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Last and nearest GRB-XRF 080109 has been an exceptional lesson on GRB nature. After a decade (since 25 April 08) we know that Supernovae may often contain a Jet. Its persistent activity may shine on axis as a GRBs. Such a persistent, thin beamed gamma jet may be powered by either a BH (Black Holes) or Pulsars. Late stages of these jets may loose the SN traces and appear as a short GRB or a long orphan GRB (depending on jet angular velocity and view angle). XRF are peripherical viewing of the jets. These precessing and spinning gamma jet are originated by Inverse Compton and-or Synchrotron Radiation at pulsars or micro-quasars sources, by ultra-relativistic electrons. These Jets are most powerful at Supernova birth, blazing, once on axis, to us and flashing GRB detector. The trembling of the thin jet explains naturally the observed erratic multi-explosive structure of different GRBs. The jets are precessing (by binary companion or inner disk asymmetry) and decaying by power on time scales of few hours, but they keep staying inside the observer cone view only a few seconds duration times (GRB); the jet is thinner in gamma and wider in X band. This explain the wider and longer X GRB afterglow duration and the rare presence of X-ray precursors., Comment: 11 pages, 12 figures

Considering heavy stable neutrinos of 4th generation we calculate the relic density of such neutrinos in the Universe. Taking into account the condensation of heavy neutrinos in the Galaxy and applying the results of calculations to experimental data from underground experiments on search for WIMPs in elastic neutral current scattering on nuclei we found an exclusion region of neutrino mass 60 GeV < m < 290 GeV. The bounds obtained from present underground experiments while confirming the previous bounds derived from analysis of cosmic ray spectra are more relible ones. We discuss also the first indication of elastic scattering induced by WIMP in DAMA experiment finding a very narrow window of neutrino mass 45 GeV < m < 50 GeV compatible with the possible signal rate in the detector., 12 pages, 3 figures

A fourth generation of fermions predicted by the phenomenological heterotic string models can possess a new, strictly conserved charge. Among other things, this leads to the hypothesis of the existence of a fourth massive stable neutrino. A comparison of this hypothesis with the data obtained in the DAMA underground experiment to search for massive weakly-interacting cosmic particles with hidden mass and with the EGRET measurements of the >1 GeV galactic gamma-ray background gives a value m approximate to 50 GeV for the possible mass of the fourth neutrino. It is shown that the hypothesis can be checked in accelerator experiments. The positron signal from annihilation of massive relic neutrinos in the galaxy is calculated. A search for this signal is is within the reach of planned cosmic-ray investigations. (C) 1999 American Institute of Physics. [S0021-3640(99)00206-6].

We discuss the possibility of searching for very heavy neutrinos of new generations in accelerator experiments (by the process {ital e}{sup +}{ital e}{sup {minus}}{r_arrow}{nu}{bar {nu}}{gamma}), which allow investigation in the region {ital m}{sub {nu}}{approximately}{ital M}{sub {ital Z}}/2, where it is difficult to get cosmological constraints on the neutrino mass. {copyright} {ital 1996 The American Physical Society.}

We consider the possibility of detecting in a hypothetical 1 km3 neutrino telescope high energy neutrinos resulting from the annihilation of very heavy neutrinos of fourth generation in the galactic halo. It is shown that such a large telescope could in principle detect this negligible component which, if it does exist, gives a contribution of order 10–2 to the dark matter of the universe.

Considering the annihilation of massive tau-neutrinos in the Galactic Halo, we show that it is difficult to obtain concordance between the observed (directly on indirectly) and predicted fluxes of cosmic electrons and positrons in the case of a stable tau-neutrino with mass approximate to 1-24 MeV and magnetic moment mu similar to 10(-6) mu(B). These results exclude the possibility Tor such a tau-neutrino being the dominant cold dark matter particle component.

Taking into account neutrino condensation in the gravitational field of collapsing matter, we investigate the annihilation of heavy relic neutrinos in the Galaxy resulting in the generation of cosmic rays. The main neutrino annihilation processes are considered: i.e., nu --> f (f) over bar and nu --> W+W-. The condensation mechanism allows one to get information on the density distribution in the Galaxy halo without any recourse in an explicit dynamical halo model, and the resulting cosmic ray spectrum provides constraints on the heavy neutrino mass. The comparison of the predicted cosmic ray flux with the observed one excludes the heavy neutrino mass range 60 GeV < m(nu) < 115 GeV. Such a restriction leads to a bound on the present energy density of very heavy neutrinos which may be comparable to the corresponding baryonic one only in the range 115 GeV < m(nu) < 300 GeV. Our approach is valid for multicomponent dark matter and can be used for species that give even a negligible contribution to the critical cosmological density.