4 citations · 4 across the 5 of their papers we have counts for
5 papers
Positive definite kernels and lattice paths
T. Constantinescu, Nermine El-Sissi
We discuss the structure of positive definite kernels in terms of operator models. In particular, we introduce two models, one of Hessenberg type and another one that we call near…
Orthogonal polynomials in several non-commuting variables. II
T. Banks, T. Constantinescu
In this paper we continue to investigate a certain class of Hankel-like positive definite kernels using their associated orthogonal polynomials. The main result of this paper is ab…
Tensor algebras and displacement structure. IV. Invariant kernels
T. Banks, T. Constantinescu, Nermine El-Sissi
In this paper we investigate the class of invariant positive definite kernels on the free semigroup on N generators. We provide a combinatorial description of the positivity of the…
Research problem: The completion number of a graph
M. Bakonyi, T. Constantinescu
Motivated by the remarkable interplay between (chordal) graphs and matrix algebra, we associate to each graph a so-called completion number that might encode some aspects of that i…
Relations on noncommutative variables and associated orthogonal polynomials
T. Banks, T. Constantinescu, J. L. Johnson
This semi-expository paper surveys results concerning three classes of orthogonal polynomials: in one non-hermitian variable, in several isometric non-commuting variables, and in s…