<?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>0034-7426</journal-id>
<journal-title><![CDATA[Revista Colombiana de Matemáticas]]></journal-title>
<abbrev-journal-title><![CDATA[Rev.colomb.mat.]]></abbrev-journal-title>
<issn>0034-7426</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional de Colombia y Sociedad Colombiana de Matemáticas]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0034-74262005000200005</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Symmetries and integration of differential equations]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Torres del Castillo]]></surname>
<given-names><![CDATA[Gerardo]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Marciano Melchor]]></surname>
<given-names><![CDATA[Magdalena]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Autónoma de Puebla Instituto de Ciencias Departamento de Física Matemática]]></institution>
<addr-line><![CDATA[Puebla ]]></addr-line>
<country>México</country>
</aff>
<aff id="A02">
<institution><![CDATA[,Universidad Autónoma de Puebla Facultad de Ciencias Físico Matemáticas ]]></institution>
<addr-line><![CDATA[Puebla ]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2005</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2005</year>
</pub-date>
<volume>39</volume>
<numero>2</numero>
<fpage>133</fpage>
<lpage>143</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_arttext&amp;pid=S0034-74262005000200005&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_abstract&amp;pid=S0034-74262005000200005&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_pdf&amp;pid=S0034-74262005000200005&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[A proof of the Lie theorem which relates the symmetries of a first order differential equation (or of a linear differential form) with its integrating factors is given. It is shown that a similar result partially applies for systems of linear differential forms and ordinary differential equations of any order.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Se da una prueba del teorema de Lie que relaciona las simetrías de una ecuación diferencial de primer orden(o de una forma diferencial lineal) con su factor integrante. Se demuestra que un resultado similar parcialmente aplica para sistemas de formas diferenciales lineales y ecuaciones diferenciales ordinarias de cualquier orden.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Ordinary differential equations]]></kwd>
<kwd lng="en"><![CDATA[symmetries]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[  <font size="2" face=verdana>      <p> <font size="4">       <center>   <b>Symmetries and integration of differential equations</b>   </center>  </font></p>     <p>&nbsp;</p>     <p><b>Gerardo Torres del Castillo<sup>1</sup> -</b> <b>Magdalena Marciano Melchor<sup>2</sup></b></p>      <p> <sup>1</sup>Departamento de F&iacute;sica Matem&aacute;tica. Instituto de Ciencias. Universidad    Aut&oacute;noma de Puebla. Apartado postal 1152. 72001 Puebla, M&eacute;xico.</p>     <p>e-mail: <a href="mailto:gtorres@fcfm.buap.mx">gtorres@fcfm.buap.mx</a></p>     <p><sup>2</sup>Facultad de Ciencias F&iacute;sico Matem&aacute;ticas. Universidad Aut&oacute;noma    de Puebla. Apartado postal 1152. 72001 Puebla, M&eacute;xico</p>     <p>e-mail: <a href="mailto:est068@fcfm.buap.mx">est068@fcfm.buap.mx</a></p> <hr>     <p><b>Abstract.</b> A proof of the Lie theorem which relates the symmetries of    a first order differential equation (or of a linear differential form) with    its integrating factors is given. It is shown that a similar result partially    applies for systems of linear differential forms and ordinary differential equations    of any order.</p>     ]]></body>
<body><![CDATA[<p><b><i>Keywords and phrases.</i></b> Ordinary differential equations, symmetries.</p>     <p><i>2000 Mathematics Subject Classification.</i> Primary: 34A26, 54H15. Secondary:    58D19, 35F05.</p> <hr size="1">     <p><b>Resumen.</b> Se da una prueba del teorema de Lie que relaciona las simetr&iacute;as    de una ecuaci&oacute;n diferencial de primer orden(o de una forma diferencial    lineal) con su factor integrante. Se demuestra que un resultado similar parcialmente    aplica para sistemas de formas diferenciales lineales y ecuaciones diferenciales    ordinarias de cualquier orden.</p> <hr>     <p>FULL TEXT IN <a href="pdf/rcm/v39n2/v39n2a05.pdf">PDF</a></p> <hr>     <p>    <center><b>References</b></center></p>     <!-- ref --><p> [1] G. F. Simmons, <i>Differential Equations. With Applications and Historical    Notes</i>, 2nd ed., 9. McGraw-Hill, New York, 1991.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000019&pid=S0034-7426200500020000500001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p> [2] N. H. Ibragimov, Sophus Lie and Harmony in Mathematical Physics, on the    150th Anniversary of His Birth, <i>The Mathematical Intelligencer</i> <b>16</b>,    20 (1994).&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000020&pid=S0034-7426200500020000500002&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p> [3] H. Stephani, <i>Differential Equations: Their Solution Using Symmetries</i>,    Cambridge University Press, Cambridge, 1989.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000021&pid=S0034-7426200500020000500003&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p> [4] L. Dresner, <i>Applications of Lie's Theory of Ordinary and Partial Differential    Equations</i>, Institute of Physics, Bristol, 1999.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000022&pid=S0034-7426200500020000500004&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p> [5] P. E. Hydon, <i>Symmetry Methods for Differential Equations: A Beginner's    Guide</i>, Cambridge University Press, Cambridge, 2000.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000023&pid=S0034-7426200500020000500005&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p> [6] C. von Westenholz, <i>Differential Forms in Mathematical Physics</i>,    North-Holland, Amsterdam, 1981.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000024&pid=S0034-7426200500020000500006&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><p>(Recibido en agosto de 2005. Aceptado en noviembre de 2005)</p>   </font>      ]]></body><back>
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