title: Direct measurement of shear-induced cross-correlations of Brownian motion.
abstract: Shear-induced cross-correlations of particle fluctuations perpendicular and along streamlines are investigated experimentally and theoretically. Direct measurements of the Brownian motion of micron-sized beads, held by optical tweezers in a shear-flow cell, show a strong time asymmetry in the cross-correlation, which is caused by the non-normal amplification of fluctuations. Complementary measurements on the single particle probability distribution substantiate this behavior and both results are consistent with a Langevin model. In addition, a shear-induced anticorrelation between orthogonal random displacements of two trapped and hydrodynamically interacting particles is detected, having one or two extrema in time, depending on the positions of the particles.
authors.affiliation: Technische Physik, Universität des Saarlandes, 66041 Saarbrücken, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Ziehl
authors.forename: J
authors.initials: J
authors.lastname: Bammert
authors.forename: L
authors.initials: L
authors.lastname: Holzer
authors.forename: C
authors.initials: C
authors.lastname: Wagner
authors.forename: W
authors.initials: W
authors.lastname: Zimmermann