Wilhelmus of Positivity

Positivity and Conditional Positivity of Loewner Matrices

We give elementary proofs of the fact that the Loewner matrices [ f(pi)−f(pj) pi−pj ] corresponding to the function f(t) = t on (0,∞) are positive semidefinite, conditionally negative definite, and conditionally positive definite, for r in [0, 1], [1, 2], and [2, 3], respectively. We show that in contrast to the interval (0,∞) the Loewner matrices corresponding to an operator convex function on...

Positivity And

We prove Okounkov’s conjecture, a conjecture of Fomin-FultonLi-Poon, and a special case of Lascoux-Leclerc-Thibon’s conjecture on Schur positivity and give several more general statements using a recent result of Rhoades and Skandera. An alternative proof of this result is provided. We also give an intriguing log-concavity property of Schur functions. 1. Schur positivity conjectures The ring of...

Domains of Positivity

A Domain of Positivity D is an open convex cone associated with a nonsingular symmetric matrix S, called the characteristic, such that xÇzD if and only if x'Sy>0 for all y(~D* As such they were introduced by Koecher (1) in generalization of the cone of positive definite matrices studied by Siegel. The automorphisms of D are the nonsingular linear transformations mapping D onto itself. The group...

Positivity Of Trigonometri Polynomials

Positivity of Mixed Multiplicities

Let R = ⊕(u,v)∈N2R(u,v) be a standard bigraded algebra over an artinian local ring K = R(0,0). Standard means R is generated over K by a finite number of elements of degree (1, 0) and (0, 1). Since the length l(R(u,v)) of R(u,v) is finite, we can consider l(R(u,v)) as a function in two variables u and v. This function was first studied by van der Waerden [W] and Bhattacharya [B] who proved that...