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Weekly Seminars for June 2010 Print E-mail

Thursday 3rd June 2010 - 4:00 P.M.

Università "La Sapienza" Roma - Aula Majorana (Physics Dept., Old Building - Ground Floor)

Speaker:  Prof. Elena Pian (INAF, Trieste Astronomical Observatory and Scuola Normale Superiore, Pisa)

Title: Gamma-Ray Bursts in the Fermi Era

Abstract: GRBs are the most energetic events in the Universe. They are strong emitters at all wavelengths, including the MeV-GeV range. THe EGRET instrument onboard CGRO (1991-2000) had detected a handful of these high energy counterparts, some of which were rather long-lived (hour timescale). The Fermi-LAT instrument and (in a smaller number of cases) the AGILE GRID instrument are now providing a sensitive view of the GRB behavior at MeV-GeV energies and have opened the opportunity of a thorough investigation. I will review the LAT and AGILE GRID results, and the most important theoretical consequences.

Thursday 10th June 2010 - 4:00 P.M.

Università "La Sapienza" Roma - Aula Majorana (Physics Dept., Old Building - Ground Floor)

Speaker:  Dr. Paul Romatschke (INT, University of Washington - USA)

Title: A new look at cold quark matter in compact stars

Abstract: Compact stars offer a unique window of cold nuclear matter in the regime of extremely high densities. In particular, it has long been speculated that "exotic" phases of nuclear matter, such as quark matter could exist in the core of neutron stars. Lacking the tools to solve QCD accurately for densities expected in compact stars, simple toy models such as the MIT bag model for the QCD equation of state have been state of the art for the past 30 years. In this talk, I will argue that one can do better than that by using recent results from perturbative QCD. In fact, matching modern quark matter to realistic hadronic equations of state, one can reproduce available observations of neutron stars without any fine-tuning of parameters. I will discuss the implications on the cold nuclear matter equation of state and present and future compact star observations.

Tuesday 29th June 2010 - 10:30 A.M.

ICRANet Pescara, Seminars Room

Speaker:  prof. Stanley Davis (University Bordeaux 1, France - Fulbright Scholar, United States Department of State)

Title: Proton Beam Instability Simulations of Energy Transfer in Gamma-ray Bursts via Laser Irradiation on CH–H+ Foil

Abstract: We propose an experiment probing the GRB environment representing collissionless shock formation arising from interaction of ejecta with the interstellar medium. The experiment proposed here may be adaptable to the study of supernova. Two-stream proton beam instability (e.g., Weibel-like) may explain key ingredients for Gamma-Ray Bursts (GRBs): amplified magnetic field, relativistic electron production and a power law energy distribution of gamma radiation. By using particle-in-cell simulations, we investigated the acceleration of a dense proton bunch to energies of tens of MeV. Moreover, we demonstrate that a part of the directed kinetic energy of a proton beam is converted into kinetic energy of electrons, ions, electric and magnetic fields in a collision with a secondary plasma target. A finite lifetime for the magnetic field is demonstrated, indicating a maximum for the GRB duration.

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