<?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>S0035-001X2012000200003</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Higher dimensional gravity and Farkas property in oriented matroid theory]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Nieto]]></surname>
<given-names><![CDATA[J.A.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[León]]></surname>
<given-names><![CDATA[E.A.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad Autónoma de Sinaloa Facultad de Ciencias Físico-Matemáticas ]]></institution>
<addr-line><![CDATA[Culiacán Sinaloa]]></addr-line>
<country>México</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>04</month>
<year>2012</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>04</month>
<year>2012</year>
</pub-date>
<volume>58</volume>
<numero>2</numero>
<fpage>133</fpage>
<lpage>138</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0035-001X2012000200003&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0035-001X2012000200003&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0035-001X2012000200003&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[We assume gravity in a d-dimensional manifold M and consider a splitting of the form M = Mp × Mq, with d = p + q. The most general two-block metric associated with Mp and Mq is used to derive the corresponding Einstein-Hilbert action S. We focus on the special case of two distinct conformal factors &#968; and &#966; (&#968; for the metric in Mp and &#966; for the metric in Mq), and we write the action S in the form S = Sp+Sq, where Sp and Sq are actions associated with Mp and Mq, respectively. We show that a simplified action is obtained precisely when ip = p-1. In this case, we find that under the duality transformation &#966; &#8596; &#966;-1, the action Sp for the Mp-space or the action Sq for the Mq-space remain invariant, but not both. This result establishes an analogy between Farkas property in oriented matroid theory and duality in general relativity. Furthermore, we argue that our approach can be used in several physical scenarios such as 2t physics and cosmology.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Higher dimensional gravity]]></kwd>
<kwd lng="en"><![CDATA[gravitational duality]]></kwd>
<kwd lng="en"><![CDATA[2t physics]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <p align="justify"><font face="verdana" size="4">Investigaci&oacute;n</font></p>     <p align="justify"><font face="verdana" size="4">&nbsp;</font></p>     <p align="center"><font face="verdana" size="4"><b>Higher dimensional gravity and Farkas property in oriented matroid theory</b></font></p>     <p align="center"><font face="verdana" size="2">&nbsp;</font></p>     <p align="center"><font face="verdana" size="2"><b>J.A. Nieto and E.A. Le&oacute;n</b></font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><i>Facultad de Ciencias F&iacute;sico&#150;Matem&aacute;ticas de la Universidad Aut&oacute;noma de Sinaloa, 80010, Culiac&aacute;n Sinaloa, M&eacute;xico, e&#150;mails: </i><a href="mailto:nieto@uas.uasnet.mx">nieto@uas.uasnet.mx</a>; <a href="mailto:ealeon@uas.edu.mx">ealeon@uas.edu.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 17 de octubre de 2011.    <br> Aceptado el 16 de febrero de 2012.</font></p>     ]]></body>
<body><![CDATA[<p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><b>Abstract</b></font></p>     <p align="justify"><font face="verdana" size="2">We assume gravity in a <i>d</i>&#150;dimensional manifold <i>M </i>and consider a splitting of the form <i>M = M<sub>p</sub> </i>&times;<i> M<sub>q</sub></i>, with <i>d = p </i>+ <i>q</i>. The most general two&#150;block metric associated with <i>M<sub>p</sub> </i>and <i>M<sub>q</sub> </i>is used to derive the corresponding Einstein&#150;Hilbert action <i>S</i>. We focus on the special case of two distinct conformal factors <i> &#968;</i> and <i>&#966; </i>(<i>&#968;</i> for the metric in <i>M<sub>p</sub> </i>and <i>&#966;</i> for the metric in <i>M<sub>q</sub></i>), and we write the action <i>S </i>in the form <i>S = S<sub>p</sub>+S<sub>q</sub></i>, where <i>S<sub>p</sub> </i>and <i>S<sub>q</sub> </i>are actions associated with <i>M<sub>p</sub> </i>and <i>M<sub>q</sub></i>, respectively. We show that a simplified action is obtained precisely when <i>ip = p<sup>&#150;1</sup></i>. In this case, we find that under the duality transformation <i>&#966;</i> &#8596;<i> &#966;</i><sup>&#150;1</sup>, the action <i>S<sub>p</sub> </i>for the M<sub>p</sub>&#150;space or the action <i>S<sub>q</sub> </i>for the <i>M<sub>q</sub></i>&#150;space remain invariant, but not both. This result establishes an analogy between Farkas property in oriented matroid theory and duality in general relativity. Furthermore, we argue that our approach can be used in several physical scenarios such as 2t physics and cosmology.</font></p>     <p align="justify"><font face="verdana" size="2"><b>Keywords: </b>Higher dimensional gravity; gravitational duality; 2t physics.</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2">PACS: 04.60.&#150;m; 04.65.+e; 11.15.&#150;q; 11.30.Ly</font></p>     <p align="justify"><font face="verdana" size="2">&nbsp;</font></p>     <p align="justify"><font face="verdana" size="2"><a href="/pdf/rmf/v58n2/v58n2a3.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>     ]]></body>
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