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A novel second order scheme with one step for forward backward stochastic differential equations

Qiang Han, Shihao Lan, Quanxin Zhu

TL;DR

The paper tackles numerical solution of decoupled forward-backward stochastic differential equations (FBSDEs) by introducing a novel explicit one-step second-order discretization parameterized by $α ∈ (0,1]$, which recovers Crank–Nicolson when $α=1$. It provides a stability analysis and local truncation error bounds via Itô–Taylor expansions, leading to a global error bound that confirms second-order convergence. Numerical experiments on a scalar BSDE and a FitzHugh–Nagumo–type FBSDE validate the theory, showing near–two order convergence across different $α$ values and demonstrating that the method remains efficient and fully explicit for both $Y$ and $Z$. The work offers a practical, high-order alternative to multistep or implicit schemes and lays groundwork for constructing higher-order one-step methods.

Abstract

In this paper, we present a novel explicit second order scheme with one step for solving the forward backward stochastic differential equations, with the Crank-Nicolson method as a specific instance within our proposed framework. We first present a rigorous stability result, followed by precise error estimates that confirm the proposed novel scheme achieves second-order convergence. The theoretical results for the proposed methods are supported by numerical experiments.

A novel second order scheme with one step for forward backward stochastic differential equations

TL;DR

The paper tackles numerical solution of decoupled forward-backward stochastic differential equations (FBSDEs) by introducing a novel explicit one-step second-order discretization parameterized by , which recovers Crank–Nicolson when . It provides a stability analysis and local truncation error bounds via Itô–Taylor expansions, leading to a global error bound that confirms second-order convergence. Numerical experiments on a scalar BSDE and a FitzHugh–Nagumo–type FBSDE validate the theory, showing near–two order convergence across different values and demonstrating that the method remains efficient and fully explicit for both and . The work offers a practical, high-order alternative to multistep or implicit schemes and lays groundwork for constructing higher-order one-step methods.

Abstract

In this paper, we present a novel explicit second order scheme with one step for solving the forward backward stochastic differential equations, with the Crank-Nicolson method as a specific instance within our proposed framework. We first present a rigorous stability result, followed by precise error estimates that confirm the proposed novel scheme achieves second-order convergence. The theoretical results for the proposed methods are supported by numerical experiments.
Paper Structure (6 sections, 6 theorems, 89 equations, 3 figures, 6 tables, 1 algorithm)

This paper contains 6 sections, 6 theorems, 89 equations, 3 figures, 6 tables, 1 algorithm.

Key Result

Theorem 3.1

Suppose the assumptions (i)-(iii) and $f(t,Y_t,Z_t)\in C_b^3$ hold. Then for a sufficiently small step size $h_t$, we have where $C$ denotes a positive constant.

Figures (3)

  • Figure 1: The plot of $\text{err}_{y}$ against time interval $\Delta t$ in Example 1.
  • Figure 2: Log-log plot of $\text{err}_{y}$ against time interval $\Delta t$ in Example 2 ($a=-0.5$, and $x_0=1$).
  • Figure 3: Log-log plot of $\text{err}_{y}$ against time interval $\Delta t$ in Example 2 ($a=-1$, and $x_0=1.5$).

Theorems & Definitions (6)

  • Theorem 3.1
  • Proposition 4.1
  • Lemma 4.2
  • Lemma 4.3
  • Lemma 4.4
  • Theorem 4.5