Classical and Quantum Shell Dynamics, and Vacuum Decay ¹

S.Ansoldi²
Dipartimento di Fisica Teorica dell'Università,
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste
Strada Costiera 11, 34014-Trieste, Italy

A.Aurilia³
Department of Physics, California State Polytechnic University
Pomona, CA 91768, USA

R.Balbinot⁴
Dipartimento di Fisica dell'Università
Istituto Nazionale di Fisica Nucleare, Sezione di Bologna,
via Irnerio 46, 40126-Bologna, Italy

E.Spallucci⁵
Dipartimento di Fisica Teorica dell'Università,
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste,
Strada Costiera 11, 34014-Trieste, Italy

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.