Quantum Gravity

viiiPrefaceIt is clear that my book could not have been written in this form withoutthe influence of many people over the past 20 years. I am in particular indebtedto H.-Dieter Zeh for encouraging me to enter this field of research and for manystimulating and inspiring interactions. I also thank Norbert Straumann in Zürichand Hartmann Römer in Freiburg for providing me with the excellent workingconditions that gave me the freedom to follow the research I wanted to do.Many people have read through drafts of this book, and their critical commentshave helped me to improve various parts. I owe thanks to Julian Barbour, AndreiBarvinsky, Domenico Giulini, Alexander Kamenshchik, Thomas Mohaupt,Paulo Moniz, Andreas Rathke, Thomas Thiemann, and H.-Dieter Zeh. I am alsodeeply indebted to them and also, for discussions over many years, to MariuszD¸abrowski, Lajos Diósi, Petr Hájíček, Erich Joos, Jorma Louko, David Polarski,T. P. Singh, Alexei Starobinsky, and Andreas Wipf. I have actively collaboratedwith most of the aforementioned theoreticians and I want to take thisopportunity to thank them for the pleasure that I could experience during thesecollaborations.CologneJanuary 2004Claus Kiefer