<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/xsl" href="static/style.xsl"?><OAI-PMH xmlns="http://www.openarchives.org/OAI/2.0/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/ http://www.openarchives.org/OAI/2.0/OAI-PMH.xsd"><responseDate>2026-04-17T02:19:45Z</responseDate><request verb="GetRecord" identifier="oai:www.recercat.cat:2072/458056" metadataPrefix="marc">https://recercat.cat/oai/request</request><GetRecord><record><header><identifier>oai:recercat.cat:2072/458056</identifier><datestamp>2025-02-25T12:50:21Z</datestamp><setSpec>com_2072_98</setSpec><setSpec>col_2072_378192</setSpec></header><metadata><record xmlns="http://www.loc.gov/MARC21/slim" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:doc="http://www.lyncode.com/xoai" xsi:schemaLocation="http://www.loc.gov/MARC21/slim http://www.loc.gov/standards/marcxml/schema/MARC21slim.xsd">
   <leader>00925njm 22002777a 4500</leader>
   <datafield ind2=" " ind1=" " tag="042">
      <subfield code="a">dc</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Itikawa, Jackson</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Oliveira, Regilene</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="720">
      <subfield code="a">Torregrosa, Joan</subfield>
      <subfield code="e">author</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="260">
      <subfield code="c">2022</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="520">
      <subfield code="a">Altres ajuts: acords transformatius de la UAB</subfield>
   </datafield>
   <datafield ind2=" " ind1=" " tag="520">
      <subfield code="a">In the weak 16th Hilbert problem, the Poincaré-Pontryagin-Melnikov function, M(h), is used for obtaining isolated periodic orbits bifurcating from centers up to a first-order analysis. This problem becomes more difficult when a family of centers is considered. In this work we provide a compact expression for the first-order Taylor series of the function M(h,a) with respect to a, being a the multi-parameter in the unperturbed center family. More concretely, when the center family has an explicit first integral or inverse integrating factor depending on a. We use this new bifurcation mechanism to increase the number of limit cycles appearing up to a first-order analysis without the difficulties that higher-order studies present. We show its effectiveness by applying it to some classical examples.</subfield>
   </datafield>
   <datafield tag="653" ind2=" " ind1=" ">
      <subfield code="a">Limit cycle</subfield>
   </datafield>
   <datafield tag="653" ind2=" " ind1=" ">
      <subfield code="a">Melnikov functions</subfield>
   </datafield>
   <datafield tag="653" ind2=" " ind1=" ">
      <subfield code="a">Averaging theory</subfield>
   </datafield>
   <datafield tag="653" ind2=" " ind1=" ">
      <subfield code="a">Multi-parameter perturbation</subfield>
   </datafield>
   <datafield ind2="0" ind1="0" tag="245">
      <subfield code="a">First-order perturbation for multi-parameter center families</subfield>
   </datafield>
</record></metadata></record></GetRecord></OAI-PMH>