  We consider the separability of various joint states of D-dimensional quantum
systems, which we call "qudits." We derive two main results: (i) the
separability condition for a two-qudit state that is a mixture of the maximally
mixed state and a maximally entangled state; (ii) lower and upper bounds on the
size of the neighorhood of separable states surrounding the maximally mixed
state for N qudits.
