<?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>S0034-74262010000100003</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[A Variational Characterization of the Fucik Spectrum and Applications]]></article-title>
<article-title xml:lang="es"><![CDATA[Una caracterización variacional del espectro de Fucik y aplicaciones]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[CASTRO]]></surname>
<given-names><![CDATA[ALFONSO]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[CHANG]]></surname>
<given-names><![CDATA[CHEN]]></given-names>
</name>
<xref ref-type="aff" rid="A02"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Harvey Mudd College  ]]></institution>
<addr-line><![CDATA[Claremont ]]></addr-line>
<country>USA</country>
</aff>
<aff id="A02">
<institution><![CDATA[,UTSA  ]]></institution>
<addr-line><![CDATA[San Antonio ]]></addr-line>
<country>USA</country>
</aff>
<pub-date pub-type="pub">
<day>15</day>
<month>06</month>
<year>2010</year>
</pub-date>
<pub-date pub-type="epub">
<day>15</day>
<month>06</month>
<year>2010</year>
</pub-date>
<volume>44</volume>
<numero>1</numero>
<fpage>23</fpage>
<lpage>40</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_arttext&amp;pid=S0034-74262010000100003&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_abstract&amp;pid=S0034-74262010000100003&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_pdf&amp;pid=S0034-74262010000100003&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[We characterize the \it Fucik spectrum (see [7]) of a class selfadjoint operators. Our characterization relies on Lyapunov-Schmidt reduction arguments. We use this characterization to establish the existence of solutions for a semilinear wave equation. This work has been motivated by the authors results in [4] where one dimensional second order ordinary differential equations are studied.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Se caracteriza el espectro de Fucik (véase [7]) de una clase de operadores autoadjuntos. Basamos esta caracterización en el método de reducción de Lyapunov-Schmidt. Usamos esta caracterización para demostrar la existencia de soluciones a una ecuación de onda semilineal. Este trabajo ha sido motivado por los resultados de los autores en [4] donde se estudian ecuaciones diferenciales ordinarias de segundo orden.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Fucik spectrum]]></kwd>
<kwd lng="en"><![CDATA[Saddle point principle]]></kwd>
<kwd lng="en"><![CDATA[Asymptotic behavior]]></kwd>
<kwd lng="es"><![CDATA[Espectro de Fucik]]></kwd>
<kwd lng="es"><![CDATA[principio de puntos de silla]]></kwd>
<kwd lng="es"><![CDATA[comportamiento asintótico]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ 
<font size="2" face="verdana">

    <p>
<b>
<font size="4">
    <center>
A Variational Characterization of the Fucik Spectrum and Applications
</center>
</font>
</b>
</p>

    <p>
<b>
<font size="3">
    <center>
Una caracterizaci&oacute;n  variacional del espectro de Fucik y aplicaciones
</center>
</font>
</b>
</p>

    <p>
    <center>
ALFONSO CASTRO<sup>1</sup>,
CHEN CHANG<sup>2</sup>
</center>
</p>

    <p>
<sup>1</sup>Harvey Mudd College, Claremont, USA. Email: <a href="mailto:castro@math.hmc.edu">castro@math.hmc.edu</a>
    <br>

<sup>2</sup>UTSA, San Antonio, USA. Email: <a href="mailto:chen.chang@utsa.edu">chen.chang@utsa.edu</a>
    <br>
</p>

<hr size="1">

    ]]></body>
<body><![CDATA[<p>
<b>
    <center>
Abstract
</center>
</b>
</p>

    <p>
We characterize the \it Fucik spectrum (see [7]) of a class selfadjoint operators. Our characterization relies on Lyapunov-Schmidt reduction arguments. We use this characterization to establish the existence of solutions for a semilinear wave equation. This work has been motivated by the authors results in [4] where one dimensional second order ordinary differential equations are studied.
</p>

    <p>
<b>
Key words:
</b>
Fucik spectrum,
Saddle point principle,
Asymptotic behavior.
</p>

<hr size="1">

<i>2000 Mathematics Subject Classification: 35J20, 35J25, 35J60.</i>

<hr size="1">

    <p>
<b>
    <center>
Resumen
</center>
</b>
</p>

    <p>
Se caracteriza el espectro de Fucik (v&eacute;ase [7]) de una clase de operadores autoadjuntos. Basamos esta caracterizaci&oacute;n en el m&eacute;todo de reducci&oacute;n de Lyapunov-Schmidt. Usamos esta caracterizaci&oacute;n para demostrar la existencia de soluciones a una ecuaci&oacute;n de onda semilineal. Este trabajo ha sido motivado por los resultados de los autores en [4] donde se estudian ecuaciones diferenciales ordinarias de segundo orden.
</p>

    <p>
<b>
Palabras clave:
</b>
Espectro de Fucik,
principio de puntos de silla,
comportamiento asint&oacute;tico.
</p>

