BAND-STRUCTURE OF THE HAMILTONIAN MATRIX OF A REAL CHAOTIC SYSTEM - THE CE ATOM

The properties and structure of the Hamiltonian matrix of a realistic many-body quantum chaotic system (the rare-earth atom of Ce) are analy zed and compared with those assumed in band random matrix theories. Th e sparsity of the matrix and the behavior of the mean squared matrix e lements [H-ij(2)](\i-j\=Delta) as function of the distance \i-j\ from the diagonal are studied. Fitting [H-ij(2)](\i-j\=Delta) with the expo nent H-0(2) exp(-Delta/b) yields the bandwidths of b=54 and 79 for the matrices of J(pi) = 4(+), and 4(-) states, respectively.