title: Optimal modulation of a Brownian ratchet and enhanced sensitivity to a weak external force.
abstract: We studied the dynamics of a Brownian particle moving in a spatially anisotropic potential acted on by multiplicative temporal modulations so that V(x,t) = g(t)U(x). Using the concept of the "thermodynamic action," we show that the class of modulation that maximizes the flow is a square-wave in time. We also show that adding a weak, homogenous force F in synergy with the square-wave modulation can cause particles of slightly different size to move in opposite directions. The synergetic change in velocity caused by F can be much greater than the drift velocity that would be caused by F alone.
authors.affiliation: James Franck Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Tarlie
authors.forename: R D
authors.initials: RD
authors.lastname: Astumian
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D007700:Kinetics; D008956:Models, Chemical; D013816:Thermodynamics