# On Non-BPS Effective Actions of String Theory

## TL;DR

This paper analyzes the detailed structure of non-BPS effective actions in type IIA and IIB superstring theories, focusing on scattering amplitudes, Bianchi identities, and higher derivative corrections to understand their physical implications.

## Contribution

It provides a comprehensive calculation of non-BPS scattering amplitudes, including all singularities, contact terms, and higher derivative corrections, revealing universal features and consistency conditions.

## Key findings

- Derived all-order $\alpha'$ corrections to non-BPS amplitudes
- Established compatibility of amplitudes in different super-ghost pictures
- Identified universal higher derivative expansion in tachyon momenta

## Abstract

We discuss some physical prospective of the non-BPS effective actions of type IIA and IIB superstring theories. By dealing with the complete all three and four point functions, including a closed string Ramond-Ramond (in terms of both its field strength and its potential), gauge (scalar) fields as well as a real tachyon and under symmetry structures, we find various restricted world volume and bulk Bianchi identities. The complete forms of the non-BPS scattering amplitudes including their Chan-Paton factors are elaborated. All the singularity structures of the non-BPS amplitudes, their all orders $\alpha'$ higher derivative corrections, their contact terms and various modified Bianchi identities are derived. Finally we show that scattering amplitudes computed in different super-ghost pictures are compatible when suitable Bianchi identities are imposed on the Ramond-Ramond fields. Moreover, we argue that the higher derivative expansion in powers of the momenta of the tachyon is universal.