Surrogate Lagrangians for Variational Integrators: High Order Convergence with Low Order Schemes
This work provides a method to improve the accuracy of variational integrators without increasing computational cost, benefiting simulations of Hamiltonian systems in physics and engineering.
The paper introduces surrogate Lagrangians for variational integrators, achieving fourth-order convergence with second-order complexity, and extends the method to constrained systems and arbitrary-order accuracy.
Variational integrators are momentum-preserving and symplectic numerical methods used to propagate the evolution of Hamiltonian systems. In this paper, we introduce a new class of variational integrators that achieve fourth-order convergence despite having the same integration scheme as traditional second-order variational integrators. The new class of integrators are created by replacing a dynamical system's Lagrangian in the variational integration algorithm with its surrogate Lagrangian. By incorporating the surrogate Lagrangian the propagation errors induced by variational integrators, up to a given order, are eliminated. Furthermore, no assumption on the Lagrangian's structure is made and, therefore, the proposed approach is applicable to a large range of dynamical systems. In addition, surrogate variational integrators are also constructed for Hamiltonian systems subjected to holonomic constraints and external forces. Finally, the methodology is extended to derive higher-order surrogate variational integrators that achieve an arbitrary order of accuracy but retain second-order complexity in the integration scheme. Several numerical experiments are presented to demonstrate the efficacy of our approach.