S-matrix elements and covariant tachyon action in type 0 theory

TL;DR

This paper computes specific S-matrix elements in type 0 string theory and derives a covariant tachyon action, revealing which couplings are present or absent at leading order.

Contribution

It provides explicit calculations of S-matrix elements involving tachyons and massless states in type 0 theory and derives the corresponding covariant tachyon action.

Findings

Leading order terms match a covariant tachyon action.

No $T^4$, $T^2( abla T)^2$, $T^2H^2$, or $T^2R$ couplings at this order.

Non-zero couplings include $F\bar{F} T$ and $T^2 F^2$.

Abstract

We evaluate the sphere level S-matrix element of two tachyons and two massless NS states, the S-matrix element of four tachyons, and the S-matrix element of two tachyons and two Ramon-Ramond vertex operators, in type 0 theory. We then find an expansion for theses amplitudes that their leading order terms correspond to a covariant tachyon action. To the order considered, there are no $T^4$, $T^2(\prt T)^2$, $T^2H^2$, nor $T^2R$ tachyon couplings, whereas, the tachyon couplings $F\bF T$ and $T^2F^2$ are non-zero.