Constraining cosmologies with fundamental constants I. Quintessence and K-Essence

TL;DR

This paper investigates how measurements of fundamental constants like mu constrain cosmological models involving scalar fields, revealing that invariance in mu challenges many such theories and highlights the importance of coupling strengths.

Contribution

It provides new constraints on scalar field cosmologies by linking fundamental constant invariance to model parameters, especially the coupling constant and the equation of state.

Findings

Variation limits of mu constrain the product of w+1 and zeta_mu^2.

Weak coupling or near-zero w+1 are required for consistency with mu invariance.

Tensions arise between mu invariance and observed alpha variations.

Abstract

Many cosmological models invoke rolling scalar fields to account for the observed acceleration of the expansion of the universe. These theories generally include a potential V(phi) which is a function of the scalar field phi. Although V(phi) can be represented by a very diverse set of functions, recent work has shown the under some conditions, such as the slow roll conditions, the equation of state parameter w is either independent of the form of V(phi) or is part of family of solutions with only a few parameters. In realistic models of this type the scalar field couples to other sectors of the model leading to possibly observable changes in the fundamental constants such as the fine structure constant alpha and the proton to electron mass ratio mu. This paper explores the limits this puts on the validity of various cosmologies that invoke rolling scalar fields. We find that the limit on the variation of mu puts significant constraints on the product of a cosmological parameter w+1 times a new physics parameter zeta_mu^2, the coupling constant between mu and the rolling scalar field. Even when the cosmologies are restricted to very slow roll conditions either the value of zeta_mu must be at the lower end of or less than its expected values or the value of w+1 must be restricted to values vanishingly close to 0. This implies that either the rolling scalar field is very weakly coupled with the electromagnetic field, small zeta_mu, very weakly coupled with gravity, w+1 ~ 0 or both. These results stress that adherence to the measured invariance in mu is a very significant test of the validity of any proposed cosmology and any new physics it requires. The limits on the variation of mu also produces a significant tension with the reported changes in the value of alpha.