C. Panagiotakopoulos

Stabilized NMSSM without domain walls

Abstract We reconsider the Next to Minimal Supersymmetric Standard Model (NMSSM) as a natural solution to the μ-problem and show that both the stability and the cosmological domain wall problems are eliminated if we impose a Z 2 R-symmetry on the non-renormalizable operators.

Higgs scalars in the minimal nonminimal supersymmetric standard model

We consider the simplest and most economic version among the proposed nonminimal supersym. models, in which the m parameter is promoted to a singlet superfield, whose self-couplings are all absent from the renormalizable superpotential. Such a particularly simple form of the renormalizable superpotential may be enforced by discrete R symmetries which are extended to the gravity-induced non-renormalizable operators as well. We show explicitly that within the supergravity-mediated supersymmetry-breaking scenario, the potentially dangerous divergent tadpoles assocd. with the presence of the gauge singlet first appear at loop levels higher than 5 and therefore do not destabilize the gauge hierarchy. The model provides a natural explanation for the origin of the m term, without suffering from the visible axion or the cosmol. domain-wall problem. Focusing on the Higgs sector of this minimal nonminimal supersym. std. model, we calc. its effective Higgs potential by integrating out the dominant quantum effects due to top squarks. We then discuss the phenomenol. implications of the Higgs scalars predicted by the theory for the present and future high-energy colliders. In particular, we find that our new minimal nonminimal supersym. model can naturally accommodate a relatively light charged Higgs boson, with a mass close to the present exptl. lower bound. [on SciFinder (R)]

New Minimal Extension of MSSM

We construct a new minimal extension of the minimal supersymmetric standard model (MSSM) by promoting the μ-parameter to a singlet superfield. The resulting renormalizable superpotential is enforced by a Z5 R-symmetry which is imposed on the non-renormalizable operators as well. The proposed model provides a natural solution to the μ-problem and is free from phenomenological and cosmological problems.

Smooth hybrid inflation.

We propose a variant of hybrid inflation which is applicable in a wide class of supersymmetric grand unified models. The observed temperature perturbations of cosmic background radiation can be reproduced with natural values of the parameters of the theory and a grand unification scale which is consistent with the unification of the minimal supersymmetric standard model gauge couplings as measured at CERN LEP. The termination of inflation is smooth and does not produce any topological defects. Finally, we present a specific supersymmetric model where our smooth hybrid inflationary scenario is realized.

Supersymmetric unification without proton decay

Abstract We present a supersymmetric grand unification scheme based on the gauge group SU(3) c × SU(3) L × SU(3) R in which the proton and the lightest supersymmetric particle are stable, neutrinos are necessarily massive, and the observed baryon asymmetry originates in the lepton sector. Such models are also consistent with the measured value of sin 2 θ W as well as unification of the gauge couplings.We present a supersymmetric grand unification scheme based on the gauge group SU(3)_c X SU(3)_L X SU(3)_R in which the proton and the lightest supersymmetric particle are stable, neutrinos are necessarily massive, and the observed baryon asymmetry originates in the lepton sector. Such models are also consistent with the measured value of sin^2\Theta_W as well as unification of the gauge couplings.

Relaxing the cosmological bound on axions

Abstract The usual cosmological bound on axions states that the axion decay constant ƒ a ≲ 10 12 GeV in order that the energy density in axions today is not unacceptably large. It is shown that this bound on ƒ a can be substantially relaxed in a class of superstring models with a superheavy intermediate scale. Implications for the model-independent axion of superstring theories are indicated.

Blue perturbation spectra from hybrid inflation with canonical supergravity

We construct a hybrid inflationary model associated with the superheavy scale M{sub X}{approximately}10{sup 16} GeV of supersymmetric grand unified theories in which the inflaton potential is provided entirely by canonical supergravity. We find that the spectrum of adiabatic density perturbations is characterized by a strongly varying spectral index which is considerably larger than unity. Moreover, the total number of e-foldings is very limited. Implications of our analysis for other hybrid inflationary scenarios are briefly discussed. {copyright} {ital 1997} {ital The American Physical Society}

MSSM from SUSY trinification

We construct a SU (3)3 supersymmetric gauge theory with a common gauge coupling g using only fields belonging to 27, 27 and singlet representations of E6. Spontaneous breaking of this gauge group at a scale Mx=1.3×1016GeV gives naturally rise exactly to the minimal supersymmetric standard model (MSSM) and, consequently, to the experimentally favored values of sin2θW and αs. The gauge hierarchy problem is naturally solved by a missing-partner-type mechanism which works to all orders in the superpotential. The baryon asymmetry can be generated in spite of the (essential) stability of the proton. The solar neutrino puzzle is solved by the MSW mechanism. The LSP is a natural “cold” dark matter candidate and “hot” dark matter might consist of τ-neutrinos. This model could be thought of as an effective 4D theory emerging from a more fundamental theory at a scale Mc=Mp/8π where aG≡g2/4π happens to be equal to unity.

Topology of 2D lattice gauge fields

Abstract A local topological charge density for two-dimensional (2d) U(1) lattice gauge field is defined. A Monte Carlo (MC) simulation of pure 2d U(1) lattice gauge theory is carried out and results are obtained for the topological susceptibility and the mean value of the topological charge density in units of the string tension in a θ vacuum. The dilute gas approximation appears to be very successful. Definitions of the topological charge not based on a local charge density, analogous to the ones used in MC studies of four-dimensional lattice gauge theories, are also considered and detailed comparisons are made. These non-local charges are found to have several undesirable features.

Hybrid inflation with quasi-canonical supergravity☆

Abstract We construct a hybrid inflationary model associated with the superheavy scale M x ⋍ 2 × 10 16 GeV of the minimal supersymmetric standard model which is based on the simplest superpotential for symmetry breaking and in which the inflaton potential along the inflationary trajectory is essentially provided by quasi-canonical supergravity. The resulting spectrum of adiabatic density perturbations is blue and the duration of inflation sufficient but rather limited.