Seminarium Zakładu Mechaniki i Fizyki Płynów The role of orientational Brownian motion in dispersive media prof. Jones, AMAS visiting professor , University of London, UK środa, 28 maja 2003

First of 6 lectures given on 28.05 (r. 100), 29.05, 2.06, 9.06, 16.06 and 23.06 (11:00, r. 108). Summary: Orientational Brownian motion plays a significant role in the dynamics of colloid suspensions and a dominant role in the case of ferrofluids and liquid crystals. The microscopic dynamics of such systems on the time-scale of Brownian motion is described by a Smoluchowski equation for the many-body distribution function. At this level, hydrodynamic interactions and dipole-dipole interactions play a role as well as external electric, magnetic and shear fields. Both tracer and collective rotational diffusion lead to important experimental observations on these systems. Depolarized light scattering, the relaxation of polarization and of the Kerr effect order parameter are macroscopic manifestations of this microscopic dynamics. The linear and non-linear response of such systems to oscillating external fields will be discussed on the basis of the Smoluchowski dynamics and compared with macroscopic effective field descriptions.