On the Four-Dimensional Effective Action of Strongly Coupled Heterotic String Theory

TL;DR

This paper explicitly computes the four-dimensional effective action of strongly coupled heterotic string theory, revealing that certain potentials remain unchanged while others receive significant corrections, advancing understanding of string compactifications.

Contribution

It provides the first detailed calculation of the Kahler potential, gauge kinetic functions, and matter terms in the strongly coupled heterotic string effective action, including nontrivial corrections.

Findings

Kahler potential matches weakly coupled theory to order kappa^{2/3}.

Gauge kinetic functions receive non-vanishing corrections at order kappa^{4/3}.

Nontrivial corrections to the dilaton term from background fields depending on the orbifold coordinate.

Abstract

The low-energy D=4, N=1 effective action of the strongly coupled heterotic string is explicitly computed by compactifying Horava-Witten theory on the deformed Calabi-Yau three-fold solution due to Witten. It is shown that, to order kappa^{2/3}, the Kahler potential is identical to that of the weakly coupled theory. Furthermore, the gauge kinetic functions are directly computed to order kappa^{4/3} and shown to receive a non-vanishing correction. Also, we compute gauge matter terms in the Kahler potential to the order kappa^{4/3} and find a nontrivial correction to the dilaton term. Part of those corrections arise from background fields that depend on the orbifold coordinate and are excited by four-dimensional gauge field source terms.