Off-shell extension of S-matrix elements and tachyonic effective actions

TL;DR

This paper develops an off-shell extension of superstring S-matrix elements involving scalars and tachyons, demonstrating consistency with the tachyonic Dirac-Born-Infeld effective action at low energies.

Contribution

It introduces a novel off-shell extension of superstring S-matrix elements that aligns with tachyonic DBI actions, enhancing understanding of string interactions beyond on-shell conditions.

Findings

Off-shell S-matrix elements are uniquely expressed.

Extensions are consistent with low-energy tachyonic DBI action.

Results unify string scattering amplitudes with effective field theories.

Abstract

We show that the on-shell S-matrix elements of four open string massless scalars, two scalars and two tachyons, and four open string tachyons in the super string theory can be written in a unique form. We then propose an off-shell extension for the S-matrix element of four scalars which is consistent, in the low energy limit, with the Dirac-Born-Infeld effective action. Using a similar off-shell extension for the S-matrix element of two scalars and two tachyons and for the S-matrix element of four tachyons, we show that they are fully consistent with the tachyonic DBI action.