Centers and isochronous centers for generalized quintic systems

Abstract

In this paper we classify the centers and the isochronous centers of certain polynomial differential systems in R2 of degree d≥5 odd that in complex notation are ż=(λ+i)z(zz̄)d−52(Az5+Bz4z̄+Cz3z̄2+Dz2z̄3+Ezz̄4+Fz̄5), where z=x+iy λ∈R and A,B,C,D,E,F∈C. Note that if d=5 we obtain the class of polynomial differential systems of the form a linear system with homogeneous polynomial nonlinearities of degree 5. Due to the huge computations required for computing the necessary and sufficient conditions for the characterization of the centers and isochronous centers, our study uses algorithms of computational algebra based on the Gröbner basis theory and on modular arithmetics.

The first author is partially supported by a MINECO/ FEDER grant number MTM2011-22877 and an AGAUR (Generalitat de Catalunya) grant number 2014SGR 1204. The second author is partially supported by a MINECO/ FEDER grant number MTM2008-03437, an AGAUR grant number 2014SGR 568, ICREA Academia, two FP7-PEOPLE-2012-IRSES numbers 316338 and 318999, and a FEDER/UNAB10-4E-378. The third author has been supported by FCT (grant PTDC/MAT/117106/2010 and through CAMGSD).