Hermitian Positive Semidefinite Matrices Whose Entries Are 0 Or 1 in Modulus

Daniel Hershkowitz, Michael Neumann, Hans Schneider

We show that a matrix is a Hermitian positive semidefinite matrix whose nonzero entries have modulus 1 if and only if it similar to a direct sum of all $1^{\prime }s$ matrices and a 0 matri…