Hilbert numbers for low degree systems

2020-01-21 16:15-17:15 Room 1303, Sciences Building No. 1

Abstract: We will present the best lower bounds, that are known up to now, for the  Hilbert numbers of polynomial vector fields of degree N, H(N), for small values of N. These limit cycles appear bifurcating from symmetric Darboux reversible centers with high simultaneous cyclicity. The considered systems have, at least, three centers, one on the  reversibility straight line and two symmetric about it. More concretely, the limit cycles are in a three nests configuration and the total number of limit cycles is at least 2n+m, for some values of n and m. The new lower bounds are obtained using simultaneous degenerate Hopf bifurcations. In particular, H(4) ≥ 28, H(5) ≥ 37, H(6) ≥ 53, H(7) ≥ 74, H(8) ≥ 96, H(9) ≥ 120, and H(10) ≥ 142.

This is a joint work with Rafel Prohens (UIB)