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665
Quantization of Fourform Fluxes and Dynamical Neutralization Of The Cosmological Constant
, 2000
"... A fourform gauge flux makes a variable contribution to the cosmological constant. This has often been assumed to take continuous values, but we argue that it has a generalized Dirac quantization condition. For a single flux the steps are much larger than the observational limit, but we show that wi ..."
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Cited by 274 (21 self)
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A fourform gauge flux makes a variable contribution to the cosmological constant. This has often been assumed to take continuous values, but we argue that it has a generalized Dirac quantization condition. For a single flux the steps are much larger than the observational limit, but we show that with multiple fluxes the allowed values can form a sufficiently dense ‘discretuum’. Multiple fluxes generally arise in M theory compactifications on manifolds with nontrivial threecycles. In theories with large extra dimensions a few fourforms suffice; otherwise of order 100 are needed. Starting from generic initial conditions, the repeated nucleation of membranes dynamically generates regions with λ in the observational range. Entropy and density perturbations can be produced.
The Confrontation between General Relativity and Experiment
 Living Rev. Relativity 9
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The dS/CFT correspondence
 JHEP
, 2001
"... A holographic duality is proposed relating quantum gravity on dSD (Ddimensional de Sitter space) to conformal field theory on a single SD−1 ((D1)sphere), in which bulk de Sitter correlators with points on the boundary are related to CFT correlators on the sphere, and points on I + (the future bou ..."
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Cited by 196 (7 self)
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A holographic duality is proposed relating quantum gravity on dSD (Ddimensional de Sitter space) to conformal field theory on a single SD−1 ((D1)sphere), in which bulk de Sitter correlators with points on the boundary are related to CFT correlators on the sphere, and points on I + (the future boundary of dSD) are mapped to the antipodal points on SD−1 relative to those on I −. For the case of dS3, which is analyzed in some detail, the central charge of the CFT2 is computed in an analysis of the asymptotic symmetry group at I ±. This dS/CFT proposal is supported by the computation of correlation functions of a massive scalar field. In general the dual CFT may be nonunitary and (if for example there are sufficently massive stable scalars) contain complex conformal weights. We also consider the physical region O − of dS3 corresponding to the causal past of a timelike observer, whose holographic dual lives on a plane rather than a sphere. O − can be foliated by asymptotically flat spacelike slices. Time evolution along these slices is generated by
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
Orientifolds of K3 and CalabiYau manifolds with intersecting Dbranes
 JHEP
"... We investigate orientifolds of type II string theory on K3 and CalabiYau 3folds with intersecting Dbranes wrapping special Lagrangian cycles. We determine quite generically the chiral massless spectrum in terms of topological invariants and discuss both orbifold examples and algebraic realization ..."
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Cited by 85 (16 self)
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We investigate orientifolds of type II string theory on K3 and CalabiYau 3folds with intersecting Dbranes wrapping special Lagrangian cycles. We determine quite generically the chiral massless spectrum in terms of topological invariants and discuss both orbifold examples and algebraic realizations in detail. Intriguingly, the developed techniques provide an elegant way to figure out the chiral sector of orientifold models without computing any explicit string partition function. As a new example we derive a nonsupersymmetric Standardlike Model from an orientifold of type IIA on the quintic CalabiYau 3fold with wrapped D6branes. In the case of supersymmetric intersecting brane models on CalabiYau manifolds we discuss the Dterm and Fterm potentials, the effective gauge couplings and the GreenSchwarz mechanism. The mirror symmetric formulation of this construction is provided within type IIB theory. We finally include a short discussion about the lift of these models from type IIB on K3 to Ftheory and from type IIA on CalabiYau 3folds to Mtheory on G2 manifolds. 06/2002
Strong dynamics and electroweak symmetry breaking
, 2002
"... The breaking of electroweak √ symmetry, and origin of the associated “weak scale, ” vweak = 1 / 2 √ 2GF = 175 GeV, may be due to a new strong interaction. Theoretical developments over the past decade have led to viable models and mechanisms that are consistent with current experimental data. Many o ..."
