On modified tachyon DBI action

TL;DR

This paper verifies a modified tachyon DBI action by calculating the superstring theory S-matrix for four tachyons and a gauge field, confirming the action's accuracy at low energies.

Contribution

It provides the first explicit string theory calculation that confirms the modified tachyon DBI action with internal CP matrices.

Findings

First and second order terms match the modified tachyon DBI action

Validates the proposed modification of the tachyon DBI action

Enhances understanding of tachyon dynamics in string theory

Abstract

Recently a modification of the tachyon DBI action has been proposed in which the tachyon carries the internal CP matrix \sigma_1 and \sigma_2. In this paper, we find the momentum expansion of the disk level S-matrix element of four tachyons and one gauge field in superstring theory and show that the first and second order terms of the expansion are in perfect agreement with the above tachyon DBI action.