A TEST OF THE PARTICLE PARADIGM IN N-BODY SIMULATIONS

We present results of tests of the evolution of small ''fluid elements '' in cosmological N-body simulations, to examine the validity of thei r treatment as particles. We find that even very small elements typica lly collapse along one axis while expanding along another, often to tw ice or more their initial comoving diameter. This represents a possibl e problem for high-resolution uses of such simulations.