Non-contractibility conjecture for non-Hamiltonian subcircle actions

Let an mm-dimensional torus TT act symplectically on a 2n2n-dimensional closed connected symplectic manifold (M,ω)(M,\omega). Let 2r2r be the rank of the two-form ωT\omega_T from the paper's preceding result, and assume

mn+r1.m \ge n+r-1.

Non-contractibility conjecture. Then for every non-Hamiltonian subcircle action of TT, the orbits of the circle action and all of their iterates are non-contractible.

This is proposed as a natural generalization of the paper's complexity-one torsion result to symplectic torus actions with non-isotropic orbits. The source presents it as a belief rather than a result, and gives no resolution, so its status remains open.

Sources & referencesView supporting material

Primary source

Rei Henigman and Yael Karshon, “Symplectic torus actions with non-contractible orbits”, arXiv:2607.21159 (2026).

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