Higher derivative corrections to WZ action: One RR, one NSNS and one NS couplings

TL;DR

This paper computes and analyzes higher derivative couplings involving one RR, one NSNS, and one NS field on D-branes, confirming consistency with string amplitudes and fixing unknown couplings via T-duality constraints.

Contribution

It provides the first detailed calculation of contact terms involving one RR, one NSNS, and one NS field at order α'^2, and uniquely determines the couplings using T-duality.

Findings

Confirmed consistency of amplitudes with known D-brane couplings.

Derived contact terms at order α'^2 involving RR, NSNS, and NS fields.

Fixed all unknown couplings using T-duality constraints.

Abstract

In the first part of this paper, we calculate the disk-level S-matrix elements of one RR, one NSNS and one NS vertex operators, and show that they are consistent with the amplitudes that have been recently found by applying various Ward identities. We show that the massless poles of the amplitude at low energy are fully consistent with the known D-brane couplings at order $\alpha'^2$ which involve one RR or NSNS and two NS fields. Subtracting the massless poles, we then find the contact terms of one RR, one NSNS and one NS fields at order $\alpha'^2$. Some of these terms are reproduced by the Taylor expansion and the pull-back of two closed string couplings, some other couplings are reproduced by linear graviton in the second fundamental form and by the B-field in the gauge field extension $F\rightarrow F+B$, in one closed and two open string couplings. In the second part, we write all independent covariant contractions of one RR, one NSNS and one NS fields with unknown coefficients. We then constrain the couplings to be consistent with the linear T-duality and with the above contact terms. Interestingly, we have found that up to total derivative terms and Bianchi identities, these constraints uniquely fix all the unknown coefficients.