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114
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
Towards inflation in string theory
 JCAP
, 2003
"... We investigate the embedding of brane inflation into stable compactifications of string theory. At first sight a warped compactification geometry seems to produce a naturally flat inflaton potential, evading one wellknown difficulty of braneantibrane scenarios. Careful consideration of the closed ..."
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Cited by 82 (9 self)
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We investigate the embedding of brane inflation into stable compactifications of string theory. At first sight a warped compactification geometry seems to produce a naturally flat inflaton potential, evading one wellknown difficulty of braneantibrane scenarios. Careful consideration of the closed string moduli reveals a further obstacle: superpotential stabilization of the compactification volume typically modifies the inflaton potential and renders it too steep for inflation. We discuss the nongeneric conditions under which this problem does not arise. We conclude that brane inflation models can only work if restrictive assumptions about the method of volume stabilization, the warping of the internal space, and the source of inflationary energy are satisfied. We argue that this may not be a real problem, given the large range of available fluxes and background geometries in string theory.
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.
Moduli Stabilisation versus Chirality for MSSM like Type
 IIB Orientifolds,” JHEP 01 (2008) 058
"... We investigate the general question of implementing a chiral MSSM like Dbrane sector in Type IIB orientifold models with complete moduli stabilisation via Fterms induced by fluxes and spacetime instantons, respectively gaugino condensates. The prototype examples are the KKLT and the socalled lar ..."
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Cited by 62 (8 self)
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We investigate the general question of implementing a chiral MSSM like Dbrane sector in Type IIB orientifold models with complete moduli stabilisation via Fterms induced by fluxes and spacetime instantons, respectively gaugino condensates. The prototype examples are the KKLT and the socalled large volume compactifications. We show that the ansatz of first stabilising all moduli via Fterms and then introducing the Standard Model module is misleading, as a chiral sector notoriously influences the structure of nonperturbative effects and induces a Dterm potential. Focusing for concreteness on the large volume scenario, we work out the geometry of the swisscheese type CalabiYau manifold IP [1,3,3,3,5][15] (3,75) and analyse whether controllable and phenomenologically acceptable Kähler moduli stabilisation can occur by the combination of F and Dterms. Contents
The Statistics of Supersymmetric Dbrane Models
, 2004
"... We investigate the statistics of the phenomenologically important Dbrane sector of string compactifications. In particular for the class of intersecting Dbrane models, we generalise methods known from number theory to determine the asymptotic statistical distribution of solutions to the tadpole ca ..."
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Cited by 53 (21 self)
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We investigate the statistics of the phenomenologically important Dbrane sector of string compactifications. In particular for the class of intersecting Dbrane models, we generalise methods known from number theory to determine the asymptotic statistical distribution of solutions to the tadpole cancellation conditions. Our approach allows us to compute the statistical distribution of gauge theoretic observables like the rank of the gauge group, the number of chiral generations or the probability of an SU(N) gauge factor. Concretely, we study the statistics of intersecting branes on T 2 and T 4 / Z2 and T 6 / Z2 × Z2 orientifolds. Intriguingly, we find a statistical correlation between the rank of the gauge group and the number of chiral generations. Finally, we combine the statistics of the gauge theory sector with the statistics of the flux sector and study how distributions of gauge theoretic quantities are affected.
Enumerating Flux Vacua with Enhanced Symmetries
, 2004
"... We study properties of flux vacua in type IIB string theory in several simple but illustrative models. We initiate the study of the relative frequencies of vacua with vanishing superpotential W = 0 and with certain discrete symmetries. For the models we investigate we also compute the overall rate o ..."
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Cited by 52 (7 self)
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We study properties of flux vacua in type IIB string theory in several simple but illustrative models. We initiate the study of the relative frequencies of vacua with vanishing superpotential W = 0 and with certain discrete symmetries. For the models we investigate we also compute the overall rate of growth of the number of vacua as a function of the D3brane charge associated to the fluxes, and the distribution of vacua on the moduli space. The latter two questions can also be addressed by the statistical theory developed by Ashok, Denef and Douglas, and our results are in good agreement with their predictions. Analysis of the first two questions requires methods which are more numbertheoretic in nature. We develop some elementary techniques of this type, which are based on arithmetic properties of the periods of the compactification geometry at the points in moduli space where the flux vacua are located.
String cosmology
"... Abstract: We derive the corrections to the Friedmann equation of order ρ 2 in the RandallSundrum (RS) model, where two 3branes bound a slice of fivedimensional AntideSitter space. The effects of radion stabilization by the GoldbergerWise mechanism are taken into account. Surprisingly, we find t ..."
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Cited by 48 (2 self)
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Abstract: We derive the corrections to the Friedmann equation of order ρ 2 in the RandallSundrum (RS) model, where two 3branes bound a slice of fivedimensional AntideSitter space. The effects of radion stabilization by the GoldbergerWise mechanism are taken into account. Surprisingly, we find that an inflaton on either brane will experience no order ρ 2 corrections in the Hubble rate H due to its own energy density, although an observer on the opposite brane does see such a correction. Thus there is no enhancement of the slowroll condition unless inflation is simultaneously driven by inflatons on both branes. Similarly, during radiation domination, the ρ 2 correction to H on a given brane vanish unless there is nonvanishing energy density on the opposite brane. During the electroweak phase transition the correction can be large, but is has the wrong sign for causing sphalerons to go out of thermal equilibrium, so it cannot help electroweak baryogenesis. We discuss the differences
Nonperturbative superpotentials in Ftheory and string duality
, 2005
"... We use openclosed string duality between Ftheory on K3 × K3 and type II strings on CY manifolds without branes to study nonperturbative superpotentials in generalized flux compactifications. On the Ftheory side we obtain the full flux potential including D3instanton contributions and show that ..."
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Cited by 45 (2 self)
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We use openclosed string duality between Ftheory on K3 × K3 and type II strings on CY manifolds without branes to study nonperturbative superpotentials in generalized flux compactifications. On the Ftheory side we obtain the full flux potential including D3instanton contributions and show that it leads to an explicit and simple realization of the three ingredients of the KKLT model for stringy dS vacua. The D3instanton contribution is highly nontrivial, can be systematically computed including the determinant factors and demonstrates that a particular flux lifts very effectively zero modes on the instanton. On the closed string side, we describe a generalization of the GukovVafaWitten superpotential for type II strings on generalized CY manifolds, depending on all moduli multiplets.
Jumping Through Loops: On Soft Terms from Large Volume Compactifications
 JHEP
, 2007
"... We subject the phenomenologically successful large volume scenario of hepth/0502058 to a first consistency check in string theory. In particular, we consider whether the expansion of the string effective action is consistent in the presence of Dbranes and Oplanes. Due to the noscale structure at ..."
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Cited by 41 (0 self)
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We subject the phenomenologically successful large volume scenario of hepth/0502058 to a first consistency check in string theory. In particular, we consider whether the expansion of the string effective action is consistent in the presence of Dbranes and Oplanes. Due to the noscale structure at treelevel, the scenario is surprisingly robust. We compute the modification of soft supersymmetry breaking terms, and find only subleading corrections. We also comment that for largevolume limits of toroidal orientifolds and fibered CalabiYau manifolds the corrections can be more important,