|
Let X be a closed manifold with χ(X)=0, and let f:X→S1
be a circle-valued Morse function. We define an invariant I which
counts closed orbits of the gradient of f, together with flow lines
between the critical points. We show that our invariant equals a form of
topological Reidemeister torsion defined by Turaev [Math. Res. Lett. 4
(1997) 679–695].
We proved a similar result in our previous paper [Topology 38 (1999)
861–888], but the present paper refines this by separating closed orbits
and flow lines according to their homology classes. (Previously we
only considered their intersection numbers with a fixed level set.)
The proof here is independent of the previous proof, and also simpler.
Aside from its Morse-theoretic interest, this work is motivated by the
fact that when X is three-dimensional and b1(X)>0, the invariant
I equals a counting invariant I3(X) which was conjectured in our
previous paper to equal the Seiberg–Witten invariant of X. Our result,
together with this conjecture, implies that the Seiberg–Witten invariant
equals the Turaev torsion. This was conjectured by Turaev and refines
the theorem of Meng and Taubes [Math. Res. Lett 3 (1996)
661–674].
|