Gauge Invariant Action for the Open Bosonic String

TL;DR

This paper develops a gauge invariant action for the open bosonic string using the loop variable formalism, connecting it with tachyon potentials and revealing amplitude structures.

Contribution

It introduces a gauge invariant action formulation for the open bosonic string by modifying the loop variable formalism and resumming expansions to analyze amplitude structures.

Findings

Derived a gauge invariant action for open bosonic strings.

Connected the action to tachyon potential similar to background independent approaches.

Revealed pole structures in string amplitudes through resummation techniques.

Abstract

The issue of space time gauge invariance for the bosonic string has been earlier addressed using the loop variable formalism. In this paper the question of obtaining a gauge invariant action for the open bosonic string is discussed. The derivative w.r.t $ln a$ (where $a$ is a world sheet cutoff) of the partition function - which is first normalized by dividing by the integral of the two point function of a marginal operator - is a candidate for the action. Applied to the zero-momentum tachyon it gives a tachyon potential that is similar to those that have been obtained using Witten's background independent formalism. This procedure is easily made gauge invariant in the loop variable formalism by replacing $ln a$ by $\Sigma$ which is the generalization of the Liouville mode that occurs in this formalism. We also describe a method of resumming the Taylor expansion that is done in the loop variable formalism. This allows one to see the pole structure of string amplitudes that would not be visible in the original loop variable formalism.