## Abstract

Our goal in this paper is to discuss a conjectural correspondence between the enumerative geometry of curves in Calabi-Yau 5-folds Z and 1-dimensional sheaves on 3-folds X that are embedded in Z as fixed points of certain C^{×}-actions. In both cases, the enumerative information is taken in equivariant K-theory, where the equivariance is with respect to all automorphisms of the problem. In Donaldson-Thomas theory, one sums over all Euler characteristics with a weight (-q)^{x}, where q is a parameter, informally referred to as the boxcounting parameter. The main feature of the correspondence is that the 3-dimensional boxcounting parameter q becomes in dimension 5 the equivariant parameter for the C^{×}-action that defines X inside Z. The 5-dimensional theory effectively sums up the q-expansion in the Donaldson-Thomas theory. In particular, it gives a natural explanation of the rationality (in q) of the DT partition functions. Other expected as well as unexpected symmetries of the DT counts follow naturally from the 5-dimensional perspective. These involve choosing different C^{×}-actions on the same Z, and thus relating the same 5-dimensional theory to different DT problems. The important special case Z = X×C^{2} is considered in detail in Sections 7 and 8. If X is a toric Calabi-Yau 3-fold, we compute the theory in terms of a certain index vertex. We show that the refined vertex found combinatorially by Iqbal, Kozcaz, and Vafa is a special case of the index vertex.

Original language | English |
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Pages (from-to) | 320-369 |

Number of pages | 50 |

Journal | Algebraic Geometry |

Volume | 3 |

Issue number | 3 |

DOIs | |

Publication status | Published - 1 May 2016 |

Externally published | Yes |

## Keywords

- Donaldson-Thomas theory
- M-theory