  We discuss the application of the two-band spin-dopon representation of the
t-J model to address the issue of the Fermi surface reconstruction observed in
the cuprates. We show that the electron no double occupancy (NDO) constraint
plays a key role in this formulation. In particular, the auxiliary lattice spin
and itinerant dopon degrees of freedom of the spin-dopon formulation of the t-J
model are shown to be confined in the emergent U(1) gauge theory generated by
the NDO constraint. This constraint is enforced by the requirement of an
infinitely large spin-dopon coupling. As a result, the t-J model is equivalent
to a Kondo-Heisenberg lattice model of itinerant dopons and localized lattice
spins at infinite Kondo coupling at all dopings. We show that mean-field
treatment of the large vs small Fermi surface crossing in the cuprates which
leaves out the NDO constraint, leads to inconsistencies and it is automatically
excluded form the t - J model framework.
