Semiclassical geometrodynamics of homogeneous cosmology

TL;DR

This paper investigates the classical-quantum hybrid dynamics of homogeneous cosmology, revealing how quantum backreaction influences late-time evolution and potential dark energy contributions, with exact solutions found for certain models.

Contribution

It introduces a Hamiltonian framework for classical-quantum hybrid cosmology and compares dynamics, highlighting quantum backreaction effects and exact static solutions in isotropic and anisotropic models.

Findings

Quantum backreaction affects late-time cosmological evolution.

Scalar energy density may contribute to dark energy.

Exact static solutions exist for certain cosmological models.

Abstract

We study the classical-quantum (CQ) hybrid dynamics of homogeneous cosmology from a Hamiltonian perspective where the classical gravitational phase space variables and matter state evolve self-consistently with full backreaction. We compare numerically the classical and CQ dynamics for isotropic and anisotropic models, including quantum scalar-field induced corrections to the Kasner exponents. Our results indicate that full backreaction effects leave traces at late times in cosmological evolution; in particular, the scalar energy density at late times provides a potential contribution to dark energy. We also show that the CQ equations admit exact static solutions for the isotropic, and the anisotropic Bianchi IX universes with the scalar field in a stationary state.