Computational challenges in high-energy astrophysics

Supercomputers and grid networks are the basic instruments to elaborate and test physical models involving complex astrophysical phenomena. In this review some aspects of the field of high-energy astrophysics are illustrated that require large-scale computations due to the nonlinearities of the physical processes involved. They aim to understand fast dynamical phenomena, like stellar collapses, accretion onto black holes, launching and propagation of relativistic jets; high-energy phenomena involve a strong link between dynamics and micro physics and require a nonequilibrium treatment. A crucial point remains the validation of codes in regimes that are outside laboratory tests.