Langevin Theory of Anomalous Brownian Motion Made Simple

Autor/inn/en	Tothova, Jana; Vasziova, Gabriela; Glod, Lukas; Lisy, Vladimir
Titel	Langevin Theory of Anomalous Brownian Motion Made Simple
Quelle	In: European Journal of Physics, 32 (2011) 3, S.645-655 (11 Seiten) PDF als Volltext Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	0143-0807
DOI	10.1088/0143-0807/32/3/002
Schlagwörter	Motion; Problem Solving; Science Instruction; Physics; Scientific Concepts; Theories; Science Experiments; Equations (Mathematics); College Science; Graduate Study; Molecular Structure; Water + Suchen Sie Ihr Suchwort? Bewegungsablauf; Problemlösen; Teaching of science; Science education; Natural sciences Lessons; Naturwissenschaftlicher Unterricht; Physik; Theory; Theorie; Equations; Mathematics; Gleichungslehre; Aufbaustudium; Graduiertenstudium; Hauptstudium; Wasser
Abstract	During the century from the publication of the work by Einstein (1905 "Ann. Phys." 17 549) Brownian motion has become an important paradigm in many fields of modern science. An essential impulse for the development of Brownian motion theory was given by the work of Langevin (1908 "C. R. Acad. Sci.", Paris 146 530), in which he proposed an 'infinitely more simple' description of Brownian motion than that by Einstein. The original Langevin approach has however strong limitations, which were rigorously stated after the creation of the hydrodynamic theory of Brownian motion (1945). Hydrodynamic Brownian motion is a special case of 'anomalous Brownian motion', now intensively studied both theoretically and in experiments. We show how some general properties of anomalous Brownian motion can be easily derived using an effective method that allows one to convert the stochastic generalized Langevin equation into a deterministic Volterra-type integro-differential equation for the mean square displacement of the particle. Within the Gibbs statistics, the method is applicable to linear equations of motion with any kind of memory during the evolution of the system. We apply it to memoryless Brownian motion in a harmonic potential well and to Brownian motion in fluids, taking into account the effects of hydrodynamic memory. Exploring the mathematical analogy between Brownian motion and electric circuits, which are at nanoscales also described by the generalized Langevin equation, we calculate the fluctuations of charge and current in "RLC" circuits that are in contact with the thermal bath. Due to the simplicity of our approach it could be incorporated into graduate courses of statistical physics. Once the method is established, it allows bringing to the attention of students and effectively solving a number of attractive problems related to Brownian motion. (As Provided).
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Update	2017/4/10