
10 Acknowledgements
The materials presented here originated from research work of BLH
with Antonio Campos, Nicholas Phillips, Alpan Raval, and Sukanya
Sinha, and of EV with Rosario Martin and Albert Roura. We thank
them as well as Daniel Arteaga, Andrew Matacz, Tom Shiokawa, and
Yuhong Zhang for fruitful collaboration and their cordial
friendship since their Ph.D. days. We enjoy lively discussions
with our friends and colleagues Esteban Calzetta, Diego Mazzitelli,
and Juan Pablo Paz whose work in the early years contributed toward
the establishment of this field. We acknowledge useful discussions
with Paul Anderson, Larry Ford, Ted Jacobson, Renaud Parentani, and
Raphael Sorkin. This work is supported in part by NSF grant
PHY98-00967, the MICYT Research Project No. FPA-2001-3598, and
the European project HPRN-CT-2000-00131.
