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377
Hierarchies from Fluxes in String Compactifications
, 2002
"... Warped compactifications with significant warping provide one of the few known mechanisms for naturally generating large hierarchies of physical scales. We demonstrate that this mechanism is realizable in string theory, and give examples involving orientifold compactifications of IIB string theory a ..."
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Cited by 715 (33 self)
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Warped compactifications with significant warping provide one of the few known mechanisms for naturally generating large hierarchies of physical scales. We demonstrate that this mechanism is realizable in string theory, and give examples involving orientifold compactifications of IIB string theory and Ftheory compactifications on CalabiYau fourfolds. In each case, the hierarchy of scales is fixed by a choice of RR and NS fluxes in the compact manifold. Our solutions involve compactifications of the KlebanovStrassler gravity dual to a confining N = 1 supersymmetric gauge theory, and the hierarchy reflects the small scale of chiral symmetry breaking in the dual gauge theory.
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
Topological sigmamodels with Hflux and twisted generalized complex manifolds
, 2008
"... We study the topological sector of N = 2 sigmamodels with Hflux. It has been known for a long time that the targetspace geometry of these theories is not Kähler and can be described in terms of a pair of complex structures, which do not commute, in general, and are parallel with respect to two di ..."
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Cited by 88 (4 self)
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We study the topological sector of N = 2 sigmamodels with Hflux. It has been known for a long time that the targetspace geometry of these theories is not Kähler and can be described in terms of a pair of complex structures, which do not commute, in general, and are parallel with respect to two different connections with torsion. Recently an alternative description of this geometry was found, which involves a pair of commuting twisted generalized complex structures on the target space. In this paper we define and study the analogues of A and Bmodels for N = 2 sigmamodels with Hflux and show that the results are naturally expressed in the language of twisted generalized complex geometry. For example, the space of topological observables is given by the cohomology of a Lie algebroid associated to one of the two twisted generalized complex structures. We determine the topological scalar product, which endows the algebra of observables with the structure of a Frobenius algebra. We also discuss mirror symmetry for twisted generalized CalabiYau manifolds.
BPS Action and Superpotential for Heterotic String Compactifications with Fluxes
, 2003
"... We consider N = 1 compactifications to four dimensions of heterotic string theory in the presence of fluxes. We show that up to order O (α ′2) the associated action can be written as a sum of squares of BPSlike quantities. In this way we prove that the equations of motion are solved by backgrounds ..."
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Cited by 81 (4 self)
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We consider N = 1 compactifications to four dimensions of heterotic string theory in the presence of fluxes. We show that up to order O (α ′2) the associated action can be written as a sum of squares of BPSlike quantities. In this way we prove that the equations of motion are solved by backgrounds which fulfill the supersymmetry conditions and the Bianchi identities. We also argue for the expression of the related superpotential and discuss the radial modulus
Dynamics of warped compactifications and the shape of the warped landscape
, 2005
"... The dynamics of warped/flux compactifications is studied, including warping effects, providing a firmer footing for investigation of the “landscape.” We present a general formula for the fourdimensional potential of warped compactifications in terms of tendimensional quantities. This allows a syste ..."
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Cited by 77 (2 self)
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The dynamics of warped/flux compactifications is studied, including warping effects, providing a firmer footing for investigation of the “landscape.” We present a general formula for the fourdimensional potential of warped compactifications in terms of tendimensional quantities. This allows a systematic investigation of modulifixing effects and potentials for mobile branes. We provide a necessary criterion, “slopedominance, ” for evading “nogo ” results for de Sitter vacua. We outline the tendimensional derivation of the nonperturbative effects that should accomplish this in KKLT examples, and outline a systematic discussion of their corrections. We show that potentials for mobile branes receive generic contributions inhibiting slowroll inflation. We give a linearized analysis of general scalar perturbations of warped IIB compactifications, revealing new features for both time independent and dependent moduli, and new aspects of the kinetic part of the fourdimensional effective action. The universal Kahler modulus is found not to be a simple scaling of the internal metric, and a prescription is given for defining holomorphic Kahler moduli, including warping effects. In the presence of mobile branes, this
Energy in generic higher curvature gravity theories,” Phys
 Rev. D
"... We define and compute the energy of higher curvature gravity theories in arbitrary dimensions. Generically, these theories admit constant curvature vacua (even in the absence of an explicit cosmological constant), and asymptotically constant curvature solutions with nontrivial energy properties. Fo ..."
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Cited by 70 (2 self)
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We define and compute the energy of higher curvature gravity theories in arbitrary dimensions. Generically, these theories admit constant curvature vacua (even in the absence of an explicit cosmological constant), and asymptotically constant curvature solutions with nontrivial energy properties. For concreteness, we study quadratic curvature models in detail. Among them, the one whose action is the square of the traceless Ricci tensor always has zero energy, unlike conformal (Weyl) gravity. We also study the stringinspired EinsteinGaussBonnet model and show that both its flat and AntideSitter vacua are stable. 1
String propagation in the presence of cosmological singularities, JHEP 0206
, 2002
"... We study string propagation in a spacetime with positive cosmological constant, which includes a circle whose radius approaches a finite value as t  → ∞, and goes to zero at t = 0. Near this cosmological singularity, the spacetime looks like IR 1,1 / Z. In string theory, this spacetime must be ex ..."
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Cited by 67 (2 self)
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We study string propagation in a spacetime with positive cosmological constant, which includes a circle whose radius approaches a finite value as t  → ∞, and goes to zero at t = 0. Near this cosmological singularity, the spacetime looks like IR 1,1 / Z. In string theory, this spacetime must be extended by including four additional regions, two of which are compact. The other two introduce new asymptotic regions, corresponding to early and late times, respectively. States of quantum fields in this spacetime are defined in the tensor product of the two Hilbert spaces corresponding to the early time asymptotic regions, and the Smatrix describes the evolution of such states to states in the tensor product of the two late time asymptotic regions. We show that string theory provides a unique continuation of wavefunctions past the cosmological singularities, and allows one to compute the Smatrix. The incoming vacuum evolves into an outgoing state with particles. We also discuss instabilities of asymptotically timelike linear dilaton spacetimes, and the question of holography in such spaces. Finally, we briefly comment on the relation of our results to recent discussions of de Sitter space.
A nogo theorem for string warped compactifications
, 2000
"... We give necessary conditions for the existence of perturbative heterotic and type II string warped compactifications preserving eight and four supersymmetries to four spacetime dimensions, respectively. In particular, we find that the only compactifications of heterotic string with the spin connecti ..."
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Cited by 60 (21 self)
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We give necessary conditions for the existence of perturbative heterotic and type II string warped compactifications preserving eight and four supersymmetries to four spacetime dimensions, respectively. In particular, we find that the only compactifications of heterotic string with the spin connection embedded in the gauge connection and type II strings are those on CalabiYau manifolds with constant dilaton. We obtain similar results for compactifications to six and to two dimensions.
New string vacua from twistor spaces
 PHYS REV. D
, 2008
"... We find a new family of AdS4 vacua in IIA string theory. The internal space is topologically either the complex projective space CP3 or the “flag manifold” SU(3)/(U(1)×U(1)), but the metric is in general neither Einstein nor Kähler. All known moduli are stabilized by fluxes, without using quantum ef ..."
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Cited by 55 (1 self)
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We find a new family of AdS4 vacua in IIA string theory. The internal space is topologically either the complex projective space CP3 or the “flag manifold” SU(3)/(U(1)×U(1)), but the metric is in general neither Einstein nor Kähler. All known moduli are stabilized by fluxes, without using quantum effects or orientifold planes. The analysis is completely