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27
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
Largevolume flux compactifications: Moduli spectrum and D3/D7 soft supersymmetry breaking
 SYSTEMATICS OF MODULI STABILISATION IN CALABIYAU FLUX COMPACTIFICATIONS,” JHEP 0503 (2005) 007 [ARXIV:HEPTH/0502058]. – 42
, 2005
"... We present an explicit calculation of the spectrum of a general class of string models, corresponding to CalabiYau flux compactifications with h1,2> h1,1> 1 with leading perturbative and nonperturbative corrections, in which all geometric moduli are stabilised as in hepth/0502058. The volum ..."
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Cited by 129 (20 self)
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We present an explicit calculation of the spectrum of a general class of string models, corresponding to CalabiYau flux compactifications with h1,2> h1,1> 1 with leading perturbative and nonperturbative corrections, in which all geometric moduli are stabilised as in hepth/0502058. The volume is exponentially large, leading to a range of string scales from the Planck mass to the TeV scale, realising for the first time the large extra dimensions scenario in string theory. We provide a general analysis of the relevance of perturbative and nonperturbative effects and the regime of validity of the effective field theory. We compute the spectrum in the moduli sector finding a hierarchy of masses depending on inverse powers of the volume. We also compute soft supersymmetry breaking terms for particles living on D3 and D7 branes. We find a hierarchy of soft terms corresponding to ‘volume dominated ’ Fterm supersymmetry breaking. Fterms for Kähler moduli dominate both those for dilaton and complex
Proeyen, “Dirac actions for Dbranes on backgrounds with fluxes,” arXiv:hepth/0504041
"... The understanding of the fermionic sector of the worldvolume Dbrane dynamics on a general background with fluxes is crucial in several branches of string theory, like for example the study of nonperturbative effects or the construction of realistic models living on Dbranes. In this paper we derive ..."
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Cited by 45 (6 self)
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The understanding of the fermionic sector of the worldvolume Dbrane dynamics on a general background with fluxes is crucial in several branches of string theory, like for example the study of nonperturbative effects or the construction of realistic models living on Dbranes. In this paper we derive a new simple Diraclike form for the bilinear fermionic action for any Dpbrane in any supergravity background, which generalizes the usual Dirac action valid in absence of fluxes. A nonzero worldvolume field strength deforms the usual Dirac operator in the action to a generalized noncanonical one. We show how the canonical form can be reestablished by a redefinition of the worldvolume geometry.
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.
An inflaton mass problem in string inflation from threshold corrections to volume stabilization
 LETT. B
, 2005
"... Inflationary models whose vacuum energy arises from a Dterm are believed not to suffer from the supergravity eta problem of Fterm inflation. That is, Dterm models have the desirable property that the inflaton mass can naturally remain much smaller than the Hubble scale. We observe that this advan ..."
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Cited by 15 (1 self)
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Inflationary models whose vacuum energy arises from a Dterm are believed not to suffer from the supergravity eta problem of Fterm inflation. That is, Dterm models have the desirable property that the inflaton mass can naturally remain much smaller than the Hubble scale. We observe that this advantage is lost in models based on string compactifications whose volume is stabilized by a nonperturbative superpotential: the Fterm energy associated with volume stabilization causes the eta problem to reappear. Moreover, any shift symmetries introduced to protect the inflaton mass will typically be lifted by threshold corrections to the volumestabilizing superpotential. Using threshold corrections computed by Berg, Haack, and Körs, we illustrate this point in the example of the D3D7 inflationary model, and conclude that inflation is possible, but only for finetuned values of the stabilized moduli. More generally, we conclude that inflationary models in stable string compactifications, even Dterm models with shift symmetries, will require a certain amount of finetuning to avoid this new contribution to the eta problem
Aspects of Dbrane Dynamics in Supergravity Backgrounds with Fluxes, Kappa–symmetry and Equations of Motion. Part IIB
, 2006
"... We derive and carry out a detailed analysis of the equations of motion of the type IIB D branes in generic supergravity backgrounds with fluxes making account of the worldvolume Born–Infeld gauge field and putting a special emphasis on the structure of the Dirac equation for Dp brane fermionic modes ..."
