  We study order parameter fluctuation effects in the superconducting state as
a possible precursor to the pseudogap phenomena.
  Using a low-energy effective theory in the d-wave BCS model, we
self-consistently calculate the single-particle properties. We find that the
fluctuations reduce the spectral gap, and the shape of the gap is deformed,
showing reduced slope of the gap at the nodes. We also show the
angle-dependence of the quasiparticle lifetime due to the fluctuations.
