Freely acting orbifolds of type IIB string theory on $T^5$

TL;DR

This paper explores freely acting orbifolds of type IIB string theory on T^5, constructing modular invariant partition functions, including new non-supersymmetric examples, and analyzing their supergravity limits and landscape of vacua.

Contribution

It introduces new examples of asymmetric orbifolds with modular invariance and explores their supergravity limits, expanding the landscape of string vacua with broken supersymmetry.

Findings

Constructed modular invariant partition functions for orbifolds.

Presented new non-supersymmetric, tachyon-free string models.

Identified constraints on supergravity spectra and orbifold sectors.

Abstract

We study freely acting orbifolds of type IIB string theory on $T^5$ that spontaneously break supersymmetry from $\mathcal{N}=8$ to $\mathcal{N}=6,4,2$ or 0 in five dimensions. We focus on orbifolds that are a $\mathbb{Z}_p$ quotient by a T-duality acting on $T^4$ and a shift on the remaining $S^1$. Modular invariant partition functions are constructed and detailed examples of both symmetric and asymmetric orbifolds are presented, including new examples of five-dimensional non-supersymmetric string theories with no tachyons. The orbifolds we consider arise at special points in the moduli space of string theory compactifications with a duality twist. The supergravity limit of these are Scherk-Schwarz reductions which generate gauged supergravities with positive definite potentials on the moduli space in five dimensions. Both symmetric and asymmetric freely acting orbifolds give a landscape of Minkowski vacua. For gauged supergravities to belong to this landscape, we find a number of constraints and conditions. Firstly, the scalar potential should lead to a massive spectrum with masses that obey quantization conditions arising from a string theory orbifold, which we discuss in detail. Secondly, we find constraints on the massless sector, e.g. in the examples of orbifolds preserving sixteen supercharges in five dimensions that we consider, only an odd number of vector multiplets arise. Lastly, we present new examples of candidate asymmetric orbifolds with modular invariant partition functions, but with non-integral coefficients in the $q\bar{q}$-expansion in the twisted sector.