| Enumerative questions have a very long history in Mathematics and have been subject to a significant revival in the nineties with the construction of the moduli space of stable maps and the machinery which allows us to integrate on these very singular spaces. However, moduli spaces of stable maps have many "unwanted" components which are reflected in the intersection numbers. In this talk I will discuss the meaning of genus one Gromov-Witten invariants of three folds. |