Sparticle spectrum of large volume compactification

Recent observations constrain the amount of Dark Radiation (∆N eff ) and may even hint towards a non-zero value of ∆N eff . It is by now well-known that this puts stringent constraints on the sequestered Large Volume Scenario (LVS), i.e. on LVS realisations with the Standard Model at a singularity. We go beyond this setting by considering LVS models where SM fields are realised on 7-branes in the geometric regime. As we argue, this naturally goes together with high-scale supersymmetry. The abundance of Dark Radiation is determined by the competition between the decay of the lightest modulus to axions, to the SM Higgs and to gauge fields, and leads to strict constraints on these models. Nevertheless, these constructions can in principle meet current DR bounds due to decays into gauge bosons alone. Further, a rather robust prediction for a substantial amount of Dark Radiation can be made. This applies both to cases where the SM 4-cycles are stabilised by D-terms and are small 'by accident', i.e. tuning, as well as to fibred models with the small cycles stabilised by loops. In these constructions the DR axion and the QCD axion are the same field and we require a tuning of the initial misalignment to avoid Dark Matter overproduction. Furthermore, we analyse a closely related setting where the SM lives at a singularity but couples to the volume modulus through flavour branes. We conclude that some of the most natural LVS settings with natural values of model parameters lead to Dark Radiation predictions just below the present observational limits. Barring a discovery, rather modest improvements of present Dark Radiation bounds can rule out many of these most simple and generic variants of the LVS.

Section: Jhep09(2014)140mentioning

confidence: 99%

Dark Radiation predictions from general Large Volume Scenarios

Hebecker

Mangat

Rompineve

et al. 2014

“…The two kinds of corrections are: mixings amongst the moduli that are induced by loop contributions to gauge kinetic terms, as described in ref. [73,74]; and corrections due to loops of heavy particles on the supersymmetry-breaking SM brane, as described in ref. [54][55][56].…”

Section: Modulus Spectrum and Couplings: Correctionsmentioning

confidence: 99%

“…Although this is not a significant change for branes that are already in the geometric regime, having τ ′ 4 nonzero can (but need not) significantly change the predictions for branes localised at singularities. Detailed studies [73,74] show that this kind of correction really does arise for combinations of D3s/D7s located at orbifold singularities JHEP10(2011)119 Table 6. Modulus couplings to brane gauge bosons for the small-hierarchy singular regime, including the 1-loop modulus redefinition.…”

Section: Modulus Spectrum and Couplings: Correctionsmentioning

confidence: 99%

Anisotropic modulus stabilisation: strings at LHC scales with micron-sized extra dimensions

Cicoli

Burgess

Quevedo

2011

151

We construct flux-stabilised Type IIB string compactifications whose extra dimensions have very different sizes, and use these to describe several types of vacua with a TeV string scale. Because we can access regimes where two dimensions are hierarchically larger than the other four, we find examples where two dimensions are micron-sized while the other four are at the weak scale in addition to more standard examples with all six extra dimensions equally large. Besides providing ultraviolet completeness, the phenomenology of these models is richer than vanilla large-dimensional models in several generic ways: (i) they are supersymmetric, with supersymmetry broken at sub-eV scales in the bulk but only nonlinearly realised in the Standard Model sector, leading to no MSSM superpartners for ordinary particles and many more bulk missing-energy channels, as in supersymmetric large extra dimensions (SLED); (ii) small cycles in the more complicated extra-dimensional geometry allow some KK states to reside at TeV scales even if all six extra dimensions are nominally much larger; (iii) a rich spectrum of string and KK states at TeV scales; and (iv) an equally rich spectrum of very light moduli exist having unusually small (but technically natural) masses, with potentially interesting implications for cosmology and astrophysics that nonetheless evade new-force constraints. The hierarchy problem is solved in these models because the extra-dimensional volume is naturally stabilised at exponentially large values: the extra dimensions are Calabi-Yau geometries with a 4D K3 or T 4 -fibration over a Open Access doi:10.1007/JHEP10 (2011)119 JHEP10 (2011)119 2D base, with moduli stabilised within the well-established LARGE-Volume scenario. The new technical step is the use of poly-instanton corrections to the superpotential (which, unlike for simpler models, are likely to be present on K3 or T 4 -fibered Calabi-Yau compactifications) to obtain a large hierarchy between the sizes of different dimensions. For several scenarios we identify the low-energy spectrum and briefly discuss some of their astrophysical, cosmological and phenomenological implications.

“…In fact as shown in [24], when the standard model is on a D3 brane, the µ term is proportional to imaginary anti-self dual (IASD) fluxes, i.e. fluxes which break SUSY in the dilaton and/or the complex structure moduli directions 6 . But these are zero at the LVS minimum.…”

Section: Non-perturbative Terms In the Superpotential And Fcncmentioning

confidence: 97%

“…The last possibility, leading to soft masses at the gravitino scale [6], arises if there is moduli mixing as suggested in [7]. However the argument for this relies on pushing the field theory formalism beyond the string scale.…”

Section: Introductionmentioning

confidence: 99%

Constraints on LVS compactifications of IIB string theory

Alwis

2012

We argue that once all theoretical and phenomenological constraints are imposed on the different versions of the Large Volume Scenario (LVS) compactifications of type IIB string theory, one particular version is favored. This is essentially a sequestered one in which the soft terms are generated by Weyl anomaly and RG running effects. We also show that arguments questioning sequestering in LVS models are not relevant in this case. † dealwiss@colorado.edu 1