Randomised twisted Toeplitz spectral-measure conjecture

Let a(x,z)a(x,z) be the symbol on [0,1]×T[0,1]\times\mathbb{T}

a(x,z)=j=qpaj(x)zj,a(x,z)=\sum_{j=-q}^p a_j(x)z^j,

where aj(x)a_j(x) are continuous complex-valued functions on [0,1][0,1]. Let Tn(a)\mathcal{T}_n(a) be the randomised twisted Toeplitz matrix defined in the source, and let νx\nu_x be the weak limit of the eigenvalue-counting measures of the frozen Toeplitz matrices associated with ax=a(x,)a_x=a(x,\cdot). Define

μn=1nλsp(Tn(a))δλ.\mu_n=\frac{1}{n}\sum_{\lambda\in\operatorname{sp}(\mathcal{T}_n(a))}\delta_\lambda.

Randomised twisted Toeplitz spectral-measure conjecture. The measures μn\mu_n converge weakly to

μ=01νxdx.\mu=\int_0^1\nu_x\,dx.

This conjecture predicts the same averaged frozen-symbol limit for random sampling points in the symbol as for structured banded perturbations. The supplied source does not state whether the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Dario Giandinoto and Boris Shapiro, “Structured perturbations of tridiagonal twisted Toeplitz matrices”, arXiv:2604.20617 (2026).

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