A Note on Poly-Instanton Effects in Type IIB Orientifolds on Calabi-Yau   Threefolds
  The zero mode structure for the generation of poly-instanton corrections for Euclidian D3-branes wrapping complex surfaces in Type IIB orientifolds with O7- and O3-planes is analyzed. Working examples of such surfaces and explicit embeddings into compact Calabi-Yau threefolds are presented, with special emphasis on geometries capable of realizing the LARGE volume scenario. 
Ralph Blumenhagen, Xin Gao, Thorsten Rahn, Pramod Shukla
hep-th