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<document xmlns="http://cnx.rice.edu/cnxml" xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="m11253">
  <name>The Gaussian Process</name>
  <metadata>
  <md:version>1.2</md:version>
  <md:created>2003/05/16</md:created>
  <md:revised>2003/08/04 17:18:04.228 GMT-5</md:revised>
  <md:authorlist>
    <md:author id="dhj">
      <md:firstname>Don</md:firstname>
      
      <md:surname>Johnson</md:surname>
      <md:email>dhj@rice.edu</md:email>
    </md:author>
  </md:authorlist>

  <md:maintainerlist>
    <md:maintainer id="dhj">
      <md:firstname>Don</md:firstname>
      
      <md:surname>Johnson</md:surname>
      <md:email>dhj@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="erkrause">
      <md:firstname>Eileen</md:firstname>
      
      <md:surname>Krause</md:surname>
      <md:email>erkrause@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="kclarks">
      <md:firstname>Kyle</md:firstname>
      
      <md:surname>Clarkson</md:surname>
      <md:email>kclarks@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="lizzardg">
      <md:firstname>Elizabeth</md:firstname>
      
      <md:surname>Gregory</md:surname>
      <md:email>lizzardg@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="kevinduh">
      <md:firstname>Kevin</md:firstname>
      
      <md:surname>Duh</md:surname>
      <md:email>kevinduh@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="mariyah">
      <md:firstname>Mariyah</md:firstname>
      
      <md:surname>Poonawala</md:surname>
      <md:email>mariyah@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="mjeanes">
      <md:firstname>Matthew</md:firstname>
      
      <md:surname>Jeanes</md:surname>
      <md:email>mjeanes@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer id="jsilv">
      <md:firstname>Jeffrey</md:firstname>
      
      <md:surname>Silverman</md:surname>
      <md:email>jsilv@rice.edu</md:email>
    </md:maintainer>
  </md:maintainerlist>
  
  

  <md:abstract/>
</metadata>

  <content>
    <para id="para1">
      A random process 
      <m:math>
	<m:apply>
	  <m:ci type="fn">X</m:ci>
	  <m:ci>t</m:ci>
	</m:apply>
      </m:math> is Gaussian if the joint density of the
      <m:math><m:ci>N</m:ci></m:math> amplitudes <m:math>
	<m:set>
	  <m:apply>
	    <m:ci type="fn">X</m:ci>
	    <m:ci><m:msub>
		<m:mi>t</m:mi>
		<m:mn>1</m:mn>
	      </m:msub></m:ci>
	  </m:apply>
	  <m:mo>…,</m:mo>
	  <m:apply>
	    <m:ci type="fn">X</m:ci>
	    <m:ci><m:msub>
		<m:mi>t</m:mi>
		<m:mi>N</m:mi>
	      </m:msub></m:ci>
	  </m:apply>
	</m:set>
      </m:math> comprise a Gaussian random vector.  The elements of
      the required covariance matrix equal the covariance between the
      appropriate amplitudes: <m:math>
	<m:apply>
	  <m:eq/>
	  <m:apply>
	    <m:selector/>
	    <m:ci type="matrix">K</m:ci>
	    <m:ci>i</m:ci>
	    <m:ci>j</m:ci>
	  </m:apply>
	  <m:apply>
	    <m:ci type="fn"><m:msub>
		<m:mi>K</m:mi>
		<m:mi>X</m:mi>
	      </m:msub></m:ci>
	    <m:ci><m:msub>
		<m:mi>t</m:mi>
		<m:mi>i</m:mi>
	      </m:msub></m:ci>
	    <m:ci><m:msub>
		<m:mi>t</m:mi>
		<m:mi>j</m:mi>
	      </m:msub></m:ci>
	  </m:apply>
	</m:apply>
      </m:math>.  Assuming the mean is known, the entire structure of
      the Gaussian random process is specified once the correlation
      function or, equivalently, the power spectrum is known.  As
      linear transformations of Gaussian random processes yield
      another Gaussian process, linear operations such as
      differentiation, integration, linear filtering, sampling, and
      summation with other Gaussian processes result in a Gaussian
      process.
    </para>   
  </content>
  
</document>
