title: Langevin equation for systems with a preferred spatial direction.
abstract: In this paper, we generalize the theory of Brownian motion and the Onsager-Machlup theory of fluctuations for spatially symmetric systems to equilibrium and nonequilibrium steady-state systems with a preferred spatial direction, due to an external force. To do this, we extend the Langevin equation to include a bias, which is introduced by an external force and alters the Gaussian structure of the system's fluctuations. In addition, by solving this extended equation, we provide a physical interpretation for the statistical properties of the fluctuations in these systems. Connections of the extended Langevin equation with the theory of active Brownian motion are discussed as well.
authors.affiliation: The Rockefeller University, New York, New York 10065, USA.
authors.forename: Roman
authors.initials: R
authors.lastname: Belousov
authors.affiliation: The Rockefeller University, New York, New York 10065, USA.|Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: E G D
authors.initials: EG
authors.lastname: Cohen
authors.affiliation: Dipartimento di Scienze Matematiche and Graphene@Polito Lab Politecnico di Torino - Corso Duca degli Abruzzi 24, 10125, Torino, Italy.|INFN, Sezione di Torino - Via P. Giuria 1, 10125, Torino, Italy.|Kavli Institute for Theoretical Physics China, Chinese Academy of Sciences, Beijing 100190, China.|Malaysia Italy Centre of Excellence for Mathematical Sciences, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia.
authors.forename: Lamberto
authors.initials: L
authors.lastname: Rondoni