Cosmological dynamics of gravitating hadron matter

TL;DR

This paper investigates the evolution of anisotropic cosmologies with Skyrme matter, revealing bounds on the cosmological constant and couplings necessary to avoid singularities, with implications for low-energy QCD and gravitational coupling.

Contribution

It provides the first detailed analysis of anisotropic cosmologies with Skyrme matter, establishing bounds on parameters to ensure non-singular solutions and highlighting the intrinsic nature of these bounds.

Findings

Bounds on the cosmological constant depend on initial conditions.

Skyrme coupling bounds are similar across different cosmological models.

Upper bound on the cosmological constant is vastly lower than quantum field theory estimates.

Abstract

Anisotropic cosmologies are studied in the case where the matter source is given by the Skyrme model which is an effective description of low energy QCD. The dynamical evolution of the Kantowski-Sachs and Bianchi-I universes are analyzed in depth. In both situations in order for solutions to exist and at the same time to avoid finite time future singularities, bounds on the value of the cosmological constant and on the values of the Skyrme couplings must be set. The upper bound on the cosmological constant, which depends also on the initial conditions is closely related to the fact that the baryons appear below 1 GeV. The upper bound on the cosmological constant is actually 72 orders of magnitudes lower than the standard estimations from quantum field theory. The lower bound on the cosmological constant and the bounds on the Skyrme couplings are due to the peculiar combination of nonlinear terms in the Skyrme model. It is worth to point out that bounds on the Skyrme couplings occur in similar fashion both for the Kantowski-Sachs and for the Bianchi-I models which are topologically completely different. Our results suggest that this behavior is intrinsic to the coupling of the Skyrme field to gravity rather than on a specific cosmological model.