RR-Dilaton Interaction in a Type IIB Superstring

TL;DR

This paper investigates the interaction between RR states and the dilaton in type IIB superstring theory, revealing that RR terms lack the usual dilaton factor and providing a geometric interpretation of this phenomenon.

Contribution

It constructs vertex operators for RR states and computes their correlation functions with the dilaton, deriving the low-energy effective action and its geometric implications.

Findings

RR terms in the effective action do not contain the standard dilaton factor

Spin operators in RR vertices reduce the Euler characteristic of the worldsheet by 1

An additional dilatonic term appears in the worldsheet action due to this effect

Abstract

We analyze the interaction between the massless RR states with a dilaton in a type IIB superstring. By constructing vertex operators for massless and massive RR states and computing their correlation functions with a dilaton we find the Ramond-Ramond part of the superstring low-energy effective action. The RR terms appearing in the action do not contain the standard dilatonic factor (string coupling constant). The geometrical interpretation of this fact is presented. Namely we argue that the spin operators in the RR vertices effectively decrease the Euler character of the worldsheet by 1 unit. As a result, the additional dilatonic term proportional to string coupling constant appears in the worldsheet string action.