We develop techniques for defining and working with virtual fundamental cycles on
moduli spaces of pseudo-holomorphic curves which are not necessarily cut out
transversally. Such techniques have the potential for applications as foundations for
invariants in symplectic topology arising from “counting” pseudo-holomorphic
curves.
We introduce the notion of an
implicit atlas on a moduli space, which is (roughly)
a convenient system of local finite-dimensional reductions. We present a general
intrinsic strategy for constructing a canonical implicit atlas on any moduli space of
pseudo-holomorphic curves. The main technical step in applying this strategy in any
particular setting is to prove appropriate gluing theorems. We require only
topological gluing theorems, that is, smoothness of the transition maps between
gluing charts need not be addressed. Our approach to virtual fundamental cycles is
algebraic rather than geometric (in particular, we do not use perturbation).
Sheaf-theoretic tools play an important role in setting up our functorial algebraic
“VFC package”.
We illustrate the methods we introduce by giving definitions of
Gromov–Witten invariants and Hamiltonian Floer homology over
for general symplectic manifolds. Our framework generalizes to the
–equivariant setting,
and we use
–localization
to calculate Hamiltonian Floer homology. The Arnold conjecture (as treated by
Floer, by Hofer and Salamon, by Ono, by Liu and Tian, by Ruan, and by Fukaya and
Ono) is a well-known corollary of this calculation.
Keywords
virtual fundamental cycles, pseudo-holomorphic curves,
implicit atlases, Gromov–Witten invariants, Floer homology,
Hamiltonian Floer homology, Arnold conjecture,
$S^1$–localization, transversality, gluing