UAB Digital Repository of Documents 3 records found  Search took 0.00 seconds. 
1.
7 p, 135.0 KB Polynomial systems : a lower bound for the weakened 16th Hilbert problem / Li, Chengzhi (Peking University. Department of Mathematics) ; Li, Weigu (Peking University. Department of Mathematics) ; Llibre, Jaume (Universitat Autònoma de Barcelona. Departament de Matemàtiques) ; Zhang, Zhifen (Peking University. Department of Mathematics)
In this paper we provide the greatest lower bound about the number of (non-infinitesimal) limit cycles surrounding a unique singular point for a planar polynomial differential system of arbitrary degree.
2001
Extracta mathematicae, Vol. 16, Núm. 3 (2001) , p. 441-447  
2.
12 p, 107.2 KB Abelian integrals of quadratic hamiltonian vector fields with an invariant straight line / Li, Chengzhi (Beijing University. Department of Mathematics) ; Llibre, Jaume (Universitat Autònoma de Barcelona. Departament de Matemàtiques) ; Zhang, Zhifen (Beijing University. Department of Mathematics)
We prove that the lowest upper bound for the number of isolated zeros of the Abelian integrals associated to quadratic Hamiltonian vector fields having a center and an invariant straight line after quadratic perturbations is one.
1995 - 10.5565/PUBLMAT_39295_11
Publicacions matemàtiques, Vol. 39, Núm. 2 (1995) , p. 355-366  
3.
31 p, 235.2 KB Bifurcations of limit cycles from cubic Hamiltonian systems with a center and a homoclinic saddle-loop / Zhao, Yulin ; Zhang, Zhifen
It is provedin this paper that the maximum number of limit cycles of system [formula] is equal to two in the finite plane, where [formula]. This is partial answer to the seventh question in [2], posed by Arnold.
2000 - 10.5565/PUBLMAT_44100_08
Publicacions matemàtiques, V. 44 N. 1 (2000) , p. 205-235  

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