We study the density of states (DOS) for disordered systems whose spectral statistics can be described by a Gaussian ensemble of almost diagonal Hermitian random matrices. The matrices have independent random entries $ H_{ i \geq j} $ with small off-diagonal elements: $ <|H_{ i \neq j}|^{ 2} > \ll <|H_{ ii}|^{ 2} > \sim 1 $. Using the recently suggested method of a { \it virial expansion in the number of interacting energy levels} (Journ.Phys.A { \bf 36}, 8265), we calculate the leading correction to the Poissonian DOS in the cases of the Gaussian Orthogonal and Unitary Ensembles. We apply the general formula to the critical power-law banded random matrices and the unitary Moshe-Neuberger-Shapiro model and compare DOS of these models.
Categories: cond-mat.dis-nn cond-mat.mes-hall cond-mat.stat-mech hep-th math-ph math.MP nlin.CD quant-ph