  Special solutions of the Hartree-Fock (HF) problem for Coulomb interacting
electrons, being described by a simple model of the Cu-O planes in La2CuO4, are
presented. One of the mean field states obtained, is able to predict some of
the basic properties of this material, such as its insulator character and the
antiferromagnetic order. The natural appearance of pseudogaps in some states of
this compound is also indicated by another of the HF states obtained. These
surprising results follow after eliminating spin and crystal symmetry
restrictions which are usually imposed on the single particle HF orbitals, by
means of employing a rotational invariant formulation of the HF scheme which
was originally introduced by Dirac. Therefore, it is exemplified how, up to now
being considered strong correlation effects, can be described by improving the
HF solution of the physical systems. In other words, defining the correlation
effects as such ones shown by the physical system and which are not predicted
by the best HF (lowest energy) solution, allows to explain currently assumed as
strong correlation properties, as simple mean field ones. The discussion also
helps to clarify the role of the antiferromagnetism and pseudogaps in the
physics of the HTSC materials and indicates a promising way to start
conciliating the Mott and Slater pictures for the description of the transition
metal oxides and other strongly correlated electron systems.
