Holographic dark energy and cosmic coincidence

TL;DR

This paper shows that interacting holographic dark energy with pressureless dark matter can naturally explain the cosmic coincidence problem and accommodate the universe's transition from deceleration to acceleration.

Contribution

It demonstrates that a specific interaction setup leads to a constant energy density ratio, addressing the coincidence problem, and explores variable saturation effects on cosmic evolution.

Findings

Interaction implies a constant energy density ratio, solving the coincidence problem.

Equation of state depends on interaction strength.

Transition from decelerated to accelerated expansion is compatible with variable saturation.

Abstract

In this Letter we demonstrate that any interaction of pressureless dark matter with holographic dark energy, whose infrared cutoff is set by the Hubble scale, implies a constant ratio of the energy densities of both components thus solving the coincidence problem. The equation of state parameter is obtained as a function of the interaction strength. For a variable degree of saturation of the holographic bound the energy density ratio becomes time dependent which is compatible with a transition from decelerated to accelerated expansion.