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158
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
Building a better racetrack
 JHEP 0406
"... We find IIb compactifications on CalabiYau orientifolds in which all Kähler moduli are stabilized, along lines suggested by Kachru, Kallosh, Linde and Trivedi. ..."
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Cited by 114 (8 self)
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We find IIb compactifications on CalabiYau orientifolds in which all Kähler moduli are stabilized, along lines suggested by Kachru, Kallosh, Linde and Trivedi.
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 scaling of the noscale potential and de Sitter model building
"... We propose a variant of the KKLT (A)dS flux vacuum construction which does not require an antibrane to source the volume modulus. The strategy is to find nonzero local minima of the noscale potential in the complex structure and dilaton directions in moduli space. The corresponding noscale potenti ..."
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Cited by 61 (3 self)
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We propose a variant of the KKLT (A)dS flux vacuum construction which does not require an antibrane to source the volume modulus. The strategy is to find nonzero local minima of the noscale potential in the complex structure and dilaton directions in moduli space. The corresponding noscale potential expanded about this point sources the volume modulus in the same way as does the antibrane of the KKLT construction. We exhibit explicit examples of such nonzero local minima of the noscale potential in a simple toroidal orientifold model.
Proeyen, FayetIliopoulos terms in supergravity and cosmology
"... We clarify the structure of N = 1 supergravity in 1+3 dimensions with constant Fayet–Iliopoulos (FI) terms. The FI terms gξ induce nonvanishing Rcharges for the fermions and the superpotential. Therefore the Dterm inflation model in supergravity with constant FI terms has to be revisited. We pres ..."
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Cited by 59 (3 self)
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We clarify the structure of N = 1 supergravity in 1+3 dimensions with constant Fayet–Iliopoulos (FI) terms. The FI terms gξ induce nonvanishing Rcharges for the fermions and the superpotential. Therefore the Dterm inflation model in supergravity with constant FI terms has to be revisited. We present all corrections of order gξ/M 2 P to the classical supergravity action required by local supersymmetry and provide a gaugeanomalyfree version of the model. We also investigate the case of the socalled anomalous U(1) when a chiral superfield is shifted under U(1). In such a case, in the context of string theory, the FI terms originate from the derivative of the Kähler potential and they are inevitably fielddependent. This raises an issue of stabilization of the relevant field in applications to cosmology. The recently suggested equivalence between the Dterm strings and Dbranes of type II theory shows that braneantibrane systems produce FI terms in the effective 4d theory, with the RamondRamond axion shifting under the U(1) symmetry. This connection gives the possibility to interpret many unknown properties of D− ¯ D systems in the more familiar language of 4d supergravity Dterms, and vice versa. For instance, the shift of the axion field in both cases restricts the possible
Realistic Dbrane Models on Warped Throats: Fluxes, Hierarchies and Moduli Stabilization,” hepth/0312051; 27 Cascales and
 Chiral 4d N = 1 String Vacua with DBranes and NSNS and RR Fluxes,” JHEP 0305 (2003) 011, hepth/0303024
"... Abstract: We describe the construction of string theory models with semirealistic spectrum in a sector of (anti) D3branes located at an orbifold singularity at the bottom of a highly warped throat geometry, which is a generalisation of the KlebanovStrassler deformed conifold. These models realise ..."
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Cited by 56 (10 self)
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Abstract: We describe the construction of string theory models with semirealistic spectrum in a sector of (anti) D3branes located at an orbifold singularity at the bottom of a highly warped throat geometry, which is a generalisation of the KlebanovStrassler deformed conifold. These models realise the RandallSundrum proposal to naturally generate the Planck/electroweak hierarchy in a concrete string theory embedding, and yielding interesting chiral open string spectra. We describe examples with Standard Model gauge group (or leftright symmetric extensions) and three families of SM fermions, with correct quantum numbers including hypercharge. The dilaton and complex structure moduli of the geometry are stabilised by the 3form fluxes required to build the throat. We describe diverse issues concerning the stabilisation of geometric Kähler moduli, like blowup modes of the orbifold singularities, via D term potentials and gauge theory nonperturbative effects, like gaugino condensation. This local geometry, once embedded in a full compactification, could give rise to models with all moduli stabilised, and with the potential to lead to de Sitter vacua. Issues of gauge unification, proton stability, supersymmetry breaking