Introduction: 100 years of Brownian motion.

In the year 1905 Albert Einstein published four pap that raised him to a giant in the history of science. Th works encompass the photo-electric effect sfor which he ob tained the Nobel prize in 1921 d, his first two papers onsspeciald relativity theory, and his first paper on Brownian m tion, entitled “Über die von der molekularkinetisch Theorie der Wärme geforderte Bewegung von in ruhen Flüssigkeiten suspendierten Teilchen” ssubmitted on 11 Ma 1905d. Thanks to Einstein’s intuition, the phenomenon served by the Scottish botanist Robert Brown 2 i 1827—a little more than a naturalist’s curiosity—becomes the k stone of a fully probabilistic formulation of statistical m chanics and a well-established subject of physical inves tion which we celebrate in this Focus Issue entitled—for reason—“100 Years of Brownian Motion.” Although written in a dated language, Einstein’s first per on Brownian motion already contains the cornerston the modern theory of stochastic processes. The author out using arguments of thermodynamics and the conce osmotic pressure of suspended particles to evaluate a p diffusion constant by balancing a diffusion current wit drift currentsthrough Stokes’ lawd. In doing so, he obtains relation between two transport coefficients: the particle fusion constant and the fluid viscosity, or friction. This re tion, known as the Einstein relation, 3 was later generalized terms of the famous fluctuation-dissipation theorem Callen and Welton 4 and by the linear response theory Kubo. A much clearer discussion of Einstein’s argume can be found in his thesis work, accepted by the Unive of Zurich in July 1905, which he submitted for publicatio 6