Few people studying Gauge Field Theory need to be convinced of the importance of the work of 't Hooft. This volume contains a selection of articles and review topics covering his well-known studies on the renormalization of non-Abelian gauge theorems, topological phenomena in gauge field theory and thoughts on the role of black holes in quantum gravity.The chapters are tied together by thoughtful commentaries which provide a background and the illumination of hindsight — together they form a clear and coherent picture of the physical and theoretical importance of gauge theories and the gauge principle. This book is ideal for students and researchers.Gerard 't Hooft is Professor of Theoretical Physics at the University of Utrecht, The Netherlands. He has taught at Harvard, SLAC and Caltech prior to his present position. Other distinguished honors include being awarded the Dannie Heineman Prize, the Honorary Doctorate of Science from the University of Chicago, Wolf Prize of the State of Israel, Pius XI Medal (Vatican), and the Lorentz Medal (KNAW, Amsterdam).

This book presents an account of the exact solution of the Hubbard model in one dimension. The early chapters develop a self-contained introduction to Bethe's ansatz and its application to the one-dimensional Hubbard model. The later chapters address more advanced topics.

This book provides the first systematic discourse on a very peculiarapproach to the theory of strongly correlated systems. HubbardX-operators have been known for a long time but have not been widelyused because of their awkward algebra. The book shows that it ispossible to deal with X-operators even in the general multilevel localeigenstate system, and not just in the case of the nondegenerateHubbard model. X-operators provide the natural language for describingquasiparticles in the Hubbard subbands with unusual doping andtemperature-dependent band structures.