The International Conference on
Secondary Calculus and Cohomological Physics,
Moscow, August 24 - August 31, 1997

Divergences as a grading of the formal variational calculus

Vladimir O. Soloviev

Abstract: It is shown that the new formula for the field theory Poisson brackets arise naturally in the extension of the formal variational calculus incorporating divergences. The linear spaces of local functionals, evolutionary vector fields, functional forms, multi-vectors and differential operators become graded with respect to divergences. The bilinear operations, such as the action of vector fields on functionals, the commutator of vector fields, the interior product of forms and vectors and the Schouten-Nijenhuis bracket are compatible with the grading. A definition of the adjoint graded operator is proposed and antisymmetric operators are constructed with the help of boundary terms. The fulfilment of the Jacobi identity for the new Poisson brackets is shown to be equivalent to vanishing of the Schouten-Nijenhuis bracket of the Poisson bivector with itself. It is demonstrated, as an example, that the second structure of the Korteweg-de Vries equation is not Hamiltonian with respect to the new brackets until special boundary conditions are prescribed.

Keywords: Hamiltonian formalism, field theory, Poisson brackets, boundary terms

Classification (MSC91): 58F05; 70G50, 58G20

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