Related papers: Magnetized (Shift-)Orientifolds
We study deformations of $Z_2 \times Z_2$ (shift-)orientifolds in four dimensions in the presence of both uniform Abelian internal magnetic fields and quantized NS-NS $B_{ab}$ backgrounds, that are shown to be equivalent to asymmetric…
I review the basic features of four dimensional Z_2 x Z_2 (shift) orientifolds with internal magnetic fields, describing two examples with N=1 supersymmetry. As in the corresponding six-dimensional examples, D9-branes magnetized along four…
We review orientifold constructions in the presence of magnetic backgrounds both in the open and closed sectors. Generically, the resulting orientifold models have a nice geometric description in terms of rotated D-branes and/or O-planes.…
Dualities between certain supersymmetric gauge field theories in three and four dimensions have been studied in considerable detail recently, by realizing them as geometric manipulations of configurations of extended objects in type II…
We discuss Z_2 \times Z_2 orientifolds where the orbifold twists are accompanied by shifts on momentum or winding lattice states. The models contain variable numbers of D5 branes, whose massless (and, at times, even massive) modes have…
We present special classes of orientifold models involving supersymmetry breaking via branes at angles. Type II superstring theories are compactified on a two torus times a four-dimensional orbifold. Combining worldsheet parity with a…
We construct N=1 supersymmetric four-dimensional orientifolds of type IIA on T^6/(Z_2 x Z_2) with D6-branes intersecting at angles. The use of D6-branes not fully aligned with the O6-planes in the model allows for a construction of many…
We study a new class of N=1 supersymmetric orientifolds in six space-time dimensions. The world-sheet parity transformation is combined with a permutation of the internal complex coordinates. In contrast to ordinary orientifolds the twisted…
We discuss some aspects of the physics of branes in the presence of orientifolds and the corresponding worldvolume gauge dynamics. We show that at strong coupling orientifolds sometimes turn into bound states of orientifolds and branes, and…
Recently, a D-brane construction in type IIA string theory was shown to yield the electric/magnetic duality of four dimensional N=1 supersymmetric U(N_c) gauge theories with N_f flavours of quark. We present here an extension of that…
D6-branes intersecting at angles allow for phenomenologically appealing constructions of four dimensional string theory vacua. While it is straightforward to obtain non-supersymmetric realizations of the standard model, supersymmetric and…
We consider four-dimensional N=1 field theories realized by type IIA brane configurations of NS-branes and D4-branes, in the presence of orientifold six-planes and D6-branes. These configurations are known to present interesting effects…
We investigate Z2 x Z2 orientifolds with group actions involving shifts. A complete classification of possible geometries is presented where also previous work by other authors is included in a unified framework from an intersecting D-brane…
We generalize the construction of four dimensional non-tachyonic orientifolds of type 0B string theory to non-supersymmetric backgrounds. We construct a four dimensional model containing self-dual D3 and D9-branes and leading to a chiral…
In the presence of internal magnetic fields, a D9 brane can acquire a D5 (or anti-D5) R-R charge, and can therefore contribute to the corresponding tadpole. In the resulting vacua, supersymmetry is generically broken and tachyonic…
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…
In this paper we study the N=1 supersymmetric field theories realized on the world-volume of type IIB D3-branes sitting at orientifolds of non-orbifold singularities (conifold and generalizations). Several chiral models belong to this…
We construct orientifolds of type IIA string theory. The theory is compactified on a T^6/Z_N times Z_M orbifold. In addition worldsheet parity in combination with a reflection of three compact directions is modded out. Tadpole cancellation…
Within the context of type I strings, we show the equivalence between BPS D9 branes with internal magnetic fluxes H_i in the three torii and non-BPS D3 branes with inverted internal magnetic fluxes 1/H_i. We then construct new…
This thesis contains an introductory chapter on orbifolds. The following chapter explains the foundations of orientifolds. Chapters 4-7 present own research. In chapter 4 we quantize open strings with linear boundary conditions, as they…