Frederik Denef

Title: Wall crossing in orientifold compactifications

Abstract: Quantizing bound states of mutually nonlocal particles or  
black holes in four dimensions provides a simple physical derivation  
of various wall crossing formulae in N=2 theories. For model building  
applications, orientifolded versions of these theories are more  
relevant, however. This leads one to consider similar bound states in  
an orientifolded 4d spacetime, dubbed "orientiholes", giving rise to  
modified wall crossing formulae, as well as to tangible dual pictures  
of a number of subtle issues arising in the construction of D-brane  
vacua. Further applications are a new OSV-like formula and a new  
approach to vacuum statistics.