Norm estimates of discrete Schrödinger operators
Colloquium Mathematicum, Tome 76 (1998) no. 1, pp. 153-160
Harper's operator is defined on $\ell^2({\sym Z})$ by $$ H_\theta \xi(n) = \xi(n+1) + \xi(n-1) + 2\cos n\theta\, \xi(n), $$ where $\theta\! \in \![0,\pi]$. We show that the norm of $\|H_\theta\|$ is less than or equal to $2\sqrt{2}$ for $\pi/2 \le\theta\le \pi$. This solves a conjecture stated in [1]. A general formula for estimating the norm of self-adjoint tridiagonal infinite matrices is also derived.
@article{10_4064_cm_76_1_153_160,
author = {Ryszard Szwarc},
title = {Norm estimates of discrete {Schr\"odinger} operators},
journal = {Colloquium Mathematicum},
pages = {153--160},
year = {1998},
volume = {76},
number = {1},
doi = {10.4064/cm-76-1-153-160},
language = {en},
url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-76-1-153-160/}
}
Ryszard Szwarc. Norm estimates of discrete Schrödinger operators. Colloquium Mathematicum, Tome 76 (1998) no. 1, pp. 153-160. doi: 10.4064/cm-76-1-153-160
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