Discrete isothermic surfaces.
Divergences in formal variational calculus and boundary terms in Hamiltonian formalism
It is shown how to extend the formal variational calculus in order to incorporate integrals of divergences into it. Such a generalization permits to study nontrivial boundary problems in field theory on the base of canonical formalism.
Do all integrable equations satisfy integrability criteria?
Dynamical connections and non-autonomous lagrangian systems