6,965 research outputs found

### Cosmological constraints on Neutrino - Dark Matter interactions

I summarize the results of a recent analysis where the cosmological effects
of interactions of neutrinos with cold Dark Matter (DM) is investigated. This
interaction produces diffusion-damped oscillations in the matter power
spectrum, analogous to the acoustic oscillations in the baryon-photon fluid. I
discuss the bounds from the Sloan Digital Sky Survey on the corresponding
opacity defined as the ratio of neutrino-DM scattering cross section over DM
mass, and compare with the constraint from observation of neutrinos from
supernova 1987A.Comment: Talk given at the Neutrino Oscillation Workshop NOW2006, Otranto,
Italy, September 9-16 200

### Inflationary Cosmology from Noncommutative Geometry

In the framework of the Connes-Lott model based on noncommutative geometry,
the basic features of a gauge theory in the presence of gravity are reviewed,
in order to show the possible physical relevance of this scheme for
inflationary cosmology. These models naturally contain at least two scalar
fields, interacting with each other whenever more than one fermion generation
is assumed. In this paper we propose to investigate the behaviour of these two
fields (one of which represents the distance between the copies of a
two-sheeted space-time) in the early stages of the universe evolution. In
particular the simplest abelian model, which preserves the main characteristics
of more complicate gauge theories, is considered and the corresponding
inflationary dynamics is studied. We find that a chaotic inflation is naturally
favoured, leading to a field configuration in which no symmetry breaking occurs
and the final distance between the two sheets of space-time is smaller the
greater the number of $e$-fold in each sheet.Comment: 29 pages, plain Latex, + 2 figures as uuencoded postscript files,
substantially revised version to appear in the Int. Jour. Mod. Phys.

### Constraints on Unified Gauge Theories from Noncommutative Geometry

The Connes and Lott reformulation of the strong and electroweak model
represents a promising application of noncommutative geometry. In this scheme
the Higgs field naturally appears in the theory as a particular `gauge boson',
connected to the discrete internal space, and its quartic potential, fixed by
the model, is not vanishing only when more than one fermion generation is
present. Moreover, the exact hypercharge assignments and relations among the
masses of particles have been obtained. This paper analyzes the possibility of
extensions of this model to larger unified gauge groups. Noncommutative
geometry imposes very stringent constraints on the possible theories, and
remarkably, the analysis seems to suggest that no larger gauge groups are
compatible with the noncommutative structure, unless one enlarges the fermionic
degrees of freedom, namely the number of particles.Comment: 18 pages, Plain LaTeX, no figure

### Primordial Nucleosynthesis, Cosmic Microwave Background and Neutrinos

We report the results of a recent likelihood analysis combining the
primordial nucleosynthesis and the BOOMERanG and MAXIMA-1 data on cosmic
microwave background radiation anisotropies. We discuss the possible
implications for relic neutrino background of a high value for the baryonic
matter content of the universe, larger than what is expected in a standard
nucleosynthesis scenario.Comment: 3 pages, 1 figure, some typos corrected, one reference added,
presented by G. Mangano at NOW 2000, Europhysics Neutrino Oscillation
Workshop, Otranto 200

### Three Flavour Majorana Neutrinos with Magnetic Moments in a Supernova

The resonant transition effects MSW and NSFP for three flavour Majorana
neutrinos in a supernova are considered, where the transition magnetic moments
are likely to play a relevant role in neutrino physics. In this scenario, the
deformed thermal neutrino distributions are obtained for different choices of
the electron-tau mixing angle. Detailed predictions for the future large
neutrino detectors are also given in terms of the ratio between the spectra of
recoil electrons for deformed and undeformed spectra.Comment: 20 pages, LaTeX, 5 figures.p

### Neutrino masses and baryogenesis in SO(10) unified theories

We report on some phenomenological implications of a class of unified models
based on SO(10) gauge group, with intermediate symmetry group containing
SU(2)_R. Interesting predictions for neutrino masses are discussed, which are
relevant both for solar neutrino and dark matter problems, as well as a model
for the formation of the baryon asymmetry of the universe required by
primordial nucleosynthesis.Comment: Latex 16 pages, 1 ps figure. Appeared in Proceedings of seventh
International Workshop on Neutrino Telescopes, Venezia February 27 - March 1
1996, Editor M. Baldo Ceoli

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