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Cited by 12 (3 self)
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We derive and carry out a detailed analysis of the equations of motion of the type IIB D branes in generic supergravity backgrounds with fluxes making account of the worldvolume Born–Infeld gauge field and putting a special emphasis on the structure of the Dirac equation for Dp brane fermionic modes. We present an explicit form of the worldvolume field equations for each of the Dp branes (p = 1, 3, 5, 7, 9) in the cases in which the Neveu–Schwarz flux and the Ramond–Ramond p–form flux along the Dp–brane worldvolume are zero and the supergravity backgrounds do not necessarily induce the worldvolume Born–Infeld flux. We then give several examples of D3, D5 and D7 brane configurations in which the worldvolume Born–Infeld flux is intrinsically non–zero and therefore must be taken into account in studying problems where such branes are involved. The examples include D3 and D5 brane instantons carrying (self–dual) worldvolume gauge fields in warped compactification backgrounds.
Dbrane Instantons in Type II String Theory
, 2009
"... We review recent progress in determining the effects of Dbrane instantons in N = 1 supersymmetric compactifications of Type II string theory to four dimensions. We describe the abstract Dbrane instanton calculus for holomorphic couplings such as the superpotential, the gauge kinetic function and h ..."
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Cited by 3 (2 self)
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We review recent progress in determining the effects of Dbrane instantons in N = 1 supersymmetric compactifications of Type II string theory to four dimensions. We describe the abstract Dbrane instanton calculus for holomorphic couplings such as the superpotential, the gauge kinetic function and higher fermionic Fterms. This includes a discussion of multiinstanton effects and the implications of background fluxes for the instanton sector. Our presentation also highlights, but is not restricted to the computation of Dbrane instanton effects in quiver gauge theories on Dbranes at singularities. We then summarize the concrete consequences of stringy Dbrane instantons for the construction of semirealistic models of particle physics
hepth/0609013 Moduli Stabilization in Type IIB Orientifolds (II)
"... We discuss general properties of moduli stablization in KKLT scenarios in type IIB orientifold compactifications X6. In particular, we find conditions for the Kähler potential to allow a KKLT scenario for a manifold X6 without complex structure moduli, i.e. h(2,1)(X6) = 0. This way, a whole class o ..."
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We discuss general properties of moduli stablization in KKLT scenarios in type IIB orientifold compactifications X6. In particular, we find conditions for the Kähler potential to allow a KKLT scenario for a manifold X6 without complex structure moduli, i.e. h(2,1)(X6) = 0. This way, a whole class of type IIB orientifolds with h(2,1)(X6) = 0 is ruled out. This excludes in particular all ZN–and ZN ×ZM–orientifolds X6 with h(2,1)(X6) = 0 for a KKLT scenario. This concerns Z3,Z7,Z3 ×Z3,Z4 ×Z4,Z6 ×Z6 and Z2 ×Z6 ′ –both at the orbifold point and away from it. Furthermore, we propose a mechanism to stabilize the Kaehler moduli accociated to the odd cohomology H (1,1) − (X6). In the second part of this work we discuss the moduli stabilization of resolved type IIB ZN – or ZN ×ZM–orbifold/orientifold compactifications. As examples for the resolved Z6 and Z2 × Z4 orbifolds we fix all moduli through a combination of fluxes and racetrack superpotential. Contents 1. Introduction.............................
hepth/yymmnnn A Stringy Test of Flux–Induced Isometry Gauging
"... Supergravity analysis suggests that the effect of fluxes in string theory compactifications is to gauge isometries of the scalar manifold. However, isometries are generically broken by brane instanton effects. Here we demonstrate how fluxes protect exactly those isometries from quantum corrections w ..."
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Supergravity analysis suggests that the effect of fluxes in string theory compactifications is to gauge isometries of the scalar manifold. However, isometries are generically broken by brane instanton effects. Here we demonstrate how fluxes protect exactly those isometries from quantum corrections which are gauged according to the classical supergravity analysis. We also argue that all other isometries are generically broken. Submitted to Journal of High Energy Physics (JHEP)