| speaker: | Walter Goldburg University of Pittsburgh |
| time: | Friday, November 16, 11:40 - 12:05 |
Dangle your feet over the edge of a quay and look down on the moving water below. The flotsam often seen there coagulates in patches. In the experiments discussed here, the “flotsam” is replaced by an assembly of 50-micron particles that float on a large tank of water driven into a state of strong steady-state turbulence. As with the flotsam, the assembly of floaters form a compressible system and also exhibit coagulation. Amongst the surprising properties of the floaters is their entropy (S), or rather its rate of change, dS/dt. The measurements are compared with the predictions of a generalized version of the fluctuation-dissipation theorem (R. A. Ferrell, 1958). The measurements are compared with a generalized version of this theorem advanced by Gallavotti and Cohen (1995). It turns out that dS(x,t)/dt is equal to the (non-zero) divergence of the velocity field of the floaters .