Results 1  10
of
20
Generalized nonsupersymmetric flux vacua
, 2008
"... We discuss a novel strategy to construct 4D N = 0 stable flux vacua of type II string theory, based on the existence of BPS bounds for probe Dbranes in some of these backgrounds. In particular, we consider compactifications where Dbranes filling the 4D spacetime obey the same BPS bound as they ..."
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Cited by 45 (11 self)
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We discuss a novel strategy to construct 4D N = 0 stable flux vacua of type II string theory, based on the existence of BPS bounds for probe Dbranes in some of these backgrounds. In particular, we consider compactifications where Dbranes filling the 4D spacetime obey the same BPS bound as they would in an N = 1 compactification, while other Dbranes, like those appearing as domain walls from the 4D perspective, can no longer be BPS. We construct a subfamily of such backgrounds giving rise to 4D N = 0 Minkowski noscale vacua, generalizing the wellknown case of type IIB on a warped CalabiYau. We provide several explicit examples of these constructions, and compute quantities of phenomenological interest like fluxinduced soft terms on Dbranes. Our results have a natural, simple description in the language of Generalized Complex Geometry, and in particular in terms of Dbrane generalized calibrations. Finally, we extend the integrability theorems for 10D supersymmetric type II backgrounds to the N = 0 case and use the results to construct a new class of N = 0 AdS4 compactifications.
Hints for OffShell Mirror Symmetry in type II/Ftheory Compactifications
, 2009
"... We perform a Hodge theoretic study of parameter dependent families of Dbranes on compact Calabi–Yau manifolds in type II and Ftheory compactifications. Starting from a geometric GaussManin connection for B type branes we study the integrability and flatness conditions. The B model geometry define ..."
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Cited by 24 (4 self)
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We perform a Hodge theoretic study of parameter dependent families of Dbranes on compact Calabi–Yau manifolds in type II and Ftheory compactifications. Starting from a geometric GaussManin connection for B type branes we study the integrability and flatness conditions. The B model geometry defines an interesting ring structure of operators. For the mirror A model this indicates the existence of an openstring extension of the socalled A model connection, whereas the discovered ring structure should be part of the openstring A model quantum cohomology. We obtain predictions for genuine OoguriVafa invariants for Lagrangian branes on the quintic in P 4 that pass some nontrivial consistency checks. We discuss the lift of the brane compactifications to Ftheory on Calabi–Yau 4folds and the effective couplings in the effective supergravity action as determined by the N = 1 special geometry of the openclosed deformation space.
Gaugino Condensates and Dterms from D7branes
, 2006
"... We investigate, at the microscopic level, the compatibility between Dterm potentials from worldvolume fluxes on D7branes and nonperturbative superpotentials arising from gaugino condensation on a different stack of D7branes. This is motivated by attempts to construct metastable de Sitter vacua ..."
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Cited by 15 (1 self)
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We investigate, at the microscopic level, the compatibility between Dterm potentials from worldvolume fluxes on D7branes and nonperturbative superpotentials arising from gaugino condensation on a different stack of D7branes. This is motivated by attempts to construct metastable de Sitter vacua in type IIB string theory via Dterm uplifts. We find a condition under which the Kähler modulus, T, of a CalabiYau 4cycle gets charged under the anomalous U(1) on the branes with flux. If in addition this 4cycle is wrapped by a stack of D7branes on which gaugino condensation takes place, the question of U(1)gauge invariance of the (Tdependent) nonperturbative superpotential arises. In this case an index theorem guarantees that strings, stretching between the two stacks, yield additional charged chiral fields which also appear in the superpotential from gaugino condensation. We check that the charges work out to make this superpotential gauge invariant, and we argue that the mechanism survives the inclusion of higher curvature corrections to the D7brane action.
DBranes on generalized N = 1 backgrounds: superpotentials and Dterms
 JHEP 0606
"... We study the dynamics governing spacetime filling Dbranes on Type II flux backgrounds preserving fourdimensional N = 1 supersymmetry. The fourdimensional superpotentials and Dterms are derived. The analysis is kept on completely general grounds thanks to the use of recently proposed generalized ..."
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Cited by 11 (1 self)
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We study the dynamics governing spacetime filling Dbranes on Type II flux backgrounds preserving fourdimensional N = 1 supersymmetry. The fourdimensional superpotentials and Dterms are derived. The analysis is kept on completely general grounds thanks to the use of recently proposed generalized calibrations, which also allow one to show the direct link of the superpotentials and Dterms with BPS domain walls and cosmic strings respectively. In particular, our Dbrane setting reproduces the tension of Dterm strings found from purely fourdimensional analysis. The holomorphicity of the superpotentials is also studied and a moment map associated to the Dterms is proposed. Among different examples, we discuss an application to the study of D7branes on SU(3)structure backgrounds, which reproduces and generalizes some previous results.
Towards a realistic type IIA T 6 /Z4 orientifold model with background fluxes. I: Moduli stabilization
 J. High Energy Phys
"... We apply the methods of DeWolfe et al. [hepth/0505160] to a T 6 /Z4 orientifold model. This is the first step in an attempt to build a phenomenologically interesting metastable de There have been some longstanding, unsolved problems when it comes to realistic model building within the framework of ..."
