  The single-particle spectral properties of the two-dimensional t-J model in
the parameter regime relevant to cuprate high-temperature superconductors are
investigated using cluster perturbation theory. Various anomalous features
observed in cuprate high-temperature superconductors are collectively explained
in terms of the dominant modes near the Mott transition in this model. Although
the behavior of the dominant modes in the low-energy regime is similar to that
in the two-dimensional Hubbard model, significant differences appear near the
Mott transition for the high-energy electron removal excitations which can be
considered to primarily originate from holon modes in one dimension. The
overall spectral features are confirmed to remain almost unchanged as the
cluster size is increased from 4x4 to 6x6 sites by using a combined method of
the non-abelian dynamical density-matrix renormalization group method and
cluster perturbation theory.
