Warm inflation model building

We review the main aspects of the warm inflation scenario, focusing on the inflationary dynamics and the predictions related to the primordial spectrum of perturbations, to be compared with the recent cosmological observations. We study in detail three different classes of inflationary models, chaotic, hybrid models and hilltop models, and discuss their embedding into supersymmetric models and the consequences for model building of the warm inflationary dynamics based on first principles calculations. Due to the extra friction term introduced in the inflaton background evolution generated by the dissipative dynamics, inflation can take place generically for smaller values of the field, and larger values of couplings and masses. When the dissipative dynamics dominates over the expansion, in the so-called strong dissipative regime, inflation proceeds with sub-planckian inflaton values. Models can be naturally embedded into a supergravity framework, with sugra corrections suppressed by the Planck mass now under control, for a larger class of K\"ahler potentials. In particular, this provides a simpler solution to the "eta" problem in supersymmetric hybrid inflation, without restricting the K\"ahler potentials compatible with inflation. For chaotic models dissipation leads to a smaller prediction for the tensor-to-scalar ratio and a less tilted spectrum when compared to the cold inflation scenario. We find in particular that a small component of dissipation renders the quartic model now consistent with the current CMB data.Comment: 22 pages, 5 figure

Primordial Black Holes: sirens of the early Universe

Primordial Black Holes (PBHs) are, typically light, black holes which can form in the early Universe. There are a number of formation mechanisms, including the collapse of large density perturbations, cosmic string loops and bubble collisions. The number of PBHs formed is tightly constrained by the consequences of their evaporation and their lensing and dynamical effects. Therefore PBHs are a powerful probe of the physics of the early Universe, in particular models of inflation. They are also a potential cold dark matter candidate.Comment: 21 pages. To be published in "Quantum Aspects of Black Holes", ed. X. Calmet (Springer, 2014

Kinetics of the initial stages of film formation during low pressure chemical vapour deposition of polysilicon by pyrolysis of silane

A kinetic model for description of the process of silicon film formation on silica by thermal decomposition of silane at reduced pressure has been proposed. The model is based on the concept of kinetic interdependence between heterogeneous catalytic chemical reaction and fundamental structure forming phenomena - nucleation and nuclei growth. A number of experimental data for deposition rates and polysilicon grains sizes have been mathematically processed in order to derive kinetic equations for the rates of nucleation and nuclei growth as functions of reactor operating conditions (pressure and temperature) as well as process duration. Furthermore, based on both the good correspondence achieved between the experimental results and the model, and the deductions of thermodynamic theory of nucleation, the kinetic equations derived were analysed in regard to the general description of silicon film structure evolution. The analysis of the model, by confïrming the general trends established between the arrival and the surface diffusion rates of silicon adspecies, contributes to clarify the mechanism of the initial stages of film microstructure formation. The results obtained show that kinetics of structure evolution can be successfully described by developing the existing CVD phenomenological kinetic models further to an atomistic level

Frontières

La réalité des frontières semble s’être inversée : alors que les Etats contrôlaient leurs frontières en les fermant de l’intérieur, le droit de sortie s’est généralisé mais le droit d’entrer ailleurs est devenu de plus en difficile pour les deux tiers de la population de la planète. Ces frontières sont multiples, ayant chacune leur logique, leur efficacité et leur périmètres : imaginaires, imaginées et mises en œuvre avec la chute du " rideau de fer ", dans le cadre de l’Europe de Schengen, contrôlée par Frontex, documentée par Eurodac. La logique des murs, des camps, des centres de rétention et des zones d’attente, concrétise la manière dont l’Autre est appréhendé dans les représentations et au quotidien. Ce dossier va explorer dans une vision géopolitique la plus large possible ces frontières emblématiques pour en analyser les modes opératoires et les conséquences sur les territoires et les populations concernées, en revisitant la souveraineté nationale, les politiques publiques et les relations internationales. The reality of the borders seems to have been reversed: while States checked their borders by closing them from the inside, the right of exit became widespread but the right to enter somewhere else became harder and harder for two thirds of the population of the planet. These borders are multiple, having each their logic, their efficiency and them perimeters: imaginary, imagined and implemented with the fall of the "Iron Curtain", within the framework of Europe of Schengen, checked by Frontex, informed by Eurodac. The logic of walls, camps, detention centers and waiting areas, concretizes the way the Other one is dreaded in the representations and in everyday life