Beta Function Quintessence Cosmological Parameters and Fundamental Constants I: Power and Inverse Power Law Dark Energy Potentials

TL;DR

This paper introduces a beta function formalism to analytically solve for cosmological parameters in scalar field dark energy models, demonstrating its accuracy and revealing that the Hubble parameter is largely insensitive to potential power.

Contribution

It presents a novel beta function approach for analytic solutions in scalar field cosmologies, applicable to power law and inverse power law dark energy potentials.

Findings

Hubble parameter is nearly insensitive to potential power.

Lambda CDM corresponds to zero power law potential.

Beta function provides accurate approximations of cosmological parameters.

Abstract

This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar $\phi$ with respect to the natural log of the scale factor $a$, $\beta(\phi)=\frac{d \phi}{d \ln(a)}$. Once the beta function is specified, modulo a boundary condition, the evolution of the scalar $\phi$ as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated "beta potential" is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are that are not calculable using only the model action. As an example this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that $\Lambda$CDM is part of the family of quintessence cosmology power law potentials with a power of zero.