Reconstructing inflation and reheating in the framework of a generalized $\mathcal{F}(H)$ Friedmann equation

TL;DR

This paper develops a new method to reconstruct inflationary models within a generalized Friedmann framework, connecting the Hubble parameter, potential, and spectral index, and constrains models using current observational data.

Contribution

It introduces a novel reconstruction methodology for inflation and reheating in modified Friedmann equations characterized by an arbitrary function of the Hubble parameter.

Findings

Reconstructed the Hubble parameter and potential for specific $\\mathcal{F}(H)$ models.

Constrained inflationary parameters using Planck and BICEP/Keck data.

Analyzed reheating temperature and e-folds with a constant equation of state.

Abstract

The reconstruction of an inflationary universe considering the parametrization of the scalar spectral index as a function of the number of $e-$folds in the framework of a modified Friedmann equation is analyzed. In this context, we examine the possibility of reconstructing the Hubble parameter together with the effective potential considering a modified Friedmann equation specified by $\mathcal{F}(H)\propto \rho$, where $\mathcal{F}(H)$ corresponds to an arbitrary function of the Hubble parameter $H$ and $\rho$ denotes the energy density associated with the matter in the universe. To reconstruct the background variables during the inflationary scenario, we develop a new methodology by expressing the spectral index in terms of the Hubble parameter and its derivatives. Thus, we obtain a general formalism for the reconstruction of the inflation, using the slow roll approximation together with the parametrization of the scalar spectral index as a function of the number of $e-$folds $N$. As specific examples, we consider the simplest attractor $n_s-1=-2/N$ together with different functions $\mathcal{F}(H)$, associated to the modified Friedmann equation, to rebuild the Hubble parameter and the effective potential in terms of the scalar field $\phi$. Additionally, we examine the reheating epoch by considering a constant equation of state parameter, in which we determine the temperature and the number of e-folds during this epoch, using the background variables found during the reconstruction of the different $\mathcal{F}(H)-$models studied. Besides, we constrain the different parameters associated with the reconstructed inflationary $\mathcal{F}(H)-$models during the epochs of inflation and reheating, using current astronomical data from Planck and BICEP/Keck results.