Winding-number conjecture for type II runaways under diagonal Toeplitz perturbations

Let TT be the Toeplitz matrix and let AjjA_{jj} denote the matrix with its (j,j)(j,j) entry selected. Consider the rank-one deformation

T(σ)=T+σAjj.T(\sigma)=T+\sigma A_{jj}.

Let the first-order perturbation correction be the corresponding collection of complex corrections, and let a Runaway type II be a runaway eigenvalue of this deformation. Winding-number conjecture. The number of Runaways type II in T(σ)T(\sigma) is equal to the winding number of the first-order perturbation correction about any point in the interior of the convex hull of the first-order corrections. This is an empirically observed relation for the rank-one deformation; the paper states that no proof is known and illustrates it numerically.

Sources & referencesView supporting material

Primary source

Ramis Movassagh and Leo P. Kadanoff, “Eigenpairs of Toeplitz and disordered Toeplitz matrices with a Fisher-Hartwig symbol”, arXiv:1604.08295 (2016).

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