Acknowledgements

This book benefited greatly from the generous help of many colleagues and friends. We are especially grateful to Lincoln Wolfenstein for his generous support and advice over the years, for countless conversations, for the critical reading of various parts of the draft, and for enlightening discussions during his visit to Lisbon. Special thanks also go to Boris Kayser for the many conversations that we had during his visit to Lisbon.

Our colleagues Evgeny Akhmedov, Augusto Barroso, Stefano Bertolini, Francisco Botella, Jean-Marc Gérard, Walter Grimus, Hans-Günther Moser, Mário Santos, and Helmut Vogel have read and criticized parts of the draft. We thank them for their many comments and suggestions. Needless to say, ours is the blame for any inadequacies that remain.

Gustavo Castelo Branco is thankful to Rabindra Mohapatra for having introduced him to the subject of this book, two decades ago. We are also grateful to António Amorim, Andrea Brignole, John Donoghue, Ricardo González Felipe, Paulo Parada, Margarida Nesbitt Rebelo, Jorge Romão, Luca Silvestrini, João Soares, and Alfred Stadler for discussions.

We are indebted to Marc Baillargeon and Paulo Nogueira for allowing us to use, before public release, their excellent software ‘Scribble’, with which most Feynman graphs have been drawn.

João Paulo Silva thanks the Instituto Superior de Engenharia de Lisboa for relieving him from his teaching duties during the Fall semester of 1997. We also want to thank many of our colleagues and the staff at the Centro de Física das Interaçõdes Fundamentais and at the Centro de Física Nuclear da Universidade de Lisboa, in particular Ana Eiró, who helped us on various occasions. Ricardo González Felipe, Paulo Nogueira, Pedro Sacramento, and Vítor Rocha Vieira have helped solving various computer problems. Eduardo Lopes rescued portions of the book from a crashed computer hard disk.

Our editor, Soenke Adlung, has provided us with friendly and valuable advice along the way. We are also indebted to the staff of Oxford University Press, especially to Kim Roberts and to Julia Tompson, for their help in the preparation of the manuscript.

Finally, we wish to thank our families for their forbearance and relentless support. To some extent, this book is as much theirs as it is ours. Luís Lavoura wants to dedicate this book to the memory of his mother, who died shortly before completion of the manuscript.