  We study by means of renormalization group techniques the effect that on the
two-dimensional electron liquid may have the van Hove singularities observed
experimentally in the copper-oxide superconductors. We find significant
deviations from Fermi liquid behavior, that lead to the appearance of an
unstable fixed point in the renormalization group flow of the effective
coupling constant. Besides the attenuation of electron quasiparticles already
known on phenomenological grounds, our approach is able to explain the
reduction in the dispersion of the band as well as the pinning of the Fermi
level near the singularity, as observed in the photoemission experiments.
