Model 1 conjecture on the limiting pseudospectrum

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Let nn be the matrix size, let m≥1m\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 m≥1m\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 n→∞n\to\infty, and its interior becomes filled by eigenvalues of the perturbed system as n→∞n\to\infty. This predicts a nontrivial limiting pseudospectral region for model 1, although the supplied text gives no proof or resolution.

References

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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