ALGEBRAIC DECAY OF VELOCITY FLUCTUATIONS IN A CONFINED FLUID

Computer simulations of a colloidal particle suspended in a fluid conf ined by rigid walls show that, at long times, the velocity correlation function decays with a negative algebraic tail. The exponent depends on the confining geometry, rather than the spatial dimensionality. We can account for the tail by using a simple mode-coupling theory which exploits the fact that the sound wave generated by a moving particle b ecomes diffusive.