This is a collection of contributed papers by former collaborators and colleagues of Claudio Bunster (formerly Teitelboim). The topics include General Relativity, Quantum Gravity, String Theory; from historical reviews to current research; from mathematical structures underlying the fundamental interactions, to cosmological scenarios describing the universe at its birth. Each contribution covers a topic in a self-contained manner, including all the references and illustrations to make it easy to read separately. The volume covers a number of important topics in theoretical physics of the last 30 years. Many of the seeds of string theory like supergravity, the AdS/CFT correspondence, p-form fields, electric-magnetic dualities, were discovered first in the context of gravitation by Bunster and his collaborators. This volume is rooted in this tradition and makes it an interesting source for theoretical physicists engaged in current research.

Putting the quantum into magnetism might, at first sight, seem like stating the obvious; the exchange interactions leading to collective magnetic behavior are, after all, a pure quantum effect. Yet, for many phenomena in magnetism this underlying quantum nature may be safely ignored at least on the qualitative level. The investigation of magnetic systems where quantum effects play a dominant role and have to be accounted for in detail has, over the last decades, evolved to be a field of very active research. On the experimental side, major boosts have come from the discovery of high-temperature superconductivity in the mid-eighties and the increasing ability of solid state chemists to fashion magnetic systems of restricted dimensionality. While hightemperature superconductivity has raised the question of the link between the mechanism of superconductivity in the cuprates and spin fluctuations and magnetic order in one- and two-dimensional spin-1/2 antiferromagnets, the new magnetic materials have exhibited a wealth of new quantum phenomena of interest in their own. In one-dimensional systems, the universal paradigm of Luttinger liquid behavior has come to the center of interest; in all restricted geometries, the interplay of low dimension, competing interactions and strong quantum fluctuations generates, beyond the usual long range ordered states, a wealth of new states of condensed matter, such as valence bond solids, magnetic plateaux, spin liquid states or spin-Peierls states, to name but a few.

Just how smart can computers get? Science journalist Julian Brown takes a hard look at the spooky world of quantum computation in Minds, Machines, and the Multiverse--and his report is optimistic. Based in large part on the groundbreaking work of David Deutsch, the book mostly sidesteps the shouting matches of the AI debate and instead explores the history of computation and quantum theory before turning to the exciting advances likely to come out of their merger. While some readers might cringe at the blithe dismissal of classical computing as a relic, Brown shows us why quantum computing is faster and more powerful, and is a good candidate for replacing its predecessor.

The author doesn't pull any mathematical punches, but injects enough humor and personalization into his writing to keep the book from crumbling to dust. Indeed, portraits of such luminaries as Deutsch and Feynman are more engaging than those found in some biographies and are enlightening on their own. But the real power and charm of Brown's prose lie in its straightforward explanation of the arcane details of the multiple-worlds theory, "qubits," and quantum logic in language any informed reader can understand. There are more questions than answers in Minds, Machines, and the Multiverse, but the questions are profoundly satisfying all by themselves. --Rob Lightner