Quantum coherent dynamics of quasiclassical spacetimes

TL;DR

This paper introduces a Hamiltonian formalism for quantum gravity using coherent states to describe quasiclassical spacetimes, enabling analysis of their quantum dynamics and implications for black hole evaporation.

Contribution

It develops a new framework for gravitational dynamics in the coherent state basis, allowing for the study of superpositions and tunneling between geometries in quantum gravity.

Findings

Framework models superpositions of geometries dynamically.

Provides a mechanism for tunneling between different spacetime configurations.

Offers insights into unitarity preservation in black hole evaporation.

Abstract

In a wide range of quantum gravity theories, quasiclassical geometries, which are solutions to the Einstein field equations approximately, are described by "coherent states." Here we propose a Hamiltonian formalism for gravitational dynamics with respect to this coherent state basis, which generates time evolution of the spacetime with respect to a clock at infinity. Since the coherent states are not orthogonal, an initial quasiclassical geometry is dynamically driven into a superposition of different amplitudes. Our framework provides a dynamical mechanism for tunneling between geometries that is ubiquitous in a number of approaches to quantum gravity, from loop quantum gravity to the Euclidean path integral. We apply our framework to the problem of black hole evaporation, providing a hint at how unitarity may be preserved with the inclusion of quantum corrections to the semiclassical evolution of the black hole.