f(R) Gravity in an Ellipsoidal Universe

TL;DR

This paper introduces a new anisotropic $f(R)$ gravity-based cosmological model, called $oldsymbol{\gammaoldsymbol{\delta}CDM}$, which modifies the relation between energy densities and the Hubble parameter, offering an alternative to $oldsymbol{\Lambda CDM}$ with observational support.

Contribution

The paper develops a novel anisotropic $f(R)$ gravity model with weighted energy contributions, differing from standard cosmology, and tests its observational viability.

Findings

Model fits observational data well.

Supports the idea of cosmological black hole coupling.

Provides an alternative to $oxed{ ext{Lambda CDM}}$ without a cosmological constant.

Abstract

We propose a new model of cosmology based on an anisotropic background and a specific $f(R)$ theory of gravity. It is shown that field equations of $f(R)$ gravity in a Bianchi type I background give rise to a modified Friedmann equation. This model contains two important parameters: $\gamma$ and $\delta$. We, thus, simply call our model $\gamma\delta$CDM. It is distinguished in two important aspects from the $\Lambda$CDM model: firstly, the contribution of different energy densities to the Hubble parameter are weighted with different weights, and then, dependence of energy densities to redshift is modified as well. This unorthodox relation of energy content to Hubble parameter brings forth a new way of interpreting the cosmological history. This solution does not allow the existence of a cosmological constant component, however, a dark energy contribution with dependence on redshift is possible. We tested observational relevance of the new solution by best fitting to different data sets. We found that our model could accommodate the idea of cosmological coupling of black holes.