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Cited by 81 (0 self)
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The breaking of electroweak √ symmetry, and origin of the associated “weak scale, ” vweak = 1 / 2 √ 2GF = 175 GeV, may be due to a new strong interaction. Theoretical developments over the past decade have led to viable models and mechanisms that are consistent with current experimental data. Many of these schemes feature a priveleged role for the top quark, and third generation, and are natural in the context of theories of extra space dimensions at the weak scale. We review various models and their phenomenological implications which will be subject to definitive tests in future collider runs at the Tevatron, and the LHC, and future linear e + e − colliders, as well as sensitive
Yukawa couplings in intersecting Dbrane models
 JHEP
"... Abstract: We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kähler and open string mod ..."
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Cited by 76 (9 self)
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Abstract: We compute the Yukawa couplings among chiral fields in toroidal Type II compactifications with wrapping D6branes intersecting at angles. Those models can yield realistic standard model spectrum living at the intersections. The Yukawa couplings depend both on the Kähler and open string moduli but not on the complex structure. They arise from worldsheet instanton corrections and are found to be given by products of complex Jacobi theta functions with characteristics. The Yukawa couplings for a particular intersecting brane configuration yielding the chiral spectrum of the MSSM are computed as an example. We also show how our methods can be extended to compute Yukawa couplings on certain classes of elliptically fibered CY manifolds which are mirror to complex cones over del Pezzo surfaces. We find that the Yukawa couplings in intersecting D6brane models have a mathematical interpretation in the context of homological mirror symmetry. In particular, the computation of such Yukawa couplings is related to the construction of
Out of this world supersymmetry breaking
 Nucl. Phys. B
, 1999
"... We show that in a general hidden sector model, supersymmetry breaking necessarily generates at oneloop a scalar and gaugino mass as a consequence of the superWeyl anomaly. We study a scenario in which this contribution dominates. We consider the Standard Model particles to be localized on a (3+1) ..."
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Cited by 68 (1 self)
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We show that in a general hidden sector model, supersymmetry breaking necessarily generates at oneloop a scalar and gaugino mass as a consequence of the superWeyl anomaly. We study a scenario in which this contribution dominates. We consider the Standard Model particles to be localized on a (3+1)dimensional subspace or “3brane ” of a higher dimensional spacetime, while supersymmetry breaking occurs off the 3brane, either in the bulk or on another 3brane. At least one extra dimension is assumed to be compactified roughly one to two orders of magnitude below the fourdimensional Planck scale. This framework is phenomenologically very attractive; it introduces new possibilities for solving the supersymmetric flavor problem, the gaugino mass problem, the supersymmetric CP problem, and the µproblem. Furthermore, the compactification scale can be consistent with a unification of gauge and gravitational couplings. We demonstrate these claims in a fourdimensional effective theory below the compactification scale that incorporates the relevant features of the underlying higher dimensional theory and the contribution of the superWeyl anomaly. Naturalness constraints follow not only from symmetries but also from the higher dimensional
Standard models from heterotic Mtheory
, 2000
"... We present a class of N = 1 supersymmetric models of particle physics, derived directly from heterotic Mtheory, that contain three families of chiral quarks and leptons coupled to the gauge group SU(3)C×SU(2)L×U(1)Y. These models are a fundamental form of “braneworld” theories, with an observable ..."
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Cited by 55 (17 self)
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We present a class of N = 1 supersymmetric models of particle physics, derived directly from heterotic Mtheory, that contain three families of chiral quarks and leptons coupled to the gauge group SU(3)C×SU(2)L×U(1)Y. These models are a fundamental form of “braneworld” theories, with an observable and hidden sector each confined, after compactification on a Calabi–Yau threefold, to a BPS threebrane separated by a fivedimensional bulk space with size of the order of the intermediate scale. The requirement of three families, coupled to the fundamental conditions of anomaly freedom and supersymmetry, constrains these models to contain additional fivebranes wrapped around holomorphic curves in the Calabi–Yau threefold. These fivebranes “live” in the bulk space and represent new, nonperturbative aspects of these particle physics vacua. We discuss, in detail, the relevant mathematical structure of a class of torusfibered Calabi–Yau threefolds with nontrivial first homotopy groups and construct holomorphic vector bundles over such threefolds, which, by including Wilson lines, break the gauge symmetry to the standard model gauge group. Rules for constructing phenomenological particle physics models in this context are presented and we give a number of explicit examples.
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.