Using the mirror theorem [15], we give a Landau-Ginzburg mirror description for the big equivariant quantum cohomology of toric Deligne-Mumford stacks. More precisely, we prove that the big equivariant quantum D-module of a toric Deligne-Mumford stack is isomorphic to the Saito structure associated to the mirror Landau-Ginzburg potential. We give a GKZ-style presentation of the quantum D-module, and a combinatorial description of quantum cohomology as a quantum Stanley-Reisner ring. We establish the convergence of the mirror isomorphism and of quantum cohomology in the big and equivariant setting. TOM COATES, ALESSIO CORTI, HIROSHI IRITANI, AND HSIAN-HUA TSENG 7.1. Result 47 7.2. Estimates for the Gauss-Manin connection 49 7.3. Gauge fixing 51 7.4. Proof of Theorem 7.2 and Corollary 7.3 55 References 55
IntroductionThis paper is the last in a series of papers [14, 15] that study the genus-zero Gromov-Witten theory of toric Deligne-Mumford stacks. Let X be a toric Deligne-Mumford stack, or toric stack for short, that satisfies a mild semi-projectivity hypothesis (spelled out below). In [15] we proved a mirror theorem that says that a certain hypergeometric function, called the I-function, lies on the Givental cone for X. This determines all genus-zero Gromov-Witten invariants of X. The present paper builds on this mirror theorem to establish Hodgetheoretic mirror symmetry for toric stacks in a very general setting -without assuming that X is compact, or imposing any positivity condition on c 1 (X). We prove that the big and equivariant quantum cohomology D-module of X can be described as the Saito structure of the Landau-Ginzburg model mirror to X.It has been proposed by Givental [32] (see also [46]) that the mirror of a toric manifold X is a Landau-Ginzburg model, or more precisely, a Laurent polynomial function F = F (x 1 , . . . , x n ) with Newton polytope equal to the fan polytope of X. In particular, Givental [37] showed that, for weak Fano toric manifolds X, oscillatory integrals e F/z dx 1 ···dxnx 1 ···xn give solutions of the small quantum cohomology D-module of X. His result also implies that the quantum cohomology ring of X is isomorphic to the Jacobian ring of F , via an isomorphism which matches the Poincaré pairing with the residue pairing. Givental-style mirror symmetry has been extended to big quantum cohomology by Barannikov, and Mann [3,27,60]; this compares the Frobenius manifold structure [28] defined by the big quantum cohomology of X with K. Saito's flat structure [71, 72] associated to a miniversal unfolding of F .Let us briefly review our main construction. Let X be a toric Deligne-Mumford stack with semi-projective coarse moduli space. (This means that the coarse moduli space is projective over affine and contains a torus-fixed point.) We introduce an unfolding F (x; y) of Givental's Landau-Ginzburg potential by choosing a finite subset G in the fan lattice N:where b 1 , . . . , b m are generators of one-dimensional cones of the stacky fan of X, Q is the Novikov variable, λ(b i ) and λ...