Classical and Quantum Shell Dynamics, and Vacuum Decay

TL;DR

This paper develops a reparametrization-invariant shell dynamics model from Einstein-Hilbert action, linking classical evolution with quantum tunneling and vacuum decay through a Hamiltonian constraint framework.

Contribution

It introduces a new reparametrization-invariant Lagrangian for shell dynamics derived from Einstein-Hilbert action, connecting classical and quantum descriptions including vacuum decay.

Findings

Reproduces Israel's matching condition in a simple gauge.

Formulates the Wheeler-DeWitt equation for shell states.

Analyzes quantum tunneling and vacuum decay via WKB approximation.

Abstract

Following a minisuperspace approach to the dynamics of a spherically symmetric shell, a reduced Lagrangian for the radial degree of freedom is derived directly from the Einstein-Hilbert action. The key feature of this new Lagrangian is its invariance under time reparametrization. Indeed, all classical and quantum dynamics is encoded in the Hamiltonian constraint that follows from that invariance. Thus, at the classical level, we show that the Hamiltonian constraint reproduces, in a simple gauge, Israel's matching condition which governs the evolution of the shell. In the quantum case, the vanishing of the Hamiltonian (in a weak sense), is interpreted as the Wheeler-DeWitt equation for the physical states, in analogy to the corresponding case in quantum cosmology. Using this equation, quantum tunneling through the classical barrier is then investigated in the WKB approximation, and the connection to vacuum decay is elucidated.