upheld in collisions with black holes.

Since we have seen that the orbifold boundary condition itself is not sufficient to make negative tension compatible with black hole thermodynamics, it would be interesting to understand in more detail just what properties of these orientifolds enforce the second law. One suspects that one need only probe the details of the Atiyah-Hitchin manifold for the answers. A study of this form is currently in progress in collaboration with Simon Ross. We hope to report the results of this work soon.

[**Acknowledgments**]{}

In addition to the various acknowledgments in the original papers, I would like to thank Andrés Gomberoff, Simon Ross, and Mark Trodden for delightful collaborations on various parts of the work reported here. This work was supported in part by NSF grants PHY97-22362 and PHY00-98747 to Syracuse University, the Alfred P. Sloan foundation, and by funds from Syracuse University.

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