**
Albrecht Klemm
**

**Omega backgrounds and generalized
holomorphic anomaly equation
**

**Abstract
**

We derive an anomaly equation which incorporates the general Omega background in the B-model. We discuss applications to topological string theory on Calabi-Yau backgrounds and N = 2 gauge theory with massive flavors. Using geometric engineering on the Enriques Calabi-Yau we derive Seiberg-Witten curves for the conformal cases, which are compatible with Nekrasovs partition function.