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## Extreme Energy Cosmic Rays: Bottom-up vs. Top-down scenarii

### Abstract

LaTex, 16 pages, 2 .eps figures. The annihilation scenario (Wimpzillas) is included and the discussion on gamma ray bursts improved. Based on lectures at the Fourth International Workshop on New Worlds in Astroparticle Physics' in Faro, Portugal, September 2002, at the 9th Course on Astrofundamental Physics of the Chalonge School, Palermo, Italia, September 2002 and at the SOWG EUSO meeting, Roma, Italia, November 2002We present an overview on extreme energy cosmic rays (EECR) and the fundamental physics connected with them. The top-down and bottom-up scenarii are contrasted. We summarize the essential features underlying the top-down scenarii for EECR, namely, the lifetime and the mass {\bf imposed} to the heavy relics whatever they be: topological and non-topological solitons, X-particles, cosmic defects, microscopic black-holes, fundamental strings. An unified formula for the quantum decay rate of all these objects was provided in hep-ph/0202249. The key point in the top-down scenarii is the necessity to {\bf adjust} the lifetime of the heavy object to the age of the universe. The natural lifetimes of such heavy objects are, however, microscopic times associated to the GUT energy scale (sim 10^{-28} sec. or shorter); such heavy objects could have been abundantly formed by the end of inflation and it seems natural they decayed shortly after being formed. The arguments produced to {\bf fine tune} the relics lifetime to the age of the universe are critically analyzed. The annihilation scenario (Wimpzillas') is analyzed too. Top-down scenarii based on networks of topological defects are strongly disfavored at the light of the recent CMB anisotropy observations. We discuss the acceleration mechanisms of cosmic rays,their possible astrophysical sources and the main open physical problems and difficulties in the context of bottom-up scenarii, and we conclude by outlining the expectations from future observatories like EUSO and where the theoretical effort should be placed

Topics: [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.GRQC] Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.HPHE] Physics [physics]/High Energy Physics - Phenomenology [hep-ph], [PHYS.HTHE] Physics [physics]/High Energy Physics - Theory [hep-th]
Publisher: Kluwer
Year: 2003
OAI identifier: oai:HAL:hal-00102603v1
Provided by: Hal-Diderot