Production spectrum of high energy electrons from high energy cosmic ray collisions

Production spectrum of high energy electrons from high energy cosmic ray collision

Inflation after Planck and BICEP2

We discuss the inflationary paradigm, how it can be tested, and how various models of inflation fare in the light of data from Planck and BICEP2. We introduce inflation and reheating, and discuss temperature and polarisation anisotropies in the cosmic microwave background radiation due to quantum fluctuations during inflation. Fitting observations of the anisotropies with theoretical realisations obtained by varying various parameters of the curvature power spectrum and cosmological parameters enables one to obtain the allowed ranges of these parameters. We discuss how to relate these parameters to inflation models which allows one to rule in or out specific models of inflation.Comment: Slightly longer version of a plenary review talk at the XXI DAE-BRNS High Energy Physics Symposium at IIT Guwahati, Dec.8-12, 2014. 14 pages, 7 fig

Pion production in high energy cosmic ray collisions

Calculations on pion energy and angle distribution in center of hydrodynamic inelastic model for nucleon-nucleon collisio

The phase-space structure of cold dark-matter halos: Insights into the Galactic halo

We study the formation of the Milky Way's halo in a $\Lambda$CDM cosmology by scaling down a high resolution simulation of the formation of a cluster of galaxies. We determine how much phase-space substructure is left over from the objects that merge to build up the present galaxy. We study the debris streams originating from such objects and find that their evolution can be explained simply in terms of the conservation of phase-space density. Analysing the mass growth history of our halo we find that its inner regions have been in place for more than 10 Gyr, but that the growth of the halo as a whole is more gradual, in agreement with other high resolution simulations of dark-matter halos. Recent accretion contributes to the inner 10 kpc of the halo only at the 10$^{-4}$ level. Finally we determine the number of dark-matter streams as a function of distance from the centre of the halo. In the equivalent of the ``Solar vicinity'', we find that the dark-matter is smoothly distributed in space, and that the velocity ellipsoid is formed by hundreds of thousands of streams, most of which have velocity dispersions of the order of 1 km/s or less.Comment: 16 pages, 21 figures, MNRAS in press. Postscript version with high resolution figures available from http://www.mpa-garching.mpg.de/~ahelmi/research/lcdm_cl.html. Minor change

Dirac phase leptogenesis

I present here a concise summary of the preprint arXiv:0707.3024, written in collaboration with A. Anisimov and P. Di Bari. There we discuss leptogenesis when {\em CP} violation stems exlusively from the Dirac phase in the PMNS mixing matrix. Under this assumption it turns out that the situation is very constrained when a hierarchical heavy right-handed (RH) neutrino spectrum is considered: the allowed regions are small and the final asymmetry depends on the initial conditions. On the other hand, for a quasi-degenerate spectrum of RH neutrinos, the {\em CP} asymmetry can be enhanced and the situation becomes much more favorable, with no dependence on the initial conditions. Interestingly, in the extreme case of resonant leptogenesis, in order to match the observed baryon asymmetry of the Universe, we obtain a lower bound on \sin \q_{13} which depends on the lightest active neutrino mass m_1.Comment: 3 pages, 2 figures, contribution to the proceedings of the TAUP 07 conference, Sep. 11-15, Sendai, Japa

The Dark UNiverse Explorer (DUNE): Proposal to ESA's Cosmic Vision

The Dark UNiverse Explorer (DUNE) is a wide-field space imager whose primary goal is the study of dark energy and dark matter with unprecedented precision. For this purpose, DUNE is optimised for the measurement of weak gravitational lensing but will also provide complementary measurements of baryonic accoustic oscillations, cluster counts and the Integrated Sachs Wolfe effect. Immediate auxiliary goals concern the evolution of galaxies, to be studied with unequalled statistical power, the detailed structure of the Milky Way and nearby galaxies, and the demographics of Earth-mass planets. DUNE is an Medium-class mission which makes use of readily available components, heritage from other missions, and synergy with ground based facilities to minimise cost and risks. The payload consists of a 1.2m telescope with a combined visible/NIR field-of-view of 1 deg^2. DUNE will carry out an all-sky survey, ranging from 550 to 1600nm, in one visible and three NIR bands which will form a unique legacy for astronomy. DUNE will yield major advances in a broad range of fields in astrophysics including fundamental cosmology, galaxy evolution, and extrasolar planet search. DUNE was recently selected by ESA as one of the mission concepts to be studied in its Cosmic Vision programme.Comment: Accepted in Experimental Astronom

Tuning the stochastic background of gravitational waves using the WMAP data

The cosmological bound of the stochastic background of gravitational waves is analyzed with the aid of the WMAP data, differently from lots of works in literature, where the old COBE data were used. From our analysis, it will result that the WMAP bounds on the energy spectrum and on the characteristic amplitude of the stochastic background of gravitational waves are greater than the COBE ones, but they are also far below frequencies of the earth-based antennas band. At the end of this letter a lower bound for the integration time of a potential detection with advanced LIGO is released and compared with the previous one arising from the old COBE data. Even if the new lower bound is minor than the previous one, it results very long, thus for a possible detection we hope in the LISA interferometer and in a further growth in the sensitivity of advanced projects.Comment: 9 pages, 2 figures, published in Modern Physics Letters A. arXiv admin note: substantial text overlap with arXiv:0901.119