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30
Fourdimensional String Compactifications with DBranes, Orientifolds and Fluxes
"... This review article provides a pedagogical introduction into various classes of chiral string compactifications to four dimensions with Dbranes and fluxes. The main concern is to provide all necessary technical tools to explicitly construct fourdimensional orientifold vacua, with the final aim to ..."
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Cited by 147 (18 self)
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This review article provides a pedagogical introduction into various classes of chiral string compactifications to four dimensions with Dbranes and fluxes. The main concern is to provide all necessary technical tools to explicitly construct fourdimensional orientifold vacua, with the final aim to come as close as possible to the supersymmetric Standard Model. Furthermore, we outline the available methods to derive the resulting fourdimensional effective action. Finally, we summarize recent attempts to address the
Orientifolds of K3 and CalabiYau manifolds with intersecting Dbranes
 JHEP
"... We investigate orientifolds of type II string theory on K3 and CalabiYau 3folds with intersecting Dbranes wrapping special Lagrangian cycles. We determine quite generically the chiral massless spectrum in terms of topological invariants and discuss both orbifold examples and algebraic realization ..."
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Cited by 85 (16 self)
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We investigate orientifolds of type II string theory on K3 and CalabiYau 3folds with intersecting Dbranes wrapping special Lagrangian cycles. We determine quite generically the chiral massless spectrum in terms of topological invariants and discuss both orbifold examples and algebraic realizations in detail. Intriguingly, the developed techniques provide an elegant way to figure out the chiral sector of orientifold models without computing any explicit string partition function. As a new example we derive a nonsupersymmetric Standardlike Model from an orientifold of type IIA on the quintic CalabiYau 3fold with wrapped D6branes. In the case of supersymmetric intersecting brane models on CalabiYau manifolds we discuss the Dterm and Fterm potentials, the effective gauge couplings and the GreenSchwarz mechanism. The mirror symmetric formulation of this construction is provided within type IIB theory. We finally include a short discussion about the lift of these models from type IIB on K3 to Ftheory and from type IIA on CalabiYau 3folds to Mtheory on G2 manifolds. 06/2002
Yukawa couplings in intersecting Dbrane models
 JHEP
"... Abstract: We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kähler and open string mod ..."
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Cited by 76 (9 self)
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Abstract: We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kähler and open string moduli but not on the complex structure. They arise from worldsheet instanton corrections and are found to be given by products of complex Jacobi theta functions with characteristics. The Yukawa couplings for a particular intersecting brane configuration yielding the chiral spectrum of the MSSM are computed as an example. We also show how our methods can be extended to compute Yukawa couplings on certain classes of elliptically fibered CY manifolds which are mirror to complex cones over del Pezzo surfaces. We find that the Yukawa couplings in intersecting D6brane models have a mathematical interpretation in the context of homological mirror symmetry. In particular, the computation of such Yukawa couplings is related to the construction of
Moduli stabilization in chiral type IIB orientifold models with fluxes
, 2003
"... We consider Type IIB orientifold models on CalabiYau spaces with threeform Gflux turned on. These fluxes freeze some of the complex structure moduli and the complex dilaton via an Fterm scalar potential. By introducing pairs of D9D9 branes with abelian magnetic fluxes it is possible to freeze a ..."
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Cited by 70 (11 self)
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We consider Type IIB orientifold models on CalabiYau spaces with threeform Gflux turned on. These fluxes freeze some of the complex structure moduli and the complex dilaton via an Fterm scalar potential. By introducing pairs of D9D9 branes with abelian magnetic fluxes it is possible to freeze also some of the Kähler moduli via a Dterm potential. Moreover, such magnetic fluxes in general lead to chiral fermions, which make them interesting for string modelbuilding. These issues are demonstrated in a simple toy model based on a Z2 × Z ′ 2 orbifold.
Supersymmetric intersecting branes on the type IIA T 6 /Z(4) orientifold
, 2003
"... We study supersymmetric intersecting D6branes wrapping 3cycles in the Type IIA T 6 / Z4 orientifold background. As a new feature, the 3cycles in this orbifold space arise both from the untwisted and the Z2 twisted sectors. We present an integral basis for the homology lattice, H3(M, Z), in terms ..."
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Cited by 52 (15 self)
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We study supersymmetric intersecting D6branes wrapping 3cycles in the Type IIA T 6 / Z4 orientifold background. As a new feature, the 3cycles in this orbifold space arise both from the untwisted and the Z2 twisted sectors. We present an integral basis for the homology lattice, H3(M, Z), in terms of fractional 3cycles, for which the intersection form involves the Cartan matrix of E8. We show that these fractional D6branes can be used to construct supersymmetric brane configurations realizing a three generation PatiSalam model. Via brane recombination processes preserving supersymmetry, this GUT model can be broken down to a standardlike model.
