We give a necessary and sufficient condition for the existence of a local
solution of the inverse problem of calculus of variations in terms of the
identical vanishing of the variation of a functional on an extended space (with
the number of independent variables increased by one), and explain its relation
with the classical Helmholtz criterion using the de Rham complex on an
infinite-dimensional space of fields.
@article{0308179,
author = {Voronov, Theodore},
title = {An alternative form of the Helmholtz criterion in the inverse problem of
calculus of variations},
journal = {arXiv},
volume = {2003},
number = {0},
year = {2003},
language = {en},
url = {http://dml.mathdoc.fr/item/0308179}
}
Voronov, Theodore. An alternative form of the Helmholtz criterion in the inverse problem of
calculus of variations. arXiv, Tome 2003 (2003) no. 0, . http://gdmltest.u-ga.fr/item/0308179/