  Using a non-Hermitian Hamiltonian approach to open systems, we study the
interplay of disorder and superradiance in a one- and three-dimensional
Anderson model. Analyzing the complex eigenvalues of the non-Hermitian
Hamiltonian, a transition to a superradiant regime is shown to occur. As an
effect of openness the structure of eigenstates undergoes a strong change in
the superradiant regime: we show that the sensitivity to disorder of the
superradiant and the subradiant subspaces is very different; superradiant
states remain delocalized as disorder increases, while subradiant states are
sensitive to the degree of disorder.