Gauge unification in supersymmetric intersecting brane worlds
 JHEP
"... We show that contrary to first expectations realistic three generation supersymmetric intersecting brane world models give rise to phenomenologically interesting predictions about gauge coupling unification. Assuming the most economical way of realizing the matter content of the MSSM via intersectin ..."
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Cited by 36 (8 self)
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We show that contrary to first expectations realistic three generation supersymmetric intersecting brane world models give rise to phenomenologically interesting predictions about gauge coupling unification. Assuming the most economical way of realizing the matter content of the MSSM via intersecting branes we obtain a model independent relation among the three gauge coupling constants at the string scale. In order to correctly reproduce the experimentally known values of sin 2 θw(Mz) and αs(Mz) this relation leads to natural gauge coupling unification at a string scale close to the standard GUT scale 2 × 10 16 GeV. Additional vectorlike matter can push the unification scale up to the Planck scale. 05/2003
New Standard Model Vacua from Intersecting Branes, JHEP
 Intersecting Brane Worlds on Tori and Orbifolds, Fortsch. Phys
"... We construct new D6brane model vacua (nonsupersymmetric) that have at low energy exactly the standard model spectrum (with right handed neutrinos). The minimal version of these models requires five stacks of branes. and the construction is based on D6branes intersecting at angles in D = 4 type to ..."
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Cited by 34 (12 self)
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We construct new D6brane model vacua (nonsupersymmetric) that have at low energy exactly the standard model spectrum (with right handed neutrinos). The minimal version of these models requires five stacks of branes. and the construction is based on D6branes intersecting at angles in D = 4 type toroidal orientifolds of type I strings. Three U(1)’s become massive through their couplings to RR couplings and from the two surviving anomaly free U(1)’s, one is the standard model hypercharge generator while the extra anomaly free U(1) could be broken from its nonzero couplings to RR fields and also by triggering a vev to previously massive particles. We suggest that extra massless U(1)’s should be broken by requiring some intersection to respect N = 1 supersymmetry thus supporting the appearance of massless charged singlets at the supersymmetric intersection. Proton is stable as baryon number is gauged and its anomalies are cancelled through a generalized GreenSchwarz mechanism. Neutrinos are of Dirac type with small masses, as in the four stack standard models of hepth/0105155, as a result of the existence of a similar PQ likesymmetry. The models are unique in the sense that they predict the existence of only one supersymmetric particle, the superpartner of νR.
Exact Standard model Structures from Intersecting D5branes
"... I discuss two types of nonsupersymmetric string model constructions that give at low energy exactly the Standard model (SM) with no additional matter/and or gauge group factors. The construction is based on D6 branes intersecting at angles in a compactification of type IIA theory on a decomposable ..."
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Cited by 33 (10 self)
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I discuss two types of nonsupersymmetric string model constructions that give at low energy exactly the Standard model (SM) with no additional matter/and or gauge group factors. The construction is based on D6 branes intersecting at angles in a compactification of type IIA theory on a decomposable orientifolded T 6 torus. The first type is based on five and six stack SMlike constructions at the string scale while, the other construction is based on a four stack GUT leftright symmetric structure centered around the PatiSalam SU(4)C × SU(2)L × SU(2)R gauge group. All classes of models exbibit important phenomenological properties including a stable proton and sizes of neutrino masses in consistency with neutrino oscillation experiments. The models are nonSUSY, but amazingly, they allow the existence of supersymmetric particles! 1.
Effective action and soft supersymmetry breaking for intersecting Dbrane models
"... We consider a generic scenario of spontaneous breaking of supersymmetry in the hidden sector within N = 1 supersymmetric orientifold compactifications of type II string theories with Dbranes that support semirealistic chiral gauge theories. The soft breaking terms in the visible sector of the mode ..."
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Cited by 30 (4 self)
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We consider a generic scenario of spontaneous breaking of supersymmetry in the hidden sector within N = 1 supersymmetric orientifold compactifications of type II string theories with Dbranes that support semirealistic chiral gauge theories. The soft breaking terms in the visible sector of the models are computed in a standard way without specifying the breaking mechanism, which leads to expressions that generalize those formerly known for heterotic or type I string models. The elements of the effective tree level supergravity action relevant for this, such as the Kähler metric for the matter fields, the superpotential of the visible sector and the gauge kinetic functions, are specified by dimensional reduction and duality arguments. As phenomenological applications we argue that gauge coupling unification can only occur in special regions of the moduli space; we show that flavor changing neutral currents can be suppressed sufficiently for a wide range of parameters, and we briefly address the issues of CP violation, electric dipole moments and dark matter, as well. 1