Weak convergence analysis in the particle limit of the McKean--Vlasov equations using stochastic flows of particle systems
Abdul-Lateef Haji-Ali, Håkon Hoel, Raúl Tempone
TL;DR
The paper addresses the weak convergence rate of particle approximations to the McKean-Vlasov equation. It develops a framework based on the Kolmogorov backward equation for the particle system and uses stochastic flows together with dual functions to bound the weights in a dual-weighted residual representation, thereby establishing a weak-error rate of $O(n^{-1})$. The main result is proved under Lipschitz conditions on the drift $a$, diffusion $\sigma$, and interaction kernels $\kappa_1,\kappa_2$, together with a priori moment bounds for the MV solution. The approach generalizes prior results that required $\kappa_2\equiv 0$ and provides a pathway to relax assumptions through numerical evidence, with explicit bounds on the empirical kernel deviations and moment growth. Numerical experiments corroborate the rate and suggest that some regularity assumptions may be relaxable.
Abstract
We present a proof showing that the weak error of a system of $n$ interacting stochastic particles approximating the solution of the McKean-Vlasov equation is $\mathcal O(n^{-1})$. Our proof is based on the Kolmogorov backward equation for the particle system and bounds on the derivatives of its solution, which we derive more generally using the variations of the stochastic particle system. The convergence rate is verified by numerical experiments, which also indicate that the assumptions made here and in the literature can be relaxed.
