Some remarks on tachyon action in 2d string theory

TL;DR

This paper examines the effective tachyon action in 2D string theory, revealing nonlocality from cubic terms and questioning the validity of the standard cubic approximation at tree level.

Contribution

It demonstrates that the commonly used cubic tachyon action is insufficient and introduces the importance of nonlocal terms starting from cubic order.

Findings

Cubic terms in the tachyon action are nonlocal.

The standard cubic approximation does not reproduce correct amplitudes.

Four-point 1PI terms are analyzed in detail.

Abstract

We discuss the effective action of tachyon in the two dimensional string theory at tree level. We show that already starting from the cubic terms the action is nonlocal and the usually assumed simplest cubic term does not give the correct amplitude. Four point 1PI terms are also discussed.