Heterotic-Type I Dual Pairs, Rigid Branes and Broken Susy

TL;DR

This paper explores the duality between heterotic and type I string theories in various dimensions, focusing on moduli space structures, rigid branes, and supersymmetry breaking, demonstrating explicit dual pairs with reduced gauge group ranks.

Contribution

It constructs explicit heterotic-type I dual pairs in dimensions ≥5 with broken supersymmetry and reduced gauge group ranks, including analysis of moduli space and stability.

Findings

Dual pairs exist with gauge group reduced by 0, 8, or 16 units.

Moduli space components admit heterotic duals in dimensions ≥5.

Broken supersymmetry models are tachyon-free below the string scale.

Abstract

The moduli space of toroidal type I vacua, which are consistent at the non-perturbative level, consists of independent branches characterized by the number (0, 16 or 32) of rigid branes sitting on top of orientifold planes. This structure persists also when supersymmetry is spontaneously broken a la Scherk-Schwarz. We show that all the components of the moduli space in dimension $D\ge 5$ indeed admit heterotic dual components, by explicitly constructing heterotic-type I dual pairs with the rank of the gauge group reduced by 0, 8 or 16 units. In the presence of spontaneous breaking of supersymmetry, the dual pairs we consider are also free of tachyonic instabilities at the one-loop level, provided the scale of supersymmetry breaking is lower than the string scale.