Open questions with ultra-high energy cosmic rays

Abstract

We briefly discuss three aspects related to the origin of ultra-high energy cosmic rays (UHECRs) namely: 1) particle acceleration in astrophysical sources; 2) transition to an extragalactic origin; 3) spectrum and anisotropies at the highest energies.

6 pages. Invited Review Talk at the 2nd Workshop on TeV Particle Astrophysics, 28-31 August 2006 Madison, WI, USA

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