|  Fokker-Planck Equation | 
In General > s.a. Kramers
  Equation; stochastic processes.
  * Idea: An equation
    describing stochastic diffusion processes, or the time evolution of
    a non-equilibrium probability distribution.
  * More general formulation:
    The continuity equation
∂t ρ = − ∂a J a
applied to the stochastic evolution of a system on a manifold M of states, where ρ is a scalar density interpreted as probability density, and J a = ρ va − ∂b (ρKab) the probability current, with
va := limt → 0 t−1 ∫ p(ξ; x, t) ξa dξ ,
Kab := limt → 0 t−1 ∫ p(ξ; x, t) ξa ξb dξ ,
    where p(ξ; x, τ)
    is the probability that the system will evolve from x to x
    + ξ in a time τ; we assume that similar expressions with
    more ξs vanish; notice that v does not transform like a vector.
  * Applications: It is a central
    equation in the theory of brownian motion; Also used, e.g., by astronomers to find
    the general evolution of the orbits of stars in clusters or galaxies, and by population
    geneticists to describe random genetic drift.
  * Note: In the theory of continuous-time,
    continuous-state Markov processes it is also known as the Kolmogorov forward equation.
References > s.a. brownian motion; phase transitions.
  @ Texts: Papoulis 65;
    Soize 94 [non-linear];
    Risken 96.
  @ General articles:
    Desloge AJP(63)apr;
    Miyazawa JMP(99),
    JMP(00) [Green function];
    Wei JPA(00) [approach to solution];
    Kleinert AP(01) [from the forward-backward path integral];
    Sparber et al mp/02 [quantum, long-time behavior];
    Lo PLA(03) [propagator];
    Oron & Horwitz mp/03 [covariant Brownian motion];
    Lubashevsky et al mp/06 [boundary conditions];
    Lucia PhyA(13) [and entropy generation];
    Ryter a1403 [uniqueness].
  @ Approaches: Jafari & Aminataei PS(09) [homotopy perturbation method];
    Verevkin TMP(11) [Euler-Darboux transformation and solutions].
  @ Non-linear: Donoso et al JPA(99) [short-time propagator];
    Kiessling & Lancellotti TTSP(04)mp-conf;
    Plyukhin PhyA(05) [higher-order corrections];
    Donoso et al JPA(05),
    Donoso & Salgado JPA(06) [propagator];
    Tsekov IJTP(09)-a0808.
  @ Quantum version: Neumann & Sparber CMS(07)-a0707 [for bosons and fermions].
  @ Fractional: Schertzer et al JMP(01)m.AP/04;
    Tarasov & Zaslavsky PhyA(08);
    Zhang & Chen PhyA(14) [stochastic stability].
  @ Other generalized: Chavanis PhyA(04) [generalized thermodynamics];
    Khan & Reynolds PhyA(05) [generalized Langevin dynamics];
    Rybicki ApJ(06)ap/05 [for resonance-line scattering];
    Alcántara & Calogero KRM(11)-a1011,
    JMP(13) [relativistic];
    > s.a. diffusion [in curved spacetime];
    heat equation [relativistic].
  > Related topics:
    see hamilton-jacobi theory;
    Maxwell-Boltzmann Distribution.
Online Resources > see Physics Daily page; Wikipedia Fokker-Planck equation page, and Kolmogorov backward equation page.
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