution, or a scaling accelerated attractor where the dark-matter and dark-energy density parameters are of the same order, thus offering an alleviation of the cosmic coincidence problem. Applying our general analysis to various specific potential choices, including the power-law and the exponential ones, we show that mimetic gravity can be brought into good agreement with the observed behavior of the universe. Moreover, with an inverse square potential we find that mimetic gravity offers an appealing unified cosmological scenario where both dark energy and dark matter are characterized by a single scalar field, and where the cosmic coincidence problem is alleviated.