1998/04/30 by Zurab Kakushadze, Gary Shiu, S. -H. Henry Tye · 1 citation
Physics and Astronomy · #hep-th
paper · pdf · doi:10.1016/s0550-3213(98)00491-x
published as Nucl.Phys. B533 (1998) 25-87 · 62 pages, revtex, 2 figures, minor misprints corrected, references and acknowledgments added
arxiv created 1998/05/09 · arxiv updated 2009/11/30
We consider six and four dimensional \cal N=1 supersymmetric orientifolds of Type IIB compactified on orbifolds. We give the conditions under which the perturbative world-sheet orientifold approach is adequate, and list the four dimensional \cal N=1 orientifolds (which are rather constrained) that satisfy these conditions. We argue that in most cases orientifolds contain non-perturbative sectors that are missing in the world-sheet approach. These non-perturbative sectors can be thought of as arising from D-branes wrapping various collapsed 2-cycles in the orbifold. Using these observations, we explain certain ``puzzles'' in the literature on four dimensional orientifolds. In particular, in some four dimensional orientifolds the ``naive'' tadpole cancellation conditions have no solution. However, these tadpole cancellation conditions are derived using the world-sheet approach which we argue to be inadequate in these cases due to appearance of additional non-perturbative sectors. The main tools in our analyses are the map between F-theory and orientifold vacua and Type I-heterotic duality. Utilizing the consistency conditions we have found in this paper, we discuss consistent four dimensional chiral \cal N=1 Type I vacua which are non-perturbative from the heterotic viewpoint.