Morrison, DR; Plesser, M, *Summing the instantons: Quantum cohomology and mirror symmetry in toric varieties*,
Nuclear Physics B, vol. 440 no. 1-2
(April, 1995),
pp. 279-354 [9412236], [doi] .
**Abstract:**

*We use the gauged linear sigma model introduced by Witten to calculate instanton expansions for correlation functions in topological sigma models with target space a toric variety V or a Calabi-Yau hypersurface M ⊂ V. In the linear model the instanton moduli spaces are relatively simple objects and the correlators are explicitly computable; moreover, the instantons can be summed, leading to explicit solutions for both kinds of models. In the case of smooth V, our results reproduce and clarify an algebraic solution of the V model due to Batyrev. In addition, we find an algebraic relation determining the solution for M in terms of that for V. Finally, we propose a modification of the linear model which computes instanton expansions about any limiting point in the moduli space. In the smooth case this leads to a (second) algebraic solution of the M model. We use this description to prove some conjectures about mirror symmetry, including the previously conjectured "monomial-divisor mirror map" of Aspinwall, Greene and Morrison. © 1995.*