Modified cosmology through spacetime thermodynamics and Barrow horizon entropy

TL;DR

This paper explores modified cosmological models derived from spacetime thermodynamics using Barrow entropy, revealing new effective dark energy behavior and potential for crossing the phantom divide, with the universe approaching de Sitter space asymptotically.

Contribution

It introduces a novel cosmological framework based on Barrow entropy, extending gravity-thermodynamics correspondence and analyzing its impact on universe evolution.

Findings

Effective dark energy density evolution is derived analytically.

The dark-energy equation-of-state can be quintessence, phantom, or crossing the divide.

The universe asymptotically approaches a de Sitter phase.

Abstract

We present modified cosmological scenarios that arise from the application of the "gravity-thermodynamics" conjecture, using the Barrow entropy instead of the usual Bekenstein-Hawking one. The former is a modification of the black hole entropy due to quantum-gravitational effects that deform the black-hole horizon by giving it an intricate, fractal structure. We extract modified cosmological equations which contain new extra terms that constitute an effective dark-energy sector, and which coincide with the usual Friedmann equations in the case where the new Barrow exponent acquires its Bekenstein-Hawking value. We present analytical expressions for the evolution of the effective dark energy density parameter, and we show that the universe undergoes through the usual matter and dark-energy epochs. Additionally, the dark-energy equation-of-state parameter is affected by the value of the Barrow deformation exponent and it can lie in the quintessence or phantom regime, or experience the phantom-divide crossing. Finally, at asymptotically large times the universe always results in the de-Sitter solution.