  Gamma-Ray Bursts (GRBs) are the must violent explosions after the Big-Bang.
Their high energy radiation can potentially carry information about the most
inner part of the accretion disk of a collapsing star, ionize the surrounding
material in the host galaxy and thereby influence the process of star formation
specially in the dense environment at high redshifts. They can also have a
significant contribution in the formation of high energy cosmic-rays. Here we
present new simulations of GRBs according to a dynamically consistent
relativistic shock model for the prompt emission, with or without the presence
of an magnetic field. They show that the properties of observed bursts are well
reproduced by this model up to GeV energies. They help to better understand GRB
phenomenon, and provide an insight into characteristics of relativistic jets
and particle acceleration which cannot yet be simulated with enough precision
from first principles.
