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

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 Ramond–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 ( ∂ T ) 2 , T 2 H 2 , nor T 2 R tachyon couplings, whereas, the tachyon couplings F F ¯ T and T 2 F 2 are non-zero.