Perron-Frabenius Theorem. Let be a positive matrix. Then the following statements hold:
there is a real eigenvalue of such that any other eigenvalue of satisfies
(hence r is the spectral radius of );
there are a right- and left- eigenvectors associated with that have positive entries;
the multiplicity of the eigenvalue is one;
if B is row-stochastic, then r = 1, 1 is a simple eigenvalue with associated
right-eigenvector , and where is the
unique left-eigenvector corresponding to the eigenvalue 1 with positive entries
that sum to 1 (a stochastic vector).