Symbolic Computation of Variational Symmetries in Optimal Control

Symbolic Computation in the Calculus of Variations: Determination of Symmetries and Conservation Laws (in Portuguese)

English version of abstract: The dynamic optimization problems treated by the calculus of variations are usually solved with the help of the 2nd order Euler-Lagrange differential equations. These equations are, generally speaking, nonlinear, and very hard to solve. One way to address the problem is to obtain conservation laws of lower order than those of the corresponding Euler-Lagrange equations. While in Physics and Economics the question of existence of conservation laws is treated in a rather natural way, because the application itself suggest the conservation laws (e.g., conservation of e…

Computing ODE Symmetries as Abnormal Variational Symmetries

We give a new computational method to obtain symmetries of ordinary differential equations. The proposed approach appears as an extension of a recent algorithm to compute variational symmetries of optimal control problems [Comput. Methods Appl. Math. 5 (2005), no. 4, pp. 387-409], and is based on the resolution of a first order linear PDE that arises as a necessary and sufficient condition of invariance for abnormal optimal control problems. A computer algebra procedure is developed, which permits to obtain ODE symmetries by the proposed method. Examples are given, and results compared with th…

Variational integrators for underactuated mechanical control systems with symmetries

Optimal control problems for underactuated mechanical systems can be seen as a higher-order variational problem subject to higher-order constraints (that is, when the Lagrangian function and the constraints depend on higher-order derivatives such as the acceleration, jerk or jounces). In this paper we discuss the variational formalism for the class of underactuated mechanical control systems when the configuration space is a trivial principal bundle and the construction of variational integrators for such mechanical control systems. An interesting family of geometric integrators can be defined…

Normal forms and gauge symmetries of local dynamics

A systematic procedure is proposed for deriving all the gauge symmetries of the general, not necessarily variational, equations of motion. For the variational equations, this procedure reduces to the Dirac-Bergmann algorithm for the constrained Hamiltonian systems with certain extension: it remains applicable beyond the scope of Dirac's conjecture. Even though no pairing exists between the constraints and the gauge symmetry generators in general non-variational dynamics, certain counterparts still can be identified of the first- and second-class constraints without appealing to any Poisson str…

平均场博弈方程的守恒律

Conservation laws of mean field games equations

本文研究平均场博弈方程组的守恒律，利用其变分结构，通过Noether定理从变分和散度对称性推导守恒律，并识别出具有额外对称性的特殊情形。

Maple Symbolic Computation in the Calculus of Variations

It is the aim of this work to identify and illustrate the potential and weaknesses of the computer algebra system Maple in the area of the Calculus of Variations: a classical area of mathematics that studies the methods for finding maximum and minimum values of functionals of integral type. Variational problems are usually solved with the help of the necessary optimality conditions of Euler-Lagrange, which are, in general, nonlinear and difficult second order differential equations to be solved. We show how the computer algebra system Maple can be useful in the determination and resolution of …