<hr size="1">

    <p>
Texto completo disponible en <a href="pdf/rcm/v44n1/v44n1a03.pdf">PDF</a>
</p>

<hr size="1">

    <p>
<b>
<font size="3">
References
</font>
</b>
</p>


    ]]></body>
<body><![CDATA[<!-- ref --><p>
[1] A. K. Ben-Naoum, C. Fabry, and D. Smets, `Resonance with respect to the Fucik Spectrum´, <i>Electron. J. Differential Equations</i>, 37 (2000), 1-21.
&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=S0034-7426201000010000300001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[2] H. Brezis and L. Nirenberg, `Forced Vibrations for a Nonlinear Wave Equation´, <i>Comm. on Pure and Applied Mathematics</i> <i>31</i>,  (1978), 1-30.
&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=S0034-7426201000010000300002&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[3] A. Castro, `Hammerstein Integral Equations with Indefinite Kernel´, <i>Math. and Math. Sci.</i> <i>1</i>,  (1978), 187-201.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000025&pid=S0034-7426201000010000300003&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[4] A. Castro and C. Chang, `Asymptotic Behavior of the Potential and Existence of a Periodic Solution for a Second Order Differential Equation´, <i>Applicable Analysis</i> <i>82</i>, 11 (2003), 1029-1038.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000026&pid=S0034-7426201000010000300004&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[5] M. Cuesta and J. P. Gossez, `A Variational Approach to Nonresonance with Respect to the Fucik Spectrum´, <i>Nonlinear Analysis T.M.A.</i> <i>19</i>, 5 (1992), 487-500.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000027&pid=S0034-7426201000010000300005&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[6] M. Cuesta, D. G. de Figueiredo, and J. P. Gossez, `The Beginning of the Fucik Spectrum for the <i>p</i>-Laplacian´, <i>J. Differential Equations</i> <i>159</i>, 1 (1999), 212-238.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000028&pid=S0034-7426201000010000300006&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[7] S. Fucik, `Boundary Value Problems with Jumping Nonlinearities´, <i>Casopis Pest. Mat.</i> <i>101</i>,  (1976), 69-87.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000029&pid=S0034-7426201000010000300007&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[8] E. Massa, `On a Variational Characterization of a Part of the Fucik Spectrum and a Superlinear Equation for the Neumann <i>p</i>-Laplacian in Dimension One´, <i>Adv. Differential Equations</i> <i>9</i>, 5-6 (2004a), 699-720.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000030&pid=S0034-7426201000010000300008&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[9] E. Massa, `On a Variational Characterization of the Fucik Spectrum of the Laplacian and a Superlinear Sturm-Liouville Equation´, <i>Proc. Roy. Soc. Edinburgh Sect.</i> <i>A 134</i>, 3 (2004b), 557-577.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000031&pid=S0034-7426201000010000300009&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[10] E. Massa and B. Ruf, `On the Fucik Spectrum for Elliptic Systems´, <i>Topol. Methods Nonlinear Analysis</i> <i>27</i>, 2 (2006), 195-228.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000032&pid=S0034-7426201000010000300010&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[11] D. G. de Figueiredo and J. P. Gossez, `On the First Curve of the Fucik Spectrum of an Elliptic Operator´, <i>Differential and Integral Equations</i> <i>7</i>, 5-6 (1994), 1285-1302.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000033&pid=S0034-7426201000010000300011&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><!-- ref --><p>
[12] D. G. de Figueiredo and B. Ruf, `On the Periodic Fucik Spectrum and a Superlinear Sturm-Liouville Equation´, <i>Proc. Roy. Soc. Edinburgh Sect. A.</i> <i>123</i>, 1 (1993), 95-107.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=000034&pid=S0034-7426201000010000300012&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --><center>
<b>(Recibido en enero de 2009. Aceptado en abril de 2010)</b>
</center>
<hr size="1">

    <p>
Este art&iacute;culo se puede citar en <i>LaTeX</i> utilizando la siguiente referencia bibliogr&aacute;fica de <i>BibTeX</i>:
</p>
<code><font size="2" face="verdana">
@ARTICLE{RCMv44n1a03,    <br>
 &nbsp;&nbsp;&nbsp; AUTHOR &nbsp;= {Castro, Alfonso and Chang, Chen},    <br>
 &nbsp;&nbsp;&nbsp; TITLE &nbsp; = {{A Variational Characterization of the Fucik Spectrum and Applications}},    <br>
 &nbsp;&nbsp;&nbsp; JOURNAL = {Revista Colombiana de Matem&aacute;ticas},    <br>
&nbsp;&nbsp;&nbsp; YEAR &nbsp;&nbsp; = {2010},    <br>
&nbsp;&nbsp;&nbsp; volume &nbsp;= {44},    <br>
&nbsp;&nbsp;&nbsp; number &nbsp;= {1},    ]]></body>
<body><![CDATA[<br>
&nbsp;&nbsp;&nbsp; pages &nbsp; = {23-40}    <br>
}
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