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Research Interests
  • Cosmology: Dark Matter, Dark Energy, Tests of General Relativity and
    the standard cosmological model.
  • High Energy Astrophysics: A Unified Theory of High Energy Astrophysical
    Phenomena (Gamma Ray Bursts, Cosmic Rays, Cosmic Gamma
    Rays and Neutrinos, Cooling Flow Clusters).
  • Particle Astrophysics: Pulsars, Anomalous Pulsars, Neutron Stars, Quark
    Stars and Stellar Black Holes.
  • Astrobiology: Astrophysical Mechanisms of Mass Extinctions; Solar Activity
    and Cosmic Rays Effects on Terrestrial Biology and Climate.

 

Research  Experience
  • Nuclear Physics
  • Plasma Physics
  • Particle Physics
  • Astrophysics and Cosmology

 

Main Original Ideas and Achievements
  • Nuclear Physics
    • Diffraction Model For Direct Nuclear Reactions.
    • Semiclassical Models For Low and High Energy Heavy Ion Collisions.

  • Plasma Physics
    • Fusion chain reaction in a cold matter (with Y. Grunzweig, A. Peres, M.
      Revzen and A. Ron).

  • Particle Physics
    • Diffraction model for elastic Scattering (with Y. Dothan, M. Kugler and S.
      Nussinov).
    • Absorption model for two body reactions.
    • First demonstration of particle properties from the quark model (with V. F.
      Weisskopf).
    • Quark model for high energy particle-nucleus and nucleus-nucleus
      collisions (with Y. Afek, G. Berlad and G. Eilam).

  • Particle Astrophysics
    • Analytic calculation of the atmospheric neutrino background.
    • Terrestrial tests of the neutrino oscillations solution to the solar neutrino
      problem (with A. Mann).
    • The day/night effect for solar neutrinos (With A. Mann).
    • Predicting and alerting IMB and Kamiokande proton decay detectors of the
      neutrino signal from SN1987a (with J. Bahcall and T. Piran).
    • Limits on neutrino properties from the neutrino signal from SN1987A.
    • Neutrino anihilation role in core collapse SN explpsions (with J. Goodman
      and S. Nussinov).
    • GRBs from neutrino annihilation in neutron star mergers (with J. Goodman
      and S. Nussinov).

  • Astrophysics
    • A cosmic GRB-SN association (with B. Kozlowski, S. Nussinov and R. Ramaty).
    • A GRB-cosmic rays association (with B. Kozlowski, S. Nussinov and R. Ramaty).
    • Jetted GRBs from accretion induced stellar collapse and from mergers of
      neutron stars (with N. Shaviv).
    • Collimated afterglows from jetted GRBs.
    • GRB origin of Galactic cosmic rays (with R. Plaga).
    • The cannonball model of GRBs (with A. De Rujula).
    • The cannonball model of GRB afterglows (with S. Dado and A. De Rujula).
    • Afterglow Evidence for the GRB-SN association
      (with S. Dado and A. De Rujula).
    • A heat source of cooling flow clusters
      (with S. Colafrancesco and A. De Rujula).
    • Solution of the cosmic-ray origin puzzle (with A De Rujula).
    • A unified theory of high energy astrophysical phenomena (with A. De Rujula).

  • Cosmology
    • Long distance tests of general relativity.
    • A cosmic MeV neutrino background from past supernova.
    • A cosmic high energy neutrino background from AGN (with N. Shaviv).
    • A cosmic-ray origin of the extragalactic gamma ray background
      (with A. De Rujula).

  • Astrobiology
    • Terrestrial life extinctions by Galactic GRBs (with A. Laor and N. Shaviv).




Images of the fading optical afterglow of the gamma ray burst (GRB) 030329 that took place on March 29, 2003 taken by the very large telescope (VLT) of the European Southern Observatory (ESO) in Chille on April 3,2003 and May 1,2003. The image taken on May 1 is dominated by an underlying supernova which produced the GRB. The discovery of the underlying supernova SN203dh convinced the majority of the astrophysicists community that ``long-duration'' GRBs are produced by highly relativistic jets as long advocated by the Cannonball model of GRBs (Dar and De Rujula 2000 and Dado, Dar and De Rujula 2002). The underlying supernova was first discovered spectroscopically in the fading afterglow of GRB 0302329 by Stanek et al. (astro-ph/0304173) 10 days after the GRB took place. The observational discovery and its date was predicted before it was made by Dado, Dar and De Rujula from their study of the early afterglow of GRB 030329 (astro-ph/0304106).  The discovery that long duration GRBs are produced in core collapse supernova explosions was chosen by Science as one of the top 10 scientific discoveries in the year 2003.

Observed spectrum (thin line) of the optical light from GRB 030329/SN2003dh  at redshif z=0.1685, at t=25.8 days after burst. The model spectrum (thick line) consists of 39% continuum and 61% SN1998bw from 6 days after maximum. The figure is from Matheson et al.  astro-ph/0307435.




A one million second image of the expanding supernova remnant Cassiopeia A, obtained by the NASA X-ray satellite chandra. The remnant   was produced by the explosion of a massive star. Its bright outer X-ray ring (green), ten light years in diameter, is produced by the collision of the leading high speed ejecta from the explosion with the surrounding interstellar gas. In its rest frame the ejecta is bombarded by high speed incident electrons and nuclei (of the interstellar medium), and like in a Roentgen machine, they produce X-rays through bremsstrahlung and through line emission from excited atoms. A large jet-like structure that protrudes beyond the spherical ejecta can be seen in the upper left. In the accompanying image, specially processed to highlight silicon ions, a counter-jet can be seen on the lower right. They suggest that in the explosion that created Cassiopeia A, highly relativistic narrowly collimated jets were fired and  produced gamma-ray bursts which were beamed along their direction of motion.