The spectrum of the perturbed shift operator $T: f(n)to al f(n+1)+a(n)f(n)$ in $l^2(Z)$ is considered for periodic $a(n)$ and fixed constant $al>0$. It is proven that the spectrum is continuous and fills a lemniscate. Some isospectral deformations of the sequence $a(n)$ are described. Similar facts for the perturbed shift in the spaces of sequences of some hypercomplex numbers is derived. |
Keywords
Shift Operator, Spectrum, lemniscate
Math Review Classification
Last Updated
Length
11 pages
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