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<field name="value">Bravo, José Luis</field>
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<field name="value">Fernández, Manuel</field>
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<field name="value">Ojeda, Ignacio</field>
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<field name="value">This article deals with the study of the number of limit&#xd;
cycles surrounding a critical point of a quadratic planar vector field,&#xd;
which, in normal form, can be written as x&#xd;
′ = a1x − y − a3x&#xd;
2 + (2a2 +&#xd;
a5)xy+a6y&#xd;
2&#xd;
, y&#xd;
′ = x+a1y+a2x&#xd;
2+(2a3+a4)xy−a2y&#xd;
2&#xd;
. In particular, we&#xd;
study the semi-varieties defined in terms of the parameters a1, a2, . . . , a6&#xd;
where some classical criteria for the associated Abel equation apply.&#xd;
The proofs will combine classical ideas with tools from computational&#xd;
algebraic geometry.</field>
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<field name="value">Agencia Estatal de Investigación - Fondo Europeo de Desarrollo Regional (grant MTM 2011-22751)</field>
<field name="value">Junta de Extremadura (grant GR15055)</field>
<field name="value">Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional  (grant MTM2015-65764-C3-1-P)</field>
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<field name="value">Solución en forma cerrada</field>
<field name="value">Periodic solution</field>
<field name="value">Solución periódica</field>
<field name="value">Limit cycles</field>
<field name="value">Ciclos límite</field>
</element>
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<element name="title">
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<field name="value">Uniqueness of limit cycles for quadratic vector fields</field>
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