In differential geometry, an almost symplectic structure on a differentiable manifold
is a two-form
on
that is everywhere non-singular.[1] If in addition
is closed then it is a symplectic form.
An almost symplectic manifold is an Sp-structure; requiring
to be closed is an integrability condition.
References
Further reading
Alekseevskii, D.V. (2001) [1994], "Almost-symplectic structure", Encyclopedia of Mathematics, EMS Press