Gravitational phase transition of heavy neutrino matter

In the framework of the Thomas-Fermi model at finite temperature, we show that a cooling nondegenerate gas of massive neutrinos will undergo a phase transition in which quasi-degenerate supermassive neutrino stars are formed through gravitational collapse. For neutrinos in the mass range of 10 to 25 keV these compact dark objects could mimic the role of supermassive black holes that are usually assumed to exist at the centres galaxies. Astrophysical implications and constraints on the neutrino mass are discussed for this scenario.Comment: 10 pages, LaTex, 4 postscript figure

Spin structure of the nucleon: QCD evolution, lattice results and models

The question how the spin of the nucleon is distributed among its quark and gluon constituents is still a subject of intense investigations. Lattice QCD has progressed to provide information about spin fractions and orbital angular momentum contributions for up- and down-quarks in the proton, at a typical scale \mu^2~4 GeV^2. On the other hand, chiral quark models have traditionally been used for orientation at low momentum scales. In the comparison of such model calculations with experiment or lattice QCD, fixing the model scale and the treatment of scale evolution are essential. In this paper, we present a refined model calculation and a QCD evolution of lattice results up to next-to-next-to-leading order. We compare this approach with the Myhrer-Thomas scenario for resolving the proton spin puzzle.Comment: 11 pages, 6 figures, equation (9) has been corrected leading to a revised figure 1b. Revision matches published versio

Supermassive neutrino stars and galactic nuclei

The characteristics of supermassive 'stars' consisting of self-gravitating degenerate neutrino (or neutralino) matter are studied with particular emphasis on fermion masses around 17 keV/c2. Such compact dark objects could be as massive as 109.5 to 106.5 solar masses, with radii of about one to ten light days; they might thus mimic phenomena that are expected around the supermassive black holes recently purported at the centres of some galaxies and quasi-stellar objects.Articl

Nuclear axial polarizability and the + interaction

SIGLEAvailable from CEN Saclay, Service de Documentation, 91191 Gif-sur-Yvette Cedex (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc