Partial breaking of supersymmetry, open strings and M-theory

TL;DR

The paper analyzes spontaneous supersymmetry breaking in type I string vacua using freely acting orbifolds and Scherk-Schwarz deformations, distinguishing momentum vs winding implementations and leveraging heterotic/M-theory dualities. It constructs explicit 4d chiral models with $N=1\to 0$ breaking and various partial breakings $N=4\to N=2$ or $N=1$ in both closed and open sectors, accompanied by detailed one-loop amplitudes and tadpole constraints. The results illuminate how mass splittings scale with the compactification scale for branes aligned with the breaking and how chirality and gauge structure emerge in fully or partially broken vacua, with dual descriptions linking perturbative and non-perturbative regimes. These constructions provide a framework for chiral, softly broken SUSY vacua with potential phenomenological relevance and guide future explorations of radiative effects and effective field theories in M-theory/brane contexts.

Abstract

We study total and partial supersymmetry breaking by freely acting orbifolds, or equivalently by Scherk-Schwarz compactifications, in type I string theory. In particular, we describe a four-dimensional chiral compactification with spontaneously broken N=1 supersymmetry, some models with partial $N=4\to N=2$ and $N=4\to N=1$ supersymmetry breaking and their heterotic and M-theory duals. A generic feature of these models is that in the gravitational sector and in the spectrum of D-branes parallel to the breaking coordinate, all mass splittings are proportional to the compactification scale, while global (extended) supersymmetry remains unbroken at tree level for the massless excitations of D-branes transverse to the breaking direction.