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Cited by 2 (1 self)
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We apply the methods of DeWolfe et al. [hepth/0505160] to a T 6 /Z4 orientifold model. This is the first step in an attempt to build a phenomenologically interesting metastable de There have been some longstanding, unsolved problems when it comes to realistic model building within the framework of CalabiYau (CY) compactifications of superstring theories, namely • supersymmetry breaking,
Update of D3/D7Brane Inflation on K3 . . .
, 2008
"... We update the D3/D7brane inflation model on K3×T 2 /Z2 with branes and fluxes. For this purpose, we study the low energy theory including gs corrections to the gaugino condensate superpotential that stabilizes the K3 volume modulus. The gauge kinetic function is verified to become holomorphic when ..."
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We update the D3/D7brane inflation model on K3×T 2 /Z2 with branes and fluxes. For this purpose, we study the low energy theory including gs corrections to the gaugino condensate superpotential that stabilizes the K3 volume modulus. The gauge kinetic function is verified to become holomorphic when the original N = 2 supersymmetry is spontaneously broken to N = 1 by bulk fluxes. From the underlying classical N = 2 supergravity, the theory inherits a shift symmetry which provides the inflaton with a naturally flat potential. We analyze the fate of this shift symmetry after the inclusion of quantum corrections. The field range of the inflaton is found to depend significantly on the complex structure of the torus but is independent of its volume. This allows for a large kinematical field range for the inflaton. Furthermore, we show that the D3/D7 model may lead to a realization of the recent CMB fit by Hindmarsh et al. with an 11 % contribution from cosmic strings and a spectral index close to ns = 1. On the other hand, by a slight change of the parameters of the model one can strongly suppress the cosmic string contribution and reduce the spectral index ns to fit the WMAP5 data in the absence of cosmic strings. We also demonstrate that the inclusion of quantum corrections allows for a regime of eternal D3/D7 inflation.
STRING THEORY LANDSCAPE AND THE STANDARD MODEL OF PARTICLE PHYSICS
, 2007
"... In this paper we describe ideas about the string landscape, and how to relate it to the physics of the Standard Model of particle physics. First, we give a short status report about heterotic string compactifications. Then we focus on the statistics of Dbrane models, on the problem of moduli stabil ..."
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In this paper we describe ideas about the string landscape, and how to relate it to the physics of the Standard Model of particle physics. First, we give a short status report about heterotic string compactifications. Then we focus on the statistics of Dbrane models, on the problem of moduli stabilization, and finally on some attempts to derive a probability wave function in moduli space, which goes beyond the purely statistical count of string vacua.
D7Brane Motion from MTheory Cycles and Obstructions in the Weak Coupling Limit
, 801
"... Motivated by the desire to do proper model building with D7branes and fluxes, we study the motion of D7branes on a CalabiYau orientifold from the perspective of Ftheory. We consider this approach promising since, by working effectively with an elliptically fibred Mtheory compactification, the e ..."
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Motivated by the desire to do proper model building with D7branes and fluxes, we study the motion of D7branes on a CalabiYau orientifold from the perspective of Ftheory. We consider this approach promising since, by working effectively with an elliptically fibred Mtheory compactification, the explicit positioning of D7branes by (Mtheory) fluxes is straightforward. The locations of D7branes are encoded in the periods of certain Mtheory cycles, which allows for a very explicit understanding of the moduli space of D7brane motion. The picture of moving D7branes on a fixed underlying space relies on negligible backreaction, which can be ensured in Sen’s weak coupling limit. However, even in this limit we find certain ‘physics obstructions ’ which reduce the freedom of the D7brane motion as compared to the motion of holomorphic submanifolds in the orientifold background. These obstructions originate in the intersections of D7branes and O7planes, where the type IIB coupling cannot remain weak. We illustrate this effect for D7brane models on CP 1 × CP 1 (the BianchiSagnottiGimonPolchinski model) and on CP 2. Furthermore, in the simple example of 16 D7branes and 4 O7planes on CP 1
Open String Wavefunctions in Warped
, 812
"... Abstract: We analyze the wavefunctions for open strings in warped compactifications, and compute the warped Kähler potential for the light modes of a probe Dbrane. This analysis not only applies to the dynamics of Dbranes in warped backgrounds, but also allows to deduce warping corrections to the ..."
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Abstract: We analyze the wavefunctions for open strings in warped compactifications, and compute the warped Kähler potential for the light modes of a probe Dbrane. This analysis not only applies to the dynamics of Dbranes in warped backgrounds, but also allows to deduce warping corrections to the closed string Kähler metrics via their couplings to open strings. We consider in particular the spectrum of D7branes in warped CalabiYau orientifolds, which provide a string theory realizations of the RandallSundrum scenario. We find that certain background fluxes, necessary in the presence of warping, couple to the fermionic wavefunctions and qualitatively change their behavior. This modified dependence of the wavefunctions are needed for consistency with supersymmetry, though it is present in nonsupersymmetric vacua as well. We discuss the deviations of our setup from the RS scenario and, as an application of our results, compute the warping corrections to Yukawa couplings in a simple model. Our analysis is performed both with and without the presence of Dbrane worldvolume flux, as well as for the case of backgrounds with varying dilaton.