Results 1  10
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56
Split States, Entropy Enigmas, Holes and Halos
, 2007
"... We investigate degeneracies of BPS states of Dbranes on compact CalabiYau manifolds. We develop a factorization formula for BPS indices using attractor flow trees associated to multicentered black hole bound states. This enables us to study background dependence of the BPS spectrum, to compute e ..."
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Cited by 235 (22 self)
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We investigate degeneracies of BPS states of Dbranes on compact CalabiYau manifolds. We develop a factorization formula for BPS indices using attractor flow trees associated to multicentered black hole bound states. This enables us to study background dependence of the BPS spectrum, to compute explicitly exact indices of various nontrivial Dbrane systems, and to clarify the subtle relation of DonaldsonThomas invariants to BPS indices of stable D6D2D0 states, realized in supergravity as “hole halos. ” We introduce a convergent generating function for D4 indices in the large CY volume limit, and prove it can be written as a modular average of its polar part, generalizing the fareytail expansion of the elliptic genus. We show polar states are “split ” D6antiD6 bound states, and that the partition function factorizes accordingly, leading to a refined version of the OSV conjecture. This differs from the original conjecture in several aspects. In particular we obtain a nontrivial measure factor g −2 top e−K and find factorization requires a cutoff. We show that the main factor determining the cutoff and therefore the error is the existence of “swing states ” — D6 states which exist at large radius but do not form stable D6antiD6 bound states. We point out a likely breakdown of the OSV conjecture at small gtop (in the large background CY volume limit), due to the surprising phenomenon that for sufficiently large background Kähler moduli, a charge ΛΓ supporting single centered black holes of entropy ∼ Λ2S(Γ) also admits twocentered BPS black hole realizations whose entropy grows like Λ3 when Λ → ∞.
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
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.
Lifting DInstanton Zero Modes by Recombination and Background Fluxes
, 2007
"... We study the conditions under which Dbrane instantons in Type II orientifold compactifications generate a nonperturbative superpotential. If the instanton is noninvariant under the orientifold action, it carries four instead of the two Goldstone fermions required for superpotential contributions. ..."
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Cited by 40 (15 self)
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We study the conditions under which Dbrane instantons in Type II orientifold compactifications generate a nonperturbative superpotential. If the instanton is noninvariant under the orientifold action, it carries four instead of the two Goldstone fermions required for superpotential contributions. Unless these are lifted, the instanton can at best generate higher fermionic Fterms of BeasleyWitten type. We analyse two strategies to lift the additional zero modes. First we discuss the process of instantonic brane recombination in Type IIA orientifolds. We show that in some cases charge invariance of the measure enforces the presence of further zero modes which, unlike the Goldstinos, cannot be absorbed. In other cases, the instanton exhibits reparameterisation zero modes after recombination and a superpotential is generated if these are lifted by suitable closed or open string couplings. In the second part of the paper we address lifting the extra Goldstinos of D3brane instantons by supersymmetric threeform background fluxes in Type IIB orientifolds. This requires nontrivial gauge flux on the instanton. Only if the part of the fermionic action linear in the gauge flux survives the orientifold projection can the extra Goldstinos be lifted.
A chiral cascade via backreacting D7branes with flux
, 2007
"... In the context of AdS/CFT, we consider a cascading theory with an arbitrarily large number of chiral flavors. In the UV the theory can be considered as a chiral flavoring of the KlebanovTseytlin solution, and exhibits a duality wall. Instead in the IR, due to the rich dynamics, it safely flows to a ..."
