Cosmological models consistent with supersymmetric compactiflcation of superstring theories

The compactification of 10-dimensional supergravity, coupled to super Yang-Mills theory, to curved 4-dimensional spacetimes is investigated. The requirement of unbroken supersymmetry leads to a set of consistency conditions. These are fairly restrictive, but nevertheless permit some nontrivial solutions, including the Milne universe. More general time-dependent metrics are also not ruled out.     

Higgs phenomenology of the supersymmetric model with a gauge singlet

We discuss the Higgs sector of the supersymmetric standard model extended by a gauge singlet for the range of parameters, which is compatible with universal soft supersymmetry breaking terms at the GUT scale. We present results for the masses, couplings and decay properties of the lightest Higgs bosons, in particular with regard to Higgs boson searches at LEP. The prospects differ significantly from the ones within the MSSM.     

Non-Linear realization of supersymmetry algebra from supersymmetric constraint

We discuss spontaneous symmetry breaking of global supersymmetry for a single scalar superfield in an arbitrary Kähler manifold. We show that when the curvature of the manifold goes to infinity (or, equivalently, the masses of the scalar partners of the goldstino go to infinity) a non-linear realization of supersymmetry is obtained. The model can be described, in perfect analogy to the ordinary σ-models, by means of a supersymmetric constraint on the superfield Φ, of the form Φ²=0. The non-linear realization we obtain is different from that of Volkov and Akulov. The differences among the two realizations are discussed.     

Erratum to: Analysis of the neutralino system in supersymmetric theories

The European Physical Journal C - In the preceding reference [1] we have shown how the fundamental gaugino and higgsino parameters of the chargino and neutralino system in supersymmetric theories...     

Cosmological and astrophysical bounds on the scale of supersymmetry breaking

We derive an upper bound f < 10⁶ GeV on the scale of the breaking of supersymmetry from the mass density of the universe and a lower bound f 40 GeV from stellar evolution.     

Solving the little hierarchy problem with a light singlet and supersymmetric mass terms

A generalization of the Next-to-Minimal Supersymmetric Model (NMSSM) is studied in which an explicit μ-term as well as a small supersymmetric mass term for the singlet superfield are incorporated. We study the possibility of raising the Standard Model-like Higgs mass at tree level through its mixing with a light, mostly-singlet, CP-even scalar. We are able to generate Higgs boson masses up to 145 GeV with top squarks below 1.1 TeV and without the need to fine tune parameters in the scalar potential. This model yields light singlet-like scalars and pseudoscalars passing all collider constraints.     

Spontaneous breaking of scale invariance in a supersymmetric model

The phase structure of a large N, O(N) supersymmetric model in three dimensions is studied. Of special interest is the spontaneous breaking of scale invariance which occurs at a fixed value of the coupling constant, λ₀=λ_c=4π. In this phase the bosons and fermions acquire a mass while a Goldstone boson (dilaton) and Goldstone fermion (“dilatino”) are dynamically generated as massless bound states. The absence of renormalization of the dimensionless coupling constant λ₀ leaves these Goldstone particles massless.     

Influence of the minimal supersymmetric standard model extended by an additional Higgs singlet on the anomalous magnetic moment of the muon

We present the results of the influence of the minimal supersymmetric standard model with an additional Higgs singletN, with vacuum expectation valuev _N, on the anomalous magnetic moment of the muon. This gives different mass matrices for the charginos and neutralinos, which are taken into account within the relevant penguin diagrams leading to a contribution Δa _μ to the anomalous magnetic moment of the muon. We show that a large vacuum expectation value for the Higgs singlet leads to a suppression of the supersymmetric contribution making it difficult to see in an experiment in the near future.     

Global lepton-quark neutral current constraint on low scale gravity model

We perform a global analysis of the lepton-quark neutral current data on the low scale gravity model, which arises from the extra dimensions. The global data include HERA neutral current deep-inelastic scattering, Drell-Yan production at the Tevatron, and fermion pair production at LEPII. The Drell-Yan production, due to the large invariant mass data, provides the strongest constraint. Combining all data, the effective Planck scale must be larger than about 1.12 TeV for n=3 and 0.94 TeV for n=4 at 95%CL.     

Cosmological Constant and Stability of the Cosmological Models

The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters λ and k were discussed respectively. Near λ = 0, the cosmological model is unstable with the change of λ, and near λ = β = 0, the cosmological model is unstable with the change of k. So when we consider the stable cosmological model, we must consider the nonzero cosmological constant.