Toland, J. F. Existence of symmetric homoclinic orbits for systems of Euler-Lagrange equations. (English) Zbl 0589.34029 Nonlinear functional analysis and its applications, Proc. Summer Res. Inst., Berkeley/Calif. 1983, Proc. Symp. Pure Math. 45/2, 447-459 (1986). [For the entire collection see Zbl 0583.00018.] This paper gives the original version of some theorems in \({\mathbb{R}}^ 2\) which were subsequently generalised. The basic observation is that certain dynamical systems with indefinite Hamiltonian structure have orbits which are monotone in position space (not configuration or phase space), and that as a consequence the existence of homoclinic orbits can be inferred for the general theory [see H. Hofer and the author, Math. Ann. 268, 387-403 (1984; Zbl 0569.70017)]. Cited in 1 ReviewCited in 6 Documents MSC: 34C15 Nonlinear oscillations and coupled oscillators for ordinary differential equations 37-XX Dynamical systems and ergodic theory 34A34 Nonlinear ordinary differential equations and systems, general theory 34C28 Complex behavior and chaotic systems of ordinary differential equations Keywords:monotone trajectory; Hamiltonian structure; homoclinic orbits PDF BibTeX XML