Nontrivial Geometries: Bounds on the Curvature of the Universe

Probing the geometry of the universe is one of the most important endevours in cosmology. Current observational data from the Cosmic Microwave Background anisotropy (CMB), galaxy surveys and type Ia supernovae (SNe Ia) strongly constrain the curvature of the universe to be close to zero for a universe dominated by a cosmological constant or dark energy with a constant equation of state. Here we investigate the role of cosmic priors on deriving these tight bounds on geometry, by considering a landscape motivated scenario with an oscillating curvature term. We perform a likelihood analysis of current data under such a model of non-trivial geometry and find that the uncertainties on curvature, and correspondingly on parameters of the matter and dark energy sectors, are larger. Future dark energy experiments together with CMB data from experiments like Planck could dramatically improve our ability to constrain cosmic curvature under such models enabling us to probe possible imprints of quantum gravity.Comment: 7 pages, 8 figures. Submitte

Nuclear reactions in very hot astrophysical plasmas with temperatures T > 10¹⁰ K

We use the public available TALYS code to study the spectral and temporal evolution of nuclear reactions in low-density astrophysical plasmas with ion temperatures T>1010 K. Such studies are of great interest in the context of scientific programs of future low-energy cosmic gamma-ray spectrometry. The reaction rates logarithm have been fitted as a polynomial function of temperature with seven free parameters. This makes this network convenient for calculations of reactions, especially in the case of time-dependent plasma temperature. We study the chemical abundance and gamma-ray lines emissivity evolution, and present some preliminary results for light elements such are D, T, 3He, 4He, 6Li, 7Li, 9Be, 10Be

Gamma-ray emission towards SS433/W50

Gamma-ray emission from the direction of the microquasar SS433 has been recently reported using five years of FermiLAT observations. The steady flux and a narrow spectral energy distribution peaking at 250 MeV suggest that gamma-rays could be rendered by the bulk jet kinetic power through proton-proton collisions at the SS433/W50 interaction regions. Here we report on the outcomes of the analysis of a larger Fermi-LAT data-set, using also the improved capabilities of the Pass 8 reprocessed data, which confirm and better characterize our previous results