T. Laffey

activity

20152020

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3 papers · 1 filter

math.SP2020

The Karpelevič Region Revisited

Stephen Kirkland, Thomas Laffey, Helena Smigoc

We consider the Karpelevič region $Θ_{n} \subset C$ consisting of all eigenvalues of all stochastic matrices of order $n$ . We provide an alternative characterisation of $Θ_n…

math.SP2019

The integer cp-rank of $2 \times 2$ matrices

Thomas Laffey, Helena Šmigoc

We show the cp-rank of an integer doubly nonnegative $2 \times 2$ matrix does not exceed $11$ .

math.SP2018

Diagonal realizability in the Nonnegative Inverse Eigenvalue Problem

Thomas J. Laffey, Helena Šmigoc

We show that if a list of nonzero complex numbers $σ = (λ_{1}, λ_{2}, \dots, λ_{k})$ is the nonzero spectrum of a diagonalizable nonnegative matrix, then $σ$ is the nonzero spectrum of a dia…

The Karpelevič Region Revisited

The integer cp-rank of 2×2 matrices

Diagonal realizability in the Nonnegative Inverse Eigenvalue Problem

The integer cp-rank of $2 \times 2$ matrices