<?xml version="1.0" encoding="UTF-8"?>

<record version="5" id="3482">
 <title>Toeplitz matrix</title>
 <name>ToeplitzMatrix</name>
 <created>2002-09-28 13:54:13</created>
 <modified>2005-08-14 13:05:28</modified>
 <type>Definition</type>
 <creator id="2" name="akrowne"/>
 <author id="2" name="akrowne"/>
 <classification>
	<category scheme="msc" code="65F35"/>
	<category scheme="msc" code="15A09"/>
	<category scheme="msc" code="15A57"/>
 </classification>
 <preamble>\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}

%\usepackage{psfrag}
%\usepackage{graphicx}
%\usepackage{xypic}</preamble>
 <content>\section{Toeplitz Matrix}

A \emph{Toeplitz matrix} is any $n\times n$ matrix with values constant along each (top-left to lower-right) diagonal.  That is, a Toeplitz matrix has the form

$$ \begin{bmatrix}
 a_0 &amp; a_1 &amp; a_2 &amp; \cdots &amp; a_{n-1} \\
 a_{-1} &amp; a_0 &amp; a_1 &amp; \ddots &amp; \vdots \\
 a_{-2} &amp; a_{-1} &amp; a_0 &amp; \ddots &amp; a_2 \\
 \vdots &amp; \ddots &amp; \ddots &amp; \ddots &amp; a_1 \\
 a_{-(n-1)} &amp; \cdots &amp; a_{-2} &amp; a_{-1} &amp; a_0
\end{bmatrix} $$

Numerical problems involving Toeplitz matrices typically have fast solutions (only $2n-1$ distinct elements need to be solved for, as opposed to $n^2$).  For example, the inverse of a symmetric, positive-definite $n\times n$ Toeplitz matrix can be found in $\mathcal{O}(n^2)$ \PMlinkname{time}{TimeComplexity}.

\begin{thebibliography}{3}
\bibitem{Golub} Golub and Van Loan, \emph{Matrix Computations}, Johns Hopkins University Press 1993
\end{thebibliography}</content>
</record>
