Semiclassical Tunneling in 1+1 Dimensional String Theory

TL;DR

This paper analyzes time-dependent tunneling phenomena in 1+1 dimensional string theory, using classical solutions and instanton methods to understand the non-perturbative effects and their dependence on the string coupling.

Contribution

It introduces a novel instanton approach to tunneling in 1+1D string theory, connecting classical Fermi sea solutions with quantum tunneling amplitudes and boundary contributions.

Findings

Tunneling amplitude behaves as exp(-C/g) with boundary contributions.

A unifying prescription connects Fermi levels above and below the barrier.

The approach relates to recent work by Brustein and Ovrut.

Abstract

We describe time-dependent tunneling of massless particles in 1+1 dimensional string field theory. Polchinski's description of the classical solutions in terms of the Fermi sea is used to identify the leading instanton contribution connecting the two half-lines. The field theory lagrangian is proportional to $1/g^2$, where $g$ is the string coupling constant, but the $S$-matrix for tunneling from one half-line to the other behaves as $\exp(-C/g)$. We note the constant~$C$ involves curious boundary contributions and observe that a prescription connecting the two half-lines unifies treatments of the Fermi level above and below the barrier. We also note the relation to recent work of Brustein and Ovrut.