Dynamical symmetries of Markov processes with multiplicative white noise

• Autores: Aron, Camille; Barci, Daniel G.; Cugliandolo, Leticia F.; Arenas, Zochil González; Lozano, Gustavo Sergio
• Año de publicación: 2016
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Brownian Motion; Driven Diffusive Systems (Theory); Fluctuations (Theory); Stochastic Processes (Theory)
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We analyse various properties of stochastic Markov processes with multiplicative white noise. We take a single-variable problem as a simple example, and we later extend the analysis to the Landau-Lifshitz-Gilbert equation for the stochastic dynamics of a magnetic moment. In particular, we focus on the non-equilibrium transfer of angular momentum to the magnetization from a spin-polarised current of electrons, a technique which is widely used in the context of spintronics to manipulate magnetic moments. We unveil two hidden dynamical symmetries of the generating functionals of these Markovian multiplicative white-noise processes. One symmetry only holds in equilibrium and we use it to prove generic relations such as the fluctuation-dissipation theorems. Out of equilibrium, we take profit of the symmetry-breaking terms to prove fluctuation theorems. The other symmetry yields strong dynamical relations between correlation and response functions which can notably simplify the numerical analysis of these problems. Our construction allows us to clarify some misconceptions on multiplicative white-noise stochastic processes that can be found in the literature. In particular, we show that a first-order differential equation with multiplicative white noise can be transformed into an additive-noise equation, but that the latter keeps a non-trivial memory of the discretisation prescription used to define the former.
Fil: Aron, Camille. Katholikie Universiteit Leuven; Bélgica. University Of Princeton; Estados Unidos
Fil: Barci, Daniel G.. Universidade Do Estado de Rio Do Janeiro; Brasil
Fil: Cugliandolo, Leticia F.. Universite Paris Sorbonne; Francia
Fil: Arenas, Zochil González. Universidade Do Estado de Rio Do Janeiro; Brasil
Fil: Lozano, Gustavo Sergio. Universite Paris Sorbonne; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina