4D Spherically Symmetric Time-Dependent Quantum Gravity Amplitudes

TL;DR

This paper non-perturbatively computes time-dependent quantum gravity amplitudes in 4D spherically symmetric space-times, revealing non-unitary evolution generally, with a special case allowing unitarity.

Contribution

It introduces a novel method to solve classical and quantum constraints via a canonical transformation, enabling calculation of amplitudes without explicit path integral solutions.

Findings

Most boundary conditions lead to non-unitary evolution.

A special boundary condition case may allow unitary evolution.

Provides a new approach to quantum gravity amplitude calculations.

Abstract

In these short notes, we compute non-perturbatively the time-dependent quantum gravity amplitudes for a four-dimensional spherically symmetric space-time with space-like and time-like boundaries. We solve the 4D classical and quantum constraints in a novel way. We identify the classical solution of the constraints as a canonical transformation, where the integration constants are the new variables. We apply this canonical transformation to the path integral representation of the amplitudes we are interested in. This procedure allows us to get the time-dependent amplitudes from the path integral without solving it explicitly. From these amplitudes, we show that for most of the boundary conditions time evolution in quantum gravity is non-unitary. There is however a special case where unitary evolution could be achieved.