Non-perturbative corrections in IIB orientifolds

The schedule for this Journal Club on String Theory will be as follows: 

1)  The latest news in the world of strings 

Please bring papers that caught your recent attention and briefly summarize motivations, methods and results. 

2) Non-perturbative corrections in IIB orientifolds 

Gabriele Honecker will lead a discussion on:  

"Non-perturbative corrections in IIB orientifolds" 

Abstract:
Non-perturbative corrections to the Kaehler potential in N=1 IIB orientifold compactifications arise from 
both b-field moduli and D-instantons. Following 0705.2353 I am discussing these effects and how they 
constrain the non-perturbative superpotential. 
Compactification on the Enriques Calabi-Yau serves as a simple example.

References:  
e-Print Archive:  arXiv:0705.3253v2 [hep-th]