  The effect of fluctuations about the pi-flux mean field state for the undoped
high-temperature superconductors is investigated. It is shown that fluctuations
of the mean fields lead to a self-energy correction that doubles the band width
of the fermion dispersion in the lowest order. The dynamical mass generation is
associated with the self-energy effect due to the interaction mediated by the
Lagrange multiplier field, which is introduced to impose the constraint on the
fermions. A self-consistent picture about the mass generation and the prop-
agation of the Lagrange multiplier field without damping is proposed. The
antiferromagnetic long-range ordering is described without introducing an
additional repulsive interaction. The theory suggests a natural framework to
study spin disordered systems in which fermionic excitations are low-lying
excitations.

Strongly Correlated Electrons