If one relies on IT, it is clear that, epistemologically, no
ARTICLE IN PRESS
168 S. Martinez et al. / Physica A 356 (2005) 167–171
additional thermodynamic notions are to be presupposed in advance. Notice that
predictions derived from the IT-formalism amply exceed the scope of themes that
conventional thermodynamics is able to deal with [1,2]. In order to obtain the first law,
the usual text-book approach [3] analyzes the variation of the internal energy U, which
is regarded as a functional of both (i) the density operator and (ii) the Hamiltonian.