Variational and conservative principles in Rosen's theory of gravitation.
Variational theory of non-perfect relativistic fluids.
A basic question in General Relativity from the point of view of the general field theory is to obtain the Einstein equations coupled with the stress-energy-momentum tensor of a dissipative fluid from a variational principle. We believe that this problem, whose solution for perfect fluids is well known, has not been faced in a systematic way, maybe by the thought of a possible nonsense, for the concept of dissipation is believed to be incompatible with the essentially conservative character of the...