In this paper we consider the random walk approximation of the solution of a Markovian BSDE whose terminal condition is a locally Hölder continuous function of the Brownian motion. We state the rate of the L 2 -convergence of the approximated solution to the true one. The proof relies in part on growth and smoothness properties of the solution u of the associated PDE. Here we improve existing results by showing some properties of the second derivative of u in space.Keywords : Backward stochastic differential equations, numerical scheme, random walk approximation, speed of convergence MSC codes : 65C30 60H35 60G50 65G99
IntroductionLet (Ω, F, P) be a complete probability space carrying the standard Brownian motion B = (B t ) t≥0 and assume (F t ) t≥0 is the augmented natural filtration. We consider the following backward stochastic differential equation (BSDE for short)where f is Lipschitz continuous and g is a locally α-Hölder continuous and polynomially bounded function (see (3)). In this paper we are interested in the L 2 -convergence of the numerical approximation of (1) by using a random walk. First results dealing with the numerical approximation of BSDEs date back to the late 1990s. Bally (see [2]) was the first to consider this problem by introducing random discretization, namely the jump times of a Poisson process. In his PhD thesis, Chevance (see [17]) proposed the following discretization y k = E(y k+1 + hf (y k+1 )|F n k ), k = n − 1, · · · , 0, n ∈ N * and proved the convergence of (Y n t ) t := (y [t/h] ) t to Y . At the same time, Coquet, Mackevičius and Mémin [18] proved the convergence of Y n by using convergence of filtrations, still in the case of