Effective Constraints and Physical Coherent States in Quantum Cosmology: A Numerical Comparison

TL;DR

This paper compares physical coherent state and effective constraint methods in quantum cosmology, demonstrating quantum back-reaction effects and analyzing their strengths and weaknesses in cyclic and radiation-filled models.

Contribution

It provides a detailed numerical comparison of two approaches in quantum cosmology, highlighting their effectiveness and limitations in different cosmological models.

Findings

Quantum back-reaction effects are clearly demonstrated.

Strengths and weaknesses of both methods are illustrated.

Effective constraints work in more realistic models without coherent states.

Abstract

A cosmological model with a cyclic interpretation is introduced, which is subject to quantum back-reaction and yet can be treated rather completely by physical coherent state as well as effective constraint techniques. By this comparison, the role of quantum back-reaction in quantum cosmology is unambiguously demonstrated. Also the complementary nature of strengths and weaknesses of the two procedures is illustrated. Finally, effective constraint techniques are applied to a more realistic model filled with radiation, where physical coherent states are not available.