Tachyon couplings on non-BPS D-branes and Dirac-Born-Infeld action

TL;DR

This paper computes specific string theory amplitudes involving tachyons on non-BPS D-branes, proposes an extended Dirac-Born-Infeld action incorporating tachyon dynamics, and generalizes it to non-abelian cases.

Contribution

It introduces a field theory action that reproduces string-derived tachyon couplings and extends the framework to non-abelian gauge groups.

Findings

Derived explicit tachyon couplings from string amplitudes.

Proposed an extended DBI action including tachyon fields.

Extended the action to non-abelian gauge theories.

Abstract

By explicit evaluation of certain disk S-matrix elements in the presence of background B-flux, we find coupling of two open string tachyons to gauge field, graviton, dilaton or Kalb-Ramond antisymmetric tensor on the world-volume of a single non-BPS D$p$-brane. We then propose an extension of the abelian Dirac-Born-Infeld action which naturally reproduces these couplings in field theory. This action includes non-linearly the dynamics of the tachyon field much like the other bosonic modes of the non-BPS D$p$-brane. On the general grounds of gauge and T-duality transformations and the symmetrized trace prescription, we then extend the abelian action to non-abelian cases.