We give a generalization of the concept of near-symplectic structures to
dimensions. According to our definition, a closed
–form on a
–manifold
is near-symplectic if it is symplectic outside a submanifold
of
codimension
where
vanishes. We depict how this notion relates to near-symplectic
–manifolds
and broken Lefschetz fibrations via some examples. We define a generalized
broken Lefschetz fibration as a singular map with indefinite folds and
Lefschetz-type singularities. We show that, given such a map on a
–manifold over a symplectic
base of codimension
,
the total space carries such a near-symplectic structure whose singular locus corresponds
precisely to the singularity set of the fibration. A second part studies the geometry around the
codimension-
singular locus
.
We describe a splitting property of the normal bundle
that
is also present in dimension four. A tubular neighbourhood theorem for
is
provided, which has a Darboux-type theorem for near-symplectic forms as a
corollary.
Department of Mathematics
The Pennsylvania State University
University Park
State College, PA 16802
United States
Department of Mathematical Sciences
Durham University
Science Laboratories
South Rd
Durham DH1 3LE United Kingdom