First-order quantum-gravitational correction to Friedmannian cosmology from covariant, holomorphic spinfoam cosmology

TL;DR

This paper derives a first-order quantum-gravitational correction to Friedmann cosmology from a holomorphic spinfoam model, revealing a small decelerating effect on the universe's expansion due to quantum effects.

Contribution

It introduces a novel quantum correction to Friedmann dynamics from covariant loop quantum gravity, applicable to homogeneous, isotropic cosmological models.

Findings

Quantum correction induces a small decelerating expansion.

Robustness of correction confirmed for various boundary graph refinements.

Mathematical links established between quantum cosmology and classical fluid/scalar field theories.

Abstract

The first-order loop quantum gravity correction of the simplest, classical general-relativistic Friedmann Hamiltonian constraint, emerging from a holomorphic spinfoam cosmological model peaked on homogeneous, isotropic geometries, is studied. The quantum Hamiltonian constraint, satisfied by the EPRL transition amplitude between the boundary cosmological coherent states, includes a contribution of the order of the Planck constant $\hbar$ that also appears in the corresponding semiclassical symplectic model. The analysis of this term gives a quantum-gravitational correction to the classical Friedmann dynamics of the scale factor yielding a small decelerating expansion (small accelerating contraction) of the universe. The robustness of the physical interpretation is established for arbitrary refinements of the boundary graphs. Also, mathematical equivalences between the semiclassical cosmological model and certain classical fluid and scalar field theories are explored.