Moduli Corrections to Gravitational Couplings from String loops

TL;DR

This paper investigates how string loop corrections affect gravitational couplings in heterotic string compactifications, focusing on moduli dependence and deriving trace anomaly coefficients.

Contribution

It extends previous work on gauge couplings to gravitational couplings, providing a detailed analysis of moduli-dependent threshold corrections in heterotic strings.

Findings

Threshold corrections originate solely from the spacetime N=2 sector.

Derived trace anomaly coefficients for fields coupled to gravity.

Extended understanding of moduli effects on gravitational couplings.

Abstract

We study moduli dependent threshold corrections to gravitational couplings in the case of the heterotic string compactified on a symmetric orbifold, for untwisted moduli, extending previous analysis on gauge couplings. Like in the gauge case, the contribution comes entirely from the spacetime $N=2$ sector. As a byproduct, this calculation provides a simple derivation of the trace anomaly coefficients for the different fields coupled to gravity.