A. Gasull et al., THE PERIOD FUNCTION FOR HAMILTONIAN-SYSTEMS WITH HOMOGENEOUS NONLINEARITIES, Journal of differential equations, 139(2), 1997, pp. 237-260
The paper deals with Hamiltonian systems with homogeneous nonlineariti
es. We prove that such systems have no isochronous centers, that the p
eriod annulus of any of its centres is either bounded or the whole pla
ne and that the period function associated to the origin has at most o
ne critical point. (C) 1997 Academic Press.