  Preliminary results toward the analysis of the Hamiltonian structure of
multifield theories describing complex materials are mustered: we involve the
invariance under the action of a general Lie group of the balance of
substructural interactions. Poisson brackets are also introduced in the
material representation to account for general material substructures. A
Hamilton-Jacobi equation suitable for multifield models is presented. Finally,
a spatial version of all these topics is discussed without making use of the
notion of paragon setting.
