Model 1 conjecture on the limiting pseudospectrum

Let nn be the matrix size, let m1m\geq 1 be fixed, and let SδJ(1)(m)S_{\delta J}^{(1)}(m) denote model 1. Let λ0\lambda_0 be the distinguished point included in the pseudospectrum, and let fS^m(T)=Tf_{\widehat{S}^m}(\mathbb{T})=\mathbb{T} be the unit-circle symbol curve. Model 1 pseudospectrum conjecture. At each fixed m1m\geq 1, the boundary of the pseudospectrum containing λ0\lambda_0 increases in size as nn increases, converges to the unit circle T=fS^m(T)\mathbb{T}=f_{\widehat{S}^m}(\mathbb{T}) as nn\to\infty, and its interior becomes filled by eigenvalues of the perturbed system as nn\to\infty. This predicts a nontrivial limiting pseudospectral region for model 1, although the supplied text gives no proof or resolution.

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Primary source

Saori Morimoto, Makoto Katori and Tomoyuki Shirai, “Eigenvalue and pseudospectrum processes generated by nonnormal Toeplitz matrices with rank 1 perturbations”, arXiv:2401.08129 (2025).

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