No abstract available

No abstract available

[en] The first chapter is an introduction to the standard hot big bang cosmological model. The model and some of the problems associated with it are reviewed. In the second chapter, a short review of the proposals for solving the cosmological conundrums of the big-bang model is presented. The old and the new inflationary scenarios are studied, and some alternative scenarios, especially those using supersymmetry, are reviewed briefly. The third chapter is a study of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It was found that a supersymmetry breaking scale of the order of the weak breaking scale, can be obtained. In the fourth chapter, an alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied. The gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry are used

No abstract available

[en] Several aspects of inflationary cosmologies are discussed. An introduction to the standard hot big bang cosmological model is reviewed, and some of the problems associated with it are presented. A short review of the proposals for solving the cosmological conundrums of the big bang model is presented. Old and the new inflationary scenarios are discussed and shown to be unacceptable. Some alternative scenarios especially those using supersymmetry are reviewed briefly. A study is given of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It is found that a supersymmetry breaking scale of the order of the weak breaking scale. The cosmology obtained from the simplest of such models is discussed in detail and it is shown that there are no particular problems except a low reheating temperature and a violation of the thermal constraint. A possible solution to the thermal constraint problem is given by introducing a second field, and the role played by this second field in the scenario is discussed. An alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied using the gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry). This mechanism is applied to two specific models - one with and one without supersymmetry breaking. The baryon to entropy ratio is found to be dependent on parameters which are model dependent. Finally, the effect of direct coupling between the two sectors on results is related, 88 refs., 6 figs

No abstract available

[en] The nonlinear propagation of circularly polarized electromagnetic (CPEM) waves with relativistic strong amplitude in an unmagnetized cold electron-positron ion plasma is investigated. The possibility of finding soliton solutions in such a plasma is explored. In one- and two-dimensions it is shown that the presence of a small fraction of massive ions in the plasma lead to stable localized solutions. (author). 15 refs, 5 figs

[en] The effect of toroidicity during lower hybrid mode conversion is examined by treating the wave propagation in an inhomogeneous medium as an eigenvalue problem for ω²(m,n),m,n poloidal and toroidal wave numbers. Since the frequency regime near ω² = ω/sub LH/² is an accumulation point for the eigenvalue spectrum, the degenerate perturbation technique must be applied. The toroidal eigenmodes are constructed by a zeroth order superposition of monochromatic solutions with different poloidal dependence m, thus they generically exhibit a wide spectrum in k/sub parallel/ for given fixed ω² even for small inverse aspect ratio epsilon. In case that the average < k/sub parallel/> is in the neighborhood of k/sub min/, the minimum wave number for accessibility of the mode conversion regime, it is expected that excitation of toroidal modes rather than geometric optics will determine the wave coupling to the plasma

[en] The effect of the parallel equilibrium current on the linear stability of the drift-tearing mode in the collisional regime is investigated analytically. In the appropriate parameter regime, a new unstable mode, driven by equilibrium current, is found and its relevance to tokamak discharges is discussed

[en] It is demonstrated that group III atomic species in the mixed III nitrides, differing in their covalent tetrahedral radii, are not distributed at random on their sub-lattice. Two types of deviations from randomness are observed: phase separation and atomic ordering. Phase separation lowers the strain energy of the layer. The absence of phase separation in InGaN quantum wells is attributed to the stress imposed by the GaN barrier layers. Atomic ordering doubles the periodicity along the [0 0 0 1] direction