Strings from Orientifolds

TL;DR

This work constructs two-dimensional string vacua with chiral (0,N) supersymmetry by orientifolding Type IIB on T^8 with Z_2^n (n=1,2,3). It systematically derives the closed- and open-string spectra, analyzes tadpole cancellation, and solves Chan-Paton matrices to obtain consistent gauge and matter content that cancel the two-dimensional gravitational anomaly. Through detailed sector-by-sector accounting, the authors realize (0,8), (0,4), and (0,2) supersymmetric models with rich D-brane and orientifold plane configurations, and demonstrate their internal consistency. The results illuminate how chiral 2D vacua arise from orientifold constructions and connect to broader nonperturbative frameworks such as F-theory and M-theory. These models offer a controlled arena to study anomaly cancellation, brane dynamics, and the dynamics of low-dimensional cosmic strings within string theory.

Abstract

We construct models in 1+1 dimensions with chiral (0,N) supersymmetry by taking orientifolds of type IIB on an eight-torus identified by different numbers of reflections. The resulting models have Dirichlet strings, fivebranes and ninebranes stretched along different directions. The cases we study in detail have residual chiral supersymmetry (0,8), (0,4) and (0,2). The gravitational anomaly in all cases is shown to cancel.