Loss of Quantum Coherence and Positivity of Energy Density in Semiclassical Quantum Gravity

TL;DR

This paper investigates how quantum coherence is lost in semiclassical quantum gravity and demonstrates that energy density remains positive and consistent with classical physics in a non-static spacetime.

Contribution

It reveals the loss of quantum coherence due to gauge potentials and establishes the positivity of energy density in semiclassical quantum gravity.

Findings

Energy density loses quantum coherence in non-static spacetimes

Energy density remains positive in semiclassical quantum gravity

Classical Hamiltonian derived from energy density in coherent states

Abstract

In the semiclassical quantum gravity derived from the Wheeler-DeWitt equation, the energy density of a matter field loses quantum coherence due to the induced gauge potential from the parametric interaction with gravity in a non-static spacetime. It is further shown that the energy density takes only positive values and makes superposition principle hold true. By studying a minimal massive scalar field in a FRW spacetime background, we illustrate the positivity of energy density and obtain the classical Hamiltonian of a complex field from the energy density in coherent states.