Causal Hamilton-Jacobi-Bellman Equations for Anticipative Stochastic Optimal Control
Peter Bank, Franziska Bielert
TL;DR
The paper develops a causal Hamilton-Jacobi-Bellman framework for anticipative stochastic control with rough-path dynamics, where the controller can see the future Brownian motion over a moving horizon. By merging the martingale optimality principle with a pathwise, Dupire-based functional Itô calculus, it derives a deterministic HJB in terms of causal derivatives and a transport term reflecting anticipativity, linking the value function $v$ to a path-dependent map $u$. A verification theorem and a regular-value analysis are provided, leveraging conditional distributions and pathwise quadratic variation to establish both sufficiency and necessity of the HJB under suitable regularity. The approach is illustrated through insider-investment and front-running-style examples, demonstrating how anticipative information can be incorporated into a robust rough-path control framework with concrete HJB characterizations.
Abstract
We consider a stochastic optimal control problem where the controller can anticipate the evolution of the driving noise over some dynamically changing time window. The controlled state dynamics are understood as a rough differential equation. We combine the martingale optimality principle with a functional form of Itô's formula to derive a Hamilton-Jacobi-Bellman (HJB) equation for this problem. This HJB equation is formulated in terms of Dupire's functional derivatives and involves a transport equation arising from the anticipativity of the problem.
