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

<record version="7" id="758">
 <title>singular</title>
 <name>Singular</name>
 <created>2001-11-12 02:30:40</created>
 <modified>2006-09-04 13:42:15</modified>
 <type>Definition</type>
 <creator id="13753" name="Mathprof"/>
 <author id="13753" name="Mathprof"/>
 <author id="2" name="akrowne"/>
 <classification>
	<category scheme="msc" code="15A12"/>
	<category scheme="msc" code="65F35"/>
 </classification>
 <synonyms>
	<synonym concept="singular" alias="non-invertible"/>
	<synonym concept="singular" alias="singular transformation"/>
 </synonyms>
 <preamble>\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{graphicx}
\usepackage{xypic}</preamble>
 <content>\section{Singular}


An $ m \times n$ matrix $ A$ with entries from a field is called \emph{singular} if its rows or columns are linearly dependent. This is equivalent to the following conditions:
\begin{enumerate}
\item
The nullity of $ A$ is greater than zero ( $ \operatorname{null}(A) &gt; 0$).
\item
The homogeneous linear system $ A\mathbf{x} = 0 $ has a non-trivial solution.
\end{enumerate}

If $m$ = $n$ this is equivalent to the following conditions:
\begin{enumerate}
\item
The determinant $ \det(A)=0$.
\item
The rank of $ A$ is less than $ n$.
\end{enumerate}
</content>
</record>
