Convergence of adaptive discontinuous Galerkin and $C^0$-interior penalty finite element methods for Hamilton--Jacobi--Bellman and Isaacs equations
Ellya L. Kawecki, Iain Smears
TL;DR
The paper addresses convergence of adaptive broad-family DG and $C^0$-IP methods for fully nonlinear second-order HJB and Isaacs equations under Cordes coefficients in two and three dimensions. It introduces an intrinsic limit-space framework that characterizes the limit behavior of nonconforming finite element sequences without requiring nested conforming spaces, and it extends the Cordes-renormalized operator $F_{\gamma}$ to a robust variational setting. The authors prove plain convergence of the adaptive schemes and establish reliability/efficiency of a posteriori estimators, along with strong properties of the limit problem, including Hessian symmetry and approximation by quadratic polynomials. The results provide a rigorous foundation for stable, efficient adaptive methods for fully nonlinear PDEs in applications such as stochastic control and differential games, while offering a general framework for nonconforming adaptivity beyond HJB/Isaacs problems.
Abstract
We prove the convergence of adaptive discontinuous Galerkin and $C^0$-interior penalty methods for fully nonlinear second-order elliptic Hamilton--Jacobi--Bellman and Isaacs equations with Cordes coefficients. We consider a broad family of methods on adaptively refined conforming simplicial meshes in two and three space dimensions, with fixed but arbitrary polynomial degrees greater than or equal to two. A key ingredient of our approach is a novel intrinsic characterization of the limit space that enables us to identify the weak limits of bounded sequences of nonconforming finite element functions. We provide a detailed theory for the limit space, and also some original auxiliary functions spaces, that is of independent interest to adaptive nonconforming methods for more general problems, including Poincaré and trace inequalities, a proof of density of functions with nonvanishing jumps on only finitely many faces of the limit skeleton, approximation results by finite element functions and weak convergence results.
