Physics Colloquium - Friday, Oct. 27th, 2006,
>>> Special Time: 3:30 P.M.! <<<

E300 Math/Science Center;
>>>AFTERWARDS: Reception at 4:45 P.M. in Room E200

Tom Lubensky
University of Pennsylvania

Rotational and Translational Diffusion of Rigid Rods

Rigid rods provide a useful theoretical idealization for the study of rotational dynamics and the formation of ordered liquid crystalline phases. In celebration of the 100th anniversary of Einstein's 1906 paper introducing the concept of rotational Brownian motion, this talk will discuss in detail recent experiments by the Penn group that provide the first direct measurements of coupled translational-rotational Brownian motion of rigid rods, including crossover from anisotropic to isotropic diffusion and the existence of non-Gaussian probability distributions. It will interpret these experiments in terms of a Langevin theory originally developed by F. Perrin. Finally, it will use the results for a single rod to motivate a theory for the dynamics of a two-dimensional granular gas composed of chiral "rattleback" particles and present experimental data confirming the broad predictions of the theory.