4 citations · 6 across the 9 of their papers we have counts for
11 papers
Proof of a conjecture on polynomials preserving nonnegative matrices
Raphael Loewy
We consider polynomials in R[x] which map the set of nonnegative (element-wise) matrices of a given order into itself. Let n be a positive integer and define P(n)= {p in R[x] : p(A…
On Faces of the set of Quantum Channels
Raphael Loewy
A linear map from into is called a quantum channel if it is completely positive and trace preserving. The set …
A Necessary Condition for the Spectrum of Nonnegative Symmetric Matrices
Raphael Loewy, Oren Spector
Let be a nonnegative symmetric matrix with eigenvalues . We show that if …
On the extreme points of quantum channels
Shmuel Friedland, Raphael Loewy
Let L(m,n) denote the convex set of completely positive trace preserving operators from C^{m x m} to C^{n x n}$, i.e quantum channels. We give a necessary condition for L in L(m,n)…
Power series with positive coefficients arising from the characteristic polynomials of positive matrices
Thomas J. Laffey, Raphael Loewy, Helena Šmigoc
Let A be an nxn (entrywise) positive matrix and let f(t)=det(I-t A). We prove that there always exists a positive integer N such that 1-f(t)^{1/N} has positive coefficients.
On the minimum rank of a graph over finite fields
Shmuel Friedland, Raphael Loewy
In this paper we deal with two aspects of the minimum rank of a simple undirected graph on vertices over a finite field $\FF_q$ with elements, which is denoted by $\mr(…