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Cited by 32 (2 self)
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In the context of AdS/CFT, we consider a cascading theory with an arbitrarily large number of chiral flavors. In the UV the theory can be considered as a chiral flavoring of the KlebanovTseytlin solution, and exhibits a duality wall. Instead in the IR, due to the rich dynamics, it safely flows to a noncascading theory. We engineer the field theory through intersecting D7branes with worldvolume gauge flux on a conifold with 3form fluxes, and we find new fully backreacted solutions of Type IIB Supergravity plus branes. We match the field theory cascade with supergravity by computing Page charges and interpreting Seiberg dualities as large gauge transformations of the background. Eventually we give an
D6branes and torsion
"... Abstract: The D6brane spectrum of type IIA vacua based on twisted tori ˜T 6 and RR background fluxes is analyzed. In particular, we compute the torsion factors of Hn(˜T 6, Z) and describe the effect that they have on D6brane physics. For instance, the fact that H3(˜T 6, Z) contains ZN subgroups ex ..."
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Cited by 31 (3 self)
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Abstract: The D6brane spectrum of type IIA vacua based on twisted tori ˜T 6 and RR background fluxes is analyzed. In particular, we compute the torsion factors of Hn(˜T 6, Z) and describe the effect that they have on D6brane physics. For instance, the fact that H3(˜T 6, Z) contains ZN subgroups explains why RR tadpole conditions are affected by geometric fluxes. In addition, the presence of torsional (co)homology shows why some D6brane moduli are lifted, and it suggests how the Dbrane discretum appears in type IIA flux compactifications. Finally, we give a clear, geometrical understanding of the FreedWitten anomaly in the present type IIA setup, and discuss its consequences for the construction of semirealistic flux vacua. Contents 1. Motivation and Summary
Symmetrybreaking vacua and baryon condensates in ads/cft
, 2008
"... We study the gravity duals of symmetrybreaking deformations of superconformal field theories, AdS/CFT dual to Type IIB string theory on AdS5 × Y where Y is a SasakiEinstein manifold. In these vacua both conformal invariance and baryonic symmetries are spontaneously broken. We present a detailed di ..."
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Cited by 26 (7 self)
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We study the gravity duals of symmetrybreaking deformations of superconformal field theories, AdS/CFT dual to Type IIB string theory on AdS5 × Y where Y is a SasakiEinstein manifold. In these vacua both conformal invariance and baryonic symmetries are spontaneously broken. We present a detailed discussion of the supergravity moduli space, which involves flat form fields on asymptotically conical CalabiYau manifolds, and match this to the gauge theory vacuum moduli space. We discuss certain linearised fluctuations of the moduli, identifying the Goldstone bosons associated with spontaneous breaking of nonanomalous baryonic symmetries. The remaining moduli fields are related to spontaneous breaking of anomalous baryonic symmetries. We also elaborate on the proposal that computing condensates of baryon operators is equivalent to computing the partition function of a noncompact Euclidean D3brane in the background supergravity
Flux algebra, Bianchi identities and FreedWitten . . .
, 2009
"... We discuss the structure of 4D gauged supergravity algebras corresponding to globally nongeometric compactifications of Ftheory, admitting a local geometric description in terms of 10D supergravity. By starting with the well known algebra of gauge generators associated to nongeometric type IIB flux ..."
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Cited by 25 (2 self)
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We discuss the structure of 4D gauged supergravity algebras corresponding to globally nongeometric compactifications of Ftheory, admitting a local geometric description in terms of 10D supergravity. By starting with the well known algebra of gauge generators associated to nongeometric type IIB fluxes, we derive a full algebra containing all, closed RR and NSNS, geometric and nongeometric dual fluxes. We achieve this generalization by a systematic application of SL(2, Z) duality transformations and by taking care of the spinorial structure of the fluxes. The resulting algebra encodes much information about the higher dimensional theory. In particular, tadpole equations and Bianchi identities are obtainable as Jacobi identities of the algebra. When a sector of magnetized (p,q) 7branes is included, certain closed axions are gauged by the U(1) transformations on the branes. We indicate how the diagonal gauge generators of the branes can be incorporated into the full algebra, and show that FreedWitten constraints and tadpole cancellation conditions for (p,q) 7branes can be described as Jacobi identities satisfied by the algebra mixing bulk and brane gauge generators.