Volume 12, Issue 3
Spectral Distribution in the Eigenvalues Sequence of Products of g-Toeplitz Structures

Eric Ngondiep

10.4208/nmtma.OA-2017-0127

Numer. Math. Theor. Meth. Appl., 12 (2019), pp. 750-777.

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  • Abstract

Starting from the definition of an $n\times n$ $g$-Toeplitz matrix, $\!T_{n,g}\!\!\left(\!u\!\right)\!=\!\left[\!\widehat{u}_{r-gs}\!\right]_{\!r,s=0}^{n-1}\!,$ where $g$ is a given nonnegative parameter, $\{\widehat{u}_{k}\}$ is the sequence of Fourier coefficients of the Lebesgue integrable function $u$ defined over the domain $\mathbb{T}=(-\pi,\pi]$, we consider the product of $g$-Toeplitz sequences of matrices $\{T_{n,g}(f_{1})T_{n,g}(f_{2})\},$ which extends the product of Toeplitz structures $\{T_{n}(f_{1})T_{n}(f_{2})\},$ in the case where the symbols $f_{1},f_{2}\in L^{\infty}(\mathbb{T}).$ Under suitable assumptions, the spectral distribution in the eigenvalues sequence is completely characterized for the products of $g$-Toeplitz structures. Specifically, for $g\geq2$ our result shows that the sequences $\{T_{n,g}(f_{1})T_{n,g}(f_{2})\}$ are clustered to zero. This extends the well-known result, which concerns the classical case (that is, $g=1$) of products of Toeplitz matrices. Finally, a large set of numerical examples confirming the theoretic analysis is presented and discussed.

  • History

Published online: 2019-04

  • AMS Subject Headings

65F10, 15A18, 47B36, 47B65

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