Critical solutions of nonminimally coupled scalar field theory and first-order thermodynamics of gravity

TL;DR

This paper investigates critical solutions in nonminimally coupled scalar field cosmology and discusses their instability, challenging the applicability of first-order thermodynamics in scalar-tensor gravity models.

Contribution

It identifies unstable critical solutions in nonminimally coupled scalar field cosmology and examines their implications for the thermodynamics of gravity.

Findings

Critical solutions are unstable under homogeneous perturbations.

Unphysical nature of these solutions questions the thermodynamic formalism.

Highlights limitations of first-order thermodynamics in scalar-tensor theories.

Abstract

Analytical solutions of nonminimally coupled scalar field cosmology corresponding to critical scalar field values constitute a potential challenge to the recent first-order thermodynamics of scalar-tensor gravity (a formalism picturing general relativity as the zero-temperature equilibrium state for modified gravity). The critical solutions are unstable with respect to homogeneous perturbations, hence unphysical.