The Weinstein conjecture for periodic orbits on contact-type energy levels

Let (M,ω)(M,\omega) be a symplectic manifold and let H:MRH:M\to\mathbb{R} be a Hamiltonian. An energy level is a level set H1(c)H^{-1}(c), and a hypersurface YMY\subset M is of contact type if there is a contact form λ\lambda on YY such that ωY=dλ\omega|_Y=d\lambda. Weinstein conjecture. For any Hamiltonian on any symplectic manifold, the Hamiltonian flow has a periodic orbit on any compact energy level of contact type. This is equivalently phrased in terms of Reeb dynamics: every Reeb flow on a closed contact manifold should have a closed orbit. Important cases are known, including contact forms on S3S^3, three-manifolds with nonzero second homotopy, and overtwisted contact structures, but the general statement remains open.

Sources & referencesView supporting material

Primary source

Dan Cristofaro-Gardiner, “Low-dimensional topology and symplectic dynamics”, arXiv:2510.07680 (2025).

Additional references

13 papers in this index state this conjecture (1997–2025). The statement above is taken from the most recent of them; the others are arXiv:2508.01113, arXiv:2209.01467, arXiv:2103.09356, arXiv:1612.01009, arXiv:1104.0250, arXiv:1011.1690, arXiv:0906.2444, arXiv:0809.5088, arXiv:math/0601144, arXiv:math/9907112, arXiv:dg-ga/9708011, arXiv:dg-ga/9708006.

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