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56
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 InstantonToolbox for FTheory Model Building
"... Several dimensionful parameters needed for model building can be engineered in a certain class of SU(5) Ftheory GUTs by adding extra singlet fields which are localized along pairwise intersections of D7branes. The values of these parameters, however, depend on dynamics external to the GUT which ca ..."
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Cited by 36 (6 self)
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Several dimensionful parameters needed for model building can be engineered in a certain class of SU(5) Ftheory GUTs by adding extra singlet fields which are localized along pairwise intersections of D7branes. The values of these parameters, however, depend on dynamics external to the GUT which causes the singlets to acquire suitable masses or expectation values. In this note, we demonstrate that D3instantons which wrap the same 4cycle as one of the intersecting D7’s can provide precisely the needed dynamics to generate several important scales, including the supersymmetrybreaking scale and the righthanded neutrino mass. Furthermore, these instantons seem unable to directly generate the µ term suggesting that, at least in this class of models, it should perhaps be tied to one of the other scales in the problem. More specifically, we study the simple system consisting of a pair of D7branes wrapping del Pezzo surfaces which intersect along a curve Σ of genus 0 or 1 and classify all instanton configurations which can potentially contribute to the superpotential. This allows one to formulate topological conditions which must be imposed on Σ for various modelbuilding applications. Along the way, we also observe that the construction of [7]
Realistic Yukawa couplings through instantons in intersecting brane worlds
, 2007
"... The Yukawa couplings of the simpler models of Dbranes on toroidal orientifolds suffer from the socalled “rank one” problem – there is only a single nonzero mass and no mixing. We consider the oneloop contribution of E2instantons to Yukawa couplings on intersecting D6branes, and show that they c ..."
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Cited by 28 (1 self)
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The Yukawa couplings of the simpler models of Dbranes on toroidal orientifolds suffer from the socalled “rank one” problem – there is only a single nonzero mass and no mixing. We consider the oneloop contribution of E2instantons to Yukawa couplings on intersecting D6branes, and show that they can solve the rank one problem. In addition they have the potential to provide a geometric explanation for the hierarchies observed in the Yukawa coupling. In order to do this we provide
Realistic Yukawa structures from orientifold compactifications
, 2009
"... We perform a systematic analysis of globally consistent Dbrane quivers which realize the MSSM and analyze them with respect to their Yukawa couplings. Often, desired couplings are perturbatively forbidden due to the presence of global U(1) symmetries. We investigate the conditions under which Dbra ..."
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Cited by 25 (10 self)
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We perform a systematic analysis of globally consistent Dbrane quivers which realize the MSSM and analyze them with respect to their Yukawa couplings. Often, desired couplings are perturbatively forbidden due to the presence of global U(1) symmetries. We investigate the conditions under which Dbrane instantons will induce these missing couplings without generating other phenomenological drawbacks, such as Rparity violating couplings or a µterm which is too large. Furthermore, we systematically analyze which quivers allow for a mechanism that can account for the small neutrino masses and other experimentally observed hierarchies. We show that only a small fraction of the globally consistent Dbrane quivers
Unoriented Dbrane Instantons vs Heterotic Worldsheet Instantons
, 2007
"... We discuss Fermi interactions of four hyperini generated by “stringy” ..."
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Cited by 11 (5 self)
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We discuss Fermi interactions of four hyperini generated by “stringy”
Instanton Induced Neutrino Majorana Masses in CFT Orientifolds with MSSMlike spectra
, 2007
"... hepth/yymmnnn ..."
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Instanton Induced Open String Superpotentials and Branes at Singularities,” JHEP 02 (2008) 103, arXiv:0711.1316 [hepth
 35 I. GarciaEtxebarria and
"... We study different aspects of the nonperturbative superpotentials induced by Euclidean E3branes on systems of D3/D7branes located at Abelian orbifold singularities. We discuss in detail how the induced couplings are consistent with the U(1) symmetries carried by the D3/D7 branes. We construct dif ..."
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Cited by 8 (1 self)
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We study different aspects of the nonperturbative superpotentials induced by Euclidean E3branes on systems of D3/D7branes located at Abelian orbifold singularities. We discuss in detail how the induced couplings are consistent with the U(1) symmetries carried by the D3/D7 branes. We construct different compact and noncompact examples, and show phenomenologically relevant couplings like µterms or certain Yukawa couplings generated by these E3 instantons. Some other novel effects are described. We show an example where E3 instantons combine with standard gauge instantons to yield new multiinstanton effects contributing to superpotential, along the lines of ref.[28]. In the case of nonSUSY ZN tachyonfree singularities it is shown how E3instantons give rise to non Euclidean brane instantons (see e.g. [1]) provide the leading nonperturbative contribution to several important quantities in string compactifications. For instance Dbrane instantons in type II compactifications (or F/Mtheory duals) have led to (in some cases very explicit) proposals to lift 4d moduli which are otherwise flat directions of the theory
Power Towers of String Instantons for N=1 Vacua
, 2008
"... We provide arguments for the existence of novel hereinafter called polyinstanton corrections to holomorphic couplings in fourdimensional N=1 supersymmetric string compactifications. After refining quantitatively the Dbrane instanton calculus for corrections to the gauge kinetic function, we explic ..."
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Cited by 6 (2 self)
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We provide arguments for the existence of novel hereinafter called polyinstanton corrections to holomorphic couplings in fourdimensional N=1 supersymmetric string compactifications. After refining quantitatively the Dbrane instanton calculus for corrections to the gauge kinetic function, we explicitly apply it to the Type I toroidal orbifold defined in arXiv:0710.3080 and compare the results to the proposed heterotic Sdual model. This leads us to the intriguing conclusion that N=1 string vacua feature a power tower like proliferation of instanton corrections.
Instantons and Holomorphic Couplings in Intersecting Dbrane Models
, 2007
"... We clarify certain aspects and discuss extensions of the recently introduced string Dinstanton calculus (hepth/0609191). The oneloop determinants are related to oneloop open string threshold corrections in intersecting D6brane models. Utilising a nonrenormalisation theorem for the holomorphic W ..."
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Cited by 6 (2 self)
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We clarify certain aspects and discuss extensions of the recently introduced string Dinstanton calculus (hepth/0609191). The oneloop determinants are related to oneloop open string threshold corrections in intersecting D6brane models. Utilising a nonrenormalisation theorem for the holomorphic Wilsonian gauge kinetic functions, we derive a number of constraints for the moduli dependence of the matter field Kähler potentials of intersecting D6brane models on the torus. Moreover, we compute string oneloop corrections to the FayetIliopoulos terms on the D6branes finding that they are proportional to the gauge threshold corrections. Employing these results, we discuss the issue of holomorphy for E2instanton corrections to the superpotential. Eventually, we discuss E2instanton corrections to the gauge kinetic functions and the FIterms.
Gauge Thresholds and Kähler Metrics for Rigid Intersecting Dbrane Models
 JHEP
"... The gauge threshold corrections for globally consistent Z2 ×Z ′ 2 orientifolds with rigid intersecting D6branes are computed. The oneloop corrections to the holomorphic gauge kinetic function are extracted and the Kähler ..."
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Cited by 6 (0 self)
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The gauge threshold corrections for globally consistent Z2 ×Z ′ 2 orientifolds with rigid intersecting D6branes are computed. The oneloop corrections to the holomorphic gauge kinetic function are extracted and the Kähler