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"The search for gravitational waves"

Relatore: Massimo Cerdonio- INFN Section and Department of Physics, University of Padua, Italy

Aula Newton, Dipartimento di Fisica
20 Settembre 2006 ore 11.30

Gravitational waves are still eluding detection: we are still blind to the direct messages sent out and carried by one of the fundamental forces of Nature, just when it is so strong to exploit the full physics of GR, as in processes involving black-holes, and when it overcomes in strength all the other fundamental interactions, as in matter at extreme densities, as neutron stars. Presently the future of the research field looks bright. The resonant mass “bar” detectors AURIGA, EXPLORER and NAUTILUS in Europe, ALLEGRO in USA and NIOBE in Australia, have been operated for 4 years as a network, giving upper limits to the yearly rate of violent gw events in the Galaxy. Now a 2300 kg resonant bar, cooled at 4 K as AURIGA, is sensitive to a few hundred quanta of vibration and has a band 100 Hz wide around 950 Hz, enough, according to recent models, to detect the vibrations induced by gravitational waves from proto neutron star in Supernova core collapses in the Galaxy. A first generation of km baseline interferometric detectors, GEO 0.6 km and VIRGO 3km in Europe, two 4 km LIGO and one 2km LIGO in USA, and TAMA 0.3 km in Japan, is coming to operation, with much wider bands and higher sensitivities. They will make for a global network, which, as it is commonly accepted, after a substantial upgrade in the early 2010s, will start the “observatory phase” much waited for. DUAL acoustic detectors are under study to get wideband best sensitivities in the kHz frequency range, complementary to such upgrade interferometers, to look specifically to the merging and the vibrations of neutron stars and black-holes.