paper

Non-perturbative Orientifolds

arXiv:hep-th/9904007 · doi:10.1016/S0370-2693(99)00485-2

Abstract

We consider non-perturbative six and four dimensional N=1 space-time supersymmetric orientifolds. Some states in such compactifications arise in ``twisted'' open string sectors which lack world-sheet description in terms of D-branes. Using Type I-heterotic duality we are able to obtain the massless spectra for some of such orientifolds. The four dimensional compactification we discuss in this context is an example of a chiral N=1 supersymmetric string vacuum which is non-perturbative in both orientifold and heterotic pictures. In particular, it contains both D9- and D5-branes plus non-perturbative ``twisted'' open string sector states as well.

13 pages, revtex, a minor misprint corrected (to appear in Phys. Lett. B)

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