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Morse theory and asymptotic linear Hamiltonian system. (English) Zbl 0672.34037
We try to quote from the Introduction in order to give an idea on the paper avoiding technical details. “We consider the existence of 2π- periodic solutions of Hamiltonian systems -Jz ˙=H ' (z,t) (*)|H ' (s,t)-h s|/|s|0, as |s| |H ' (s,t)-h 0 s|/|s|0, as |s|0 (h ,h 0 are constant symmetric matrices and H ' denotes the gradient of H with respect to the first 2n variables). Given a constant 2n×2n matrix h we define an index i - (h). measuring the difference between the “sizes” of the negative spaces of the operators -Jd/dt-h and -Jd/dt. We define i 0 (h) which is just the dimension of the null space of -Jd/dt-h. Let H:R 2n ×RR be C 1 ,2π-periodic in t and satisfying (*). If i 0 (h 0 )=i 0 (h )=0 and i - (h 0 )i - (h ) then there exists at least one nontrivial periodic solution”. Morse theory and Galerkin method are combined.
Reviewer: A.Halanay

34C25Periodic solutions of ODE
70H05Hamilton’s equations