The critical exponent conjecture for powers of doubly nonnegative matrices

Wielandt's proof of the exponent inequality for primitive nonnegative matrices

The proof of the exponent inequality found in Wielandt's unpublished diaries of a result announced without proof in his well known paper on nonnegative irreducible matrices. A facsimile, a transcription, a translation and a commentary are presented. © 2002 Published by Elsevier Science Inc. . In IDS famous paper [3] on nonnegative irreducible matrices published in 1950, Wielandt announced an in...

Separating doubly nonnegative and completely positive matrices

The cone of Completely Positive (CP) matrices can be used to exactly formulate a variety of NP-Hard optimization problems. A tractable relaxation for CP matrices is provided by the cone of Doubly Nonnegative (DNN) matrices; that is, matrices that are both positive semidefinite and componentwise nonnegative. A natural problem in the optimization setting is then to separate a given DNN but non-CP...

On A Conjecture Concerning Doubly Stochastic Matrices

In a 2002 paper, Kirkland showed that if T ∈ Rn×n is an irreducible stochastic matrix with stationary distribution vector πT , then for A = I − T , maxj=1,...,n πj‖A j ‖∞ ≥ n−1 n , where Aj , j = 1, . . . , n, are the (n − 1) × (n − 1) principal submatrices of A obtained by deleting the j–th row and column of A. He also conjectured that equality holds in that lower bound if and only if either T...

On a Conjecture concerning Doubly Stochastic Matrices

The Critical Exponent of Doubly Singular Parabolic Equations

In this paper we study the Cauchy problem of doubly singular parabolic equations ut = div ∇u σ ∇um + t x u with non-negative initial data. Here −1 < σ ≤ 0, m > max 0 1 − σ − σ + 2 /N satisfying 0 < σ +m ≤ 1, p > 1, and s ≥ 0. We prove that if θ > max − σ + 2 , 1 + s N 1 − σ − m − σ + 2 , then pc = σ +m + σ +m− 1 s + σ + 2 1+ s + θ /N > 1 is the critical exponent; i.e, if 1 < p ≤ pc then every n...