The subject of this book is inverse theorems in additive number theory.
The major results are due to Vosper, Kneser, and Freiman. The goal of
the chapters in this preprint is to give a self-contained account of
Ruzsa's proof of Freiman's inverse theorem. The only prerequisite is
elementary number theory. I include proofs of such ``standard'' results
as Menger's theorem in graph theory and Minkowski's theorem on successive
minima in the geometry of numbers.
This is a preliminary version of the text. Some chapters are not yet written,
or are incomplete. Other chapters have not been checked, and contain
typographical and mathematical errors. I ask the reader to be patient with
the manuscript, and to send me comments and corrections, both substantive and
typographical, no matter how trivial. My e-mail address is:
nathansn@dimacs.rutgers.edu.
I wish to thank Imre Z. Ruzsa for providing me with preprints of his
papers on Freiman's theorem, Endre Szemer\'edi for describing to me his
joint result with Antal Balog, and Gregory Freiman for valuable discussions
about his work.