  Using a recently developed perturbative approach, which considers Hubbard
operators as fundamental excitations, we have performed electronic self-energy
and spectral function calculations for the $t-J$ model on the square lattice.
We have found that the spectral functions along the Fermi surface are
isotropic, even close to the critical doping where the $d$-density wave phase
takes place. Fermi liquid behavior with scattering rate $\sim \omega^2$ and a
finite quasiparticle weight $Z$ was obtained. $Z$ decreases with decreasing
doping taking low values for low doping. Results are compared with other ones,
analytical and numerical like slave-boson and Lanczos diagonalization finding
agreement. We discuss our results in the light of recent $ARPES$ experiments in
cuprates.
