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53
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
Spacetime Instanton Corrections in 4D String Vacua (The Seesaw Mechanism for DBrane Models)
, 2006
"... We systematically investigate instanton corrections from wrapped Euclidean Dbranes to the matter field superpotential of various classes of N=1 supersymmetric Dbrane models in four dimensions. Both gauge invariance and counting fermionic zero modes provide strong constraints on the allowed nonper ..."
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Cited by 136 (28 self)
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We systematically investigate instanton corrections from wrapped Euclidean Dbranes to the matter field superpotential of various classes of N=1 supersymmetric Dbrane models in four dimensions. Both gauge invariance and counting fermionic zero modes provide strong constraints on the allowed nonperturbative superpotential couplings. We outline how the complete instanton computation boils down to the computation of open string disc diagrams for boundary changing operators multiplied by a oneloop vacuum diagram. For concreteness we focus on E2instanton effects in Type IIA vacua with intersecting D6branes, however the same structure emerges for Type IIB and heterotic vacua. The instantons wrapping rigid cycles can potentially destabilise the vacuum or generate perturbatively absent matter couplings such as proton decay operators, µparameter or righthanded neutrino Majorana mass terms. The latter allow the realization of the seesaw mechanism for MSSM like intersecting Dbrane models.
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
Loopcorrected compactifications of the heterotic string with line bundles
, 2005
"... We consider the E8×E8 heterotic string theory compactified on CalabiYau manifolds with bundles containing abelian factors in their structure group. Generic low energy consequences such as the generalised GreenSchwarz mechanism for the multiple anomalous abelian gauge groups are studied. We also co ..."
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Cited by 84 (16 self)
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We consider the E8×E8 heterotic string theory compactified on CalabiYau manifolds with bundles containing abelian factors in their structure group. Generic low energy consequences such as the generalised GreenSchwarz mechanism for the multiple anomalous abelian gauge groups are studied. We also compute the holomorphic gauge couplings and induced FayetIliopoulos terms up to oneloop order, where the latter are interpreted as stringy oneloop corrections to the DonaldsonUhlenbeckYau condition. Such models generically have frozen combinations of Kähler and dilaton moduli. We study concrete bundles with structure group SU(N) × U(1) M yielding quasirealistic gauge groups with chiral matter given by certain bundle cohomology classes. We also provide a number of explicit tadpole free examples of bundles defined by exact sequences of sums of line bundles over complete intersection CalabiYau spaces. This includes one example with precisely the Standard Model gauge symmetry.
Distributions of Nonsupersymmetric Flux Vacua
, 2004
"... We continue the study of the distribution of nonsupersymmetric flux vacua in IIb string theory compactified on CalabiYau manifolds, as in hepth/0404116. We show that the basic structure of this problem is that of finding eigenvectors of the matrix of second derivatives of the superpotential, and t ..."
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Cited by 77 (9 self)
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We continue the study of the distribution of nonsupersymmetric flux vacua in IIb string theory compactified on CalabiYau manifolds, as in hepth/0404116. We show that the basic structure of this problem is that of finding eigenvectors of the matrix of second derivatives of the superpotential, and that many features of the results are determined by features of the generic ensemble of such matrices, the CI ensemble of Altland and Zirnbauer originating in mesoscopic physics. We study some simple examples in detail, exhibiting various factors which can favor low or high scale supersymmetry breaking.
Systematics of moduli stabilisation in CalabiYau flux compactifications
 JHEP
, 2005
"... We study the large volume limit of the scalar potential in CalabiYau flux compactifications of type IIB string theory. Under general circumstances there exists a limit in which the potential approaches zero from below, with an associated nonsupersymmetric AdS minimum at exponentially large volume. ..."
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Cited by 73 (15 self)
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We study the large volume limit of the scalar potential in CalabiYau flux compactifications of type IIB string theory. Under general circumstances there exists a limit in which the potential approaches zero from below, with an associated nonsupersymmetric AdS minimum at exponentially large volume. Both this and its de Sitter uplift are tachyonfree, thereby fixing all Kähler and complex structure moduli. Also, for the class of vacua described in this paper, the gravitino mass is independent of the flux discretuum, whereas the ratio of the string scale to the 4d Planck scale is hierarchically small but flux dependent. The inclusion of α ′ corrections plays a crucial role in the structure of the potential. We illustrate these ideas through explicit computations for a particular CalabiYau manifold.
