Removal of closed time-like curves by supertube domain walls

We discuss how closed time-like curves can be eliminated from certain supergravity backgrounds by inclusion of domain-walls made of supertubes. Special emphasis is given to the mechanism by which the supertubes spread into domain walls, which is similar to the enhanceon mechanism. Lecture notes from my talk at the RTN meeting in Kolymbari, Crete, September 2004.