Target-Space Duality in Heterotic and Type I Effective Lagrangians

TL;DR

This paper investigates how target-space duality symmetries influence low-energy effective actions in different string theories, highlighting differences between heterotic and type IIB orientifolds and exploring constraints on effective Lagrangians.

Contribution

It demonstrates the incorporation of target-space duality in heterotic orbifold models and discusses obstructions in type IIB orientifolds, advancing understanding of string dualities at the effective action level.

Findings

Target-space duality can be incorporated in heterotic orbifold models.

Obstructions prevent similar duality incorporation in type IIB orientifolds.

Duality symmetries impose constraints on effective Lagrangians.

Abstract

We study the implications of target-space duality symmetries for low-energy effective actions of various four-dimensional string theories. In the heterotic case such symmetries can be incorporated in simple orbifold examples. At present a similar statement cannot be made about the simplest type IIB orientifolds due to an obstruction at the level of gravitational anomalies. This fact confirms previous doubts concerning a conjectured heterotic-type IIB orientifold duality and shows that target-space symmetries can be a powerful tool in studying relations between various string theories at the level of the effective low-energy action. Contraints on effective Lagrangians from these symmetries are discussed in detail. In particular, we consider ways of extending T-duality to include additional corrections to the Kaehler potential in heterotic string models with N=2 subsectors.