Abstract. We consider extensions of the classical Fokker-Planck equation u t + Lu = ∇ · (u∇V (x)) on R d with L = −∆ and V (x) = 1 2 |x| 2 , where L is a general operator describing the diffusion and V is a suitable potential.
Introduction.We consider the initial value problem for the generalized FokkerPlanck equationwith a sufficiently regular potential V = V (x), u = u(x, t) and u 0 (x) ≥ 0. This equation generalizes the classical Fokker-Planck equationin two ways. First, the second order elliptic differential operator −∆ is replaced by a Markov diffusion operator L so that −L generates a positivity and mass preserving semigroup ewith ∇V (x) = x is replaced by a more general potential V which is large enough as |x| → ∞ so that V is confining.Our assumptions below will guarantee the existence of the unique steady state u ∞ = The paper is in final form and no version of it will be published elsewhere.[307] 308 P. BILER AND G. KARCH u ∞ (x) ≥ 0 of (1.1) with given M > 0,is the steady state for (1.3) for each M > 0, and u(t) tends to u ∞ at an exponential rate in all the L p norms, 1 ≤ p ≤ ∞, cf. [21].The motivations to study extensions (1.1) of (1.3) stem from the probability theory where Fokker-Planck equations are deeply connected with (nonlinear) stochastic differential equations driven by Gaussian and Lévy processes, see e.g. [17]. Another motivation is a study of the large time behavior of solutions of linear (as well as nonlinear) equations v t + Lv = 0 (1.5) with general diffusion operators L. Here, suitable space-time rescaling leads to an equation of type (1.1) with V (x) =