Constraining Barrow entropy-based Cosmology with power-law inflation

TL;DR

This paper explores how a modified cosmological model based on Barrow entropy influences inflationary dynamics, constraining quantum gravitational effects using observational data from Planck.

Contribution

It introduces a Barrow entropy-based framework into inflationary cosmology and derives constraints on quantum gravitational effects from observational data.

Findings

Barrow entropy affects inflationary dynamics, allowing slow-roll but not kinetic inflation.

The Barrow exponent is constrained to be less than approximately 10^{-4} by Planck data.

Modified Friedmann equations are derived from thermodynamics with Barrow entropy.

Abstract

We study the inflationary era of the Universe in a modified cosmological scenario based on the gravity-thermodynamics conjecture with Barrow entropy instead of the usual Bekenstein-Hawking one. The former arises from the effort to account for quantum gravitational effects on the horizon surface of black holes and, in a broader sense, of the Universe. First, we extract modified Friedmann equations from the first law of thermodynamics applied to the apparent horizon of a Friedmann- Robertson-Walker Universe in (n + 1)-dimensions. Assuming a power-law behavior for the scalar inflaton field, we then investigate how the inflationary dynamics is affected in Barrow cosmological setup. We find that the inflationary era may phenomenologically consist of the slow-roll phase, while Barrow entropy is incompatible with kinetic inflation. By demanding observationally consistency of the scalar spectral index and tensor-to-scalar ratio with recent Planck data, we finally constrain Barrow exponent to $\Delta\lesssim10^{-4}$.