One in a billion: MSSMlike Dbrane statistics
, 2005
"... Continuing our recent work hepth/0411173, we study the statistics of fourdimensional, supersymmetric intersecting Dbrane models in a toroidal orientifold background. We have performed a vast computer survey of solutions to the stringy consistency conditions and present their statistical implicatio ..."
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Cited by 66 (18 self)
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Continuing our recent work hepth/0411173, we study the statistics of fourdimensional, supersymmetric intersecting Dbrane models in a toroidal orientifold background. We have performed a vast computer survey of solutions to the stringy consistency conditions and present their statistical implications with special emphasis on the frequency of Standard Model features. Among the topics we discuss are the implications of the Ktheory constraints, statistical correlations among physical quantities and an investigation of the various statistical suppression factors arising once certain Standard Model features are required. We estimate the frequency of an MSSM like gauge group with three generations to be one in a billion.
Heterotic gut and standard model vacua from simply connected calabiyau manifolds
, 2006
"... We consider fourdimensional supersymmetric compactifications of the E8× E8 heterotic string on CalabiYau manifolds endowed with vector bundles with structure group SU(N) × U(1) and fivebranes. After evaluating the GreenSchwarz mechanism and deriving the generalized DonaldsonUhlenbeckYau condi ..."
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Cited by 61 (3 self)
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We consider fourdimensional supersymmetric compactifications of the E8× E8 heterotic string on CalabiYau manifolds endowed with vector bundles with structure group SU(N) × U(1) and fivebranes. After evaluating the GreenSchwarz mechanism and deriving the generalized DonaldsonUhlenbeckYau condition including the fivebrane moduli, we show that this construction can give rise to GUT models containing U(1) factors like flipped SU(5) or directly the Standard Model even on simply connected CalabiYau manifolds. Concrete realizations of threegeneration models on elliptically fibered CalabiYau manifolds are presented. They exhibit the most attractive features of flipped SU(5) models such as doublettriplet splitting and proton stability. In contrast to conventional GUT string models, the tree level relations among the Standard Model gauge couplings at the GUT scale are changed.
An open string landscape
 JHEP
, 2005
"... Abstract: The effect of fluxes on open string moduli is studied by analyzing the constraints imposed by supersymmetry on Dbranes in type IIB flux backgrounds. We show that generically the conditions of supersymmetry cannot be maintained when moving along the geometrical moduli space of the brane, s ..."
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Cited by 56 (3 self)
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Abstract: The effect of fluxes on open string moduli is studied by analyzing the constraints imposed by supersymmetry on Dbranes in type IIB flux backgrounds. We show that generically the conditions of supersymmetry cannot be maintained when moving along the geometrical moduli space of the brane, so that open string moduli are lifted. In specific examples, we find that there is a disconnected and discrete set of supersymmetric solutions to the open string equations of motion, which extends the familiar closed string landscape to the open string sector. Permanent addressContents
Chiral Dbrane models with frozen open string moduli
, 2005
"... Most intersecting Dbrane vacua in the literature contain additional massless adjoint fields in their low energy spectrum. The existence of these additional fields make it difficult to obtain negative beta functions and, eventually, asymptotic freedom. We address this important issue for N = 1 inter ..."
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Cited by 46 (14 self)
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Most intersecting Dbrane vacua in the literature contain additional massless adjoint fields in their low energy spectrum. The existence of these additional fields make it difficult to obtain negative beta functions and, eventually, asymptotic freedom. We address this important issue for N = 1 intersecting Dbrane models, rephrasing the problems in terms of (open string) moduli stabilization. In particular, we consider a Z2 × Z2 orientifold construction where D6branes wrap rigid 3cycles and such extra adjoint fields do not arise. We derive the model building rules and consistency conditions for intersecting branes in this background, and provide N = 1 chiral vacua free of adjoint fields. More precisely, we construct a PatiSalamlike model whose SU(4) gauge group is asymptotically free. We also comment on the application of these results for obtaining gaugino condensation in chiral Dbrane models. Finally, we embed our constructions in the framework of flux compactification, and construct new classes of N = 1 and N = 0 chiral flux vacua.