Dark Neutrinos

Solar, atmospheric and reactor neutrino experiments established that neutrinos are massive. It is quite natural then to consider neutrinos as candidate particles for explaining the dark matter in halos around galaxies. We study the gravitational clustering of these neutrinos within a model of a massive core and a surrounding spherical neutrino halo. The neutrinos form a degenerate Fermi gas and a loaded polytropic equation is established. We solve the equation and we obtain the neutrino density in a galaxy, the size of the galaxy and the galactic rotational curves. The available data favor a neutrino with a mass around 10eV. The consequent cosmological implications are examined.Comment: 5 pages, 2 figure

Neutrino Shortcuts in Spacetime

Theories with large extra dimensions may be tested using sterile neutrinos living in the bulk. A bulk neutrino can mix with a flavor neutrino localized in the brane leading to unconventional patterns of neutrino oscillations. A resonance phenomenon, strong mixing between the flavor and the sterile neutrino, allows to determine the radius of the large extra dimension. If our brane is curved, then the sterile neutrino can take a shortcut through the bulk, leading to an apparent superluminal neutrino speed. The amount of "superluminality" is directly connected to parameters determining the shape of the brane. On the experimental side, we suggest that a long baseline neutrino beam from CERN to NESTOR neutrino telescope will help to clarify these important issues.Comment: To appear in Mod. Phys. Lett. A 201

TeV Neutrinos in a dense medium

The dispersion relation of energetic (few TeV) neutrinos traversing a medium is studied. We use the real time formalism of thermal field theory and we include the effects from the propagator of the W gauge boson. We consider then the MSW oscillations for cosmic neutrinos traversing the Earth, adopting for the neutrino parameters values suggested by the LSND results. It is found that the $\nu_\mu$ flux, for neutrinos passing through the center of the Earth, will appear reduced by 15% for energies around 10 TeV.Comment: 12 pages, latex, 2 figure

Relational Quantum Mechanics

We suggest that the inner syntax of Quantum Mechanics is relational logic, a form of logic developed by C. S. Peirce during the years 1870 - 1880. The Peircean logic has the structure of category theory, with relation serving as an arrow (or morphism). At the core of the relational logical system is the law of composition of relations. This law leads to the fundamental quantum rule of probability as the square of an amplitude. Our study of a simple discrete model, extended to the continuum, indicates that a finite number of degrees of freedom can live in phase space. This "granularity" of phase space is determined by Planck's constant h. We indicate also the broader philosophical ramifications of a relational quantum mechanics.Comment: arXiv admin note: text overlap with arXiv:0804.3080, arXiv:0812.194

String Quantization in Curved Spacetimes: Null String Approach

We study quantum strings in strong gravitational fields. The relevant small parameter is $g=R_c{\sqrt T_0}$, where $R_c$ is the curvature of the spacetime and $T_0$ is the string tension. Within our systematic expansion we obtain to zeroth order the null string (string with zero tension), while the first order correction incorporates the string dynamics. We apply our formalism to quantum null strings in de Sitter spacetime. After a reparametrization of the world-sheet coordinates, the equations of motion are simplified. The quantum algebra generated by the constraints is considered, ordering the momentum operators to the right of the coordinate operators. No critical dimension appears. It is anticipated however that the conformal anomaly will appear when the first order corrections proportional to $T_0$, are introduced.Comment: 6 pages, plain Tex, no figure