BOUNDARY-CONDITIONS AT THE MOBILITY EDGE

It is shown that the universal behavior of the spacing distribution of nearest energy levels at the metal-insulator Anderson transition is i ndeed dependent on the boundary conditions. The spectral rigidity Sigm a(2)(E) also depends on the boundary conditions, but this dependence v anishes at high energy E. This implies that the multifractal exponent D-2 of the participation ratio of wave functions in the bulk is not af fected by the boundary conditions.