Feller-continuous process

In mathematics, a Feller-continuous process is a continuous-time stochastic process for which the expected value of suitable statistics of the process at a given time in the future depend continuously on the initial condition of the process. The concept is named after Croatian-American mathematician William Feller.

Let X : [0, +∞) × Ω → Rⁿ, defined on a probability space (Ω, Σ, P), be a stochastic process. For a point x ∈ Rⁿ, let P^x denote the law of X given initial value X₀ = x, and let E^x denote expectation with respect to P^x. Then X is said to be a Feller-continuous process if, for any fixed t ≥ 0 and any bounded, continuous and Σ-measurable function g : Rⁿ → R, E^x[g(X_t)] depends continuously upon x.

• Every process X whose paths are almost surely constant for all time is a Feller-continuous process, since then E^x[g(X_t)] is simply g(x), which, by hypothesis, depends continuously upon x.
• Every Itô diffusion with Lipschitz-continuous drift and diffusion coefficients is a Feller-continuous process.