Ultrarelativistic SPH

In this paper the equations of motion of an ultrarelativistic gas are solved using the particle method SPH. The algorithm is based on a form of SPH which integrates the specific energy equation instead of the thermal energy equation and determines the dissipative terms along the lines of Riemann solvers. The resulting algorithms give good results for strongly relativistic shock tubes and they can handle collisions with relativistic velocities at feast 0.9999 the speed of light. Because the method uses a resolution which varies with time and in space it appears ideal for the simulation of collisions between ultrarelativistic nuclei. (C) 1997 Academic Press.