Calvo, M. (calvo@unizar.es) ; Laburta Santamaría, María Pilar (laburta@unizar.es) ; Montijano, Juan I. (monti@unizar.es) ; Rández, Luis (randez@unizar.es)

Resumen: The construction of new explicit Runge{Kutta methods taking into account, not only their accuracy, but also the preservation of Quadratic Invariants (QIs) is studied. An expression of the error of conservation of a QI by a Runge{Kutta method is given, and a new six{stage for- mula with classical order four and seventh order of QI{conservation is obtained by choosing their coe±cients so that they minimize both local and conservation errors. This formula, as well as other ones derived by Aubry and Chartier [1] and some standard formulas, have been tested with several problems with quadratic and general invariants. It is shown that the new fourth{order explicit method preserves much better the qualitative properties of the °ow than standard fourth{ order methods at the price of two extra function evaluations per step. Furthermore, it is a practical and e±cient alternative to the standard implicit methods required for a complete preservation of QIs.

Idioma: Inglés
Departamento: Matemática Aplicada

Palabra(s) clave: Runge-Kutta Methods ; Quadratic Invariants ; Pseudo-Symplectic Methods