Orientifolds of Non-Supersymmetric Asymmetric Orbifolds

TL;DR

The paper studies orientifolds of four-dimensional, asymmetric Z2 x Z2 orbifolds in type II string theory where worldsheet parity is gauged to yield non-oriented and open-string sectors. It shows that Dp and D(p-4) branes (or anti-D(p-4)) can be identified under the asymmetries, yielding brane bound states, with bulk and brane supersymmetry potentially differing (N=0 or N=2 in the bulk, N=2 on branes). The authors perform a full one-loop analysis (Klein bottle, cylinder, Möbius strip) and demonstrate tadpole cancellation and vanishing cosmological constant at one loop in these models, with open-string spectra exhibiting non-abelian gauge structures and N=2 supersymmetry on the branes. They discuss potential dual descriptions and phenomenological implications, including connections to Scherk-Schwarz-like supersymmetry breaking and non-perturbative duals.

Abstract

We consider certain four dimensional supersymmetric and non-supersymmetric asymmetric orbifolds with vanishing cosmological constant up to two loops and gauge the world sheet parity transformation. This leads to new string vacua, in which Dp and D(p-4) branes or Dp and anti-D(p-4) are identified. Moreover, it is shown that different degrees of supersymmetry can be realized in the bulk and on the brane. We show that for non-supersymmetric models the cosmological constant still vanishes at one loop order.

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