<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0035-001X</journal-id>
<journal-title><![CDATA[Revista mexicana de física]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. mex. fis.]]></abbrev-journal-title>
<issn>0035-001X</issn>
<publisher>
<publisher-name><![CDATA[Sociedad Mexicana de Física]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0035-001X2008000900015</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Alternative method for determining the Feynman propagator of a relativistic quantum mechanical problem]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Moshinsky]]></surname>
<given-names><![CDATA[M]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Sadurní]]></surname>
<given-names><![CDATA[E]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Física ]]></institution>
<addr-line><![CDATA[México D.F]]></addr-line>
<country>México</country>
</aff>
<aff id="A02">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Ciencias Físicas ]]></institution>
<addr-line><![CDATA[Cuernavaca Morelos]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2008</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2008</year>
</pub-date>
<volume>54</volume>
<fpage>92</fpage>
<lpage>98</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0035-001X2008000900015&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0035-001X2008000900015&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0035-001X2008000900015&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[The authors, together with A. del Campo, developed an alternative method for determining the Feynman propagator [1] for a non-relativistic problem. One started with the time dependent Schroedinger equation for the problem. Carried out a Laplace transform with respect to time to get the equation for the energy dependent Green function and derived it explicitly. We then carried out the inverse Laplace transform in the energy to get Feynman propagator. In this paper we carry out the same programme for a relativistic problem associated with the one dimensional Dirac equation of a free particle and the Dirac oscillator proposed by Moshinsky and Szczepaniak [2] twenty years ago.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Los autores desarrollaron, junto con A. del Campo, un método alternativo para determinar el propagador de Feynman para un problema norelativista. El método consiste en la evaluación de la transformada de Laplace con respecto al tiempo para derivar la ecuación para la función de Green dependiente de energía. Se obtiene el propagador de Feynman usando la transformada inversa de Laplace de la función de Green. En este artículo llevamos a cabo el mismo programa para un problema relativista asociado a la ecuación de Dirac en una dimensión de una partícula libre y el oscilador de Dirac propuesto hace veinte anos por Moshinsky and Szczepaniak [2].]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Feynman propagator]]></kwd>
<kwd lng="en"><![CDATA[Dirac oscillator]]></kwd>
<kwd lng="en"><![CDATA[relativistic Green functions]]></kwd>
<kwd lng="es"><![CDATA[Propagador de Feynman]]></kwd>
<kwd lng="es"><![CDATA[oscilador de Dirac]]></kwd>
<kwd lng="es"><![CDATA[funciones de Green relativistas]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <p align="center"><font face="verdana" size="4"><b>Alternative method for determining the Feynman propagator of a relativistic quantum mechanical problem</b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="2"><b>M. Moshinsky<sup>a,</sup><a href="#nota">*</a> and E. Sadurn&iacute;<sup> b</sup></b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><i>&ordf; Instituto de F&iacute;sica, Universidad Nacional Aut&oacute;noma de M&eacute;xico, Apartado Postal 20&#150;364, M&eacute;xico, D.F. 01000 M&eacute;xico, </i>e&#150;mail:<a href="mailto:moshi@fisica.unam.mx">moshi@fisica.unam.mx</a></font></p>     <p align="justify"><font face="verdana" size="2"><i><sup>b</sup> Instituto de Ciencias F&iacute;sicas, Universidad Nacional Aut&oacute;noma de M&eacute;xico, 62210 Cuernavaca, Morelos, M&eacute;xico, </i>e&#150;mail:<a href="mailto:sadurni@fis.unam.mx">sadurni@fis.unam.mx</a></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">Recibido el 8 de febrero de 2008    <br> Aceptado el 15 de julio de 2008</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2"><b>Abstract</b></font></p>     <p align="justify"><font face="verdana" size="2">The authors, together with A. del Campo, developed an alternative method for determining the Feynman propagator &#91;1&#93; for a non&#150;relativistic problem. One started with the time dependent Schroedinger equation for the problem. Carried out a Laplace transform with respect to time to get the equation for the energy dependent Green function and derived it explicitly. We then carried out the inverse Laplace transform in the energy to get Feynman propagator. In this paper we carry out the same programme for a relativistic problem associated with the one dimensional Dirac equation of a free particle and the Dirac oscillator proposed by Moshinsky and Szczepaniak &#91;2&#93; twenty years ago.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Keywords: </b>Feynman propagator; Dirac oscillator; relativistic Green functions.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Resumen</b></font></p>     <p align="justify"><font face="verdana" size="2">Los autores desarrollaron, junto con A. del Campo, un m&eacute;todo alternativo para determinar el propagador de Feynman para un problema norelativista. El m&eacute;todo consiste en la evaluaci&oacute;n de la transformada de Laplace con respecto al tiempo para derivar la ecuaci&oacute;n para la funci&oacute;n de Green dependiente de energ&iacute;a. Se obtiene el propagador de Feynman usando la transformada inversa de Laplace de la funci&oacute;n de Green. En este art&iacute;culo llevamos a cabo el mismo programa para un problema relativista asociado a la ecuaci&oacute;n de Dirac en una dimensi&oacute;n de una part&iacute;cula libre y el oscilador de Dirac propuesto hace veinte anos por Moshinsky and Szczepaniak &#91;2&#93;.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Descriptores: </b>Propagador de Feynman; oscilador de Dirac; funciones de Green relativistas. </font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">PACS: 03.65.&#150;w; 03.65.Pm; 03.65.Ge</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2"><a href="/pdf/rmf/v54s3/v54s3a15.pdf" target="_blank">DESCARGAR ART&Iacute;CULO EN FORMATO PDF</a></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>References</b></font></p>     <!-- ref --><p align="justify"><font face="verdana" size="2">1. M. Moshinsky, E. Sadurn&iacute; and A. del Campo, <i>Alternative method for  determining the Feynman propagator  of non&#150;relativistic quantum mechanical problem </i>SIGMA <b>3</b> (2007) 110.</font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=8350960&pid=S0035-001X200800090001500001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p align="justify"><font face="verdana" size="2">2. M. Moshinsky and A. Szczepaniak, <i>J. Phys. A: Math Gen. </i><b>22</b> (199) L817.</font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=8350961&pid=S0035-001X200800090001500002&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p align="justify"><font face="verdana" size="2">3. Feynman and Hibbs. Quantum Mechanics and Path Integrals, McGraw Hill 1965.</font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=8350962&pid=S0035-001X200800090001500003&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p align="justify"><font face="verdana" size="2">4. J.C. 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Ando, <i>Phys Rev B, </i><b>65</b> (2002) 235412&#150;1.</font>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=8350973&pid=S0035-001X200800090001500014&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b><a name="nota"></a>Note</b></font></p>     <p align="justify"><font face="verdana" size="2">* Member of El Colegio Nacional and Sistema Nacional de Investigadores.</font></p>     ]]></body>
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