By P Chandra, P Coleman, G Kotliar, P Ong, D L Stein and C Yu (eds)
World Scientific
In December 2013, a community of physicists gathered in Princeton on the occasion of Philip Warren Anderson’s 90th birthday to celebrate the achievements of his remarkable career. This book is the result of the event, and collects a number of intriguing and lively contributions from Anderson’s students, collaborators and distinguished colleagues, which will appeal to both high-energy and condensed-matter physicists.
The description of a single helium atom is familiar to any undergraduate student, but a collection of many helium atoms produces unexpected phenomena ranging from superfluidity to magnetic phases. This occurrence could be concisely summarised by saying that “more is different”, as Anderson (who shared the 1977 Nobel Prize in Physics with N Mott and J Van Vleck for their fundamental theoretical investigations of the electronic structure of magnetic and disordered systems) wrote in the title of a pedagogical article published in 1972. As Anderson would put it, “the ability to reduce everything to simple fundamental laws does not imply the ability to start from these laws and reconstruct the whole universe.” The so-called “emergentism” appears then as a possible synthesis between the thesis of the reductionism (often attributed to particle physics) and the antithesis of pure constructivism. This third perspective can be appreciated in this book.
Relatively short, it contains accurate and stimulating accounts of various hot topics that are popular in condensed-matter theory, starting from the ubiquitous mechanism of the localisation of waves in random media (often referred to as “Anderson localisation”). The connections between superfluidity, superconductivity and the way that massless gauge bosons acquire a mass are explored in the contribution of Frank Wilczek (who shared the 2004 Nobel Prize in Physics with David Gross and David Politzer, for the discovery of asymptotic freedom).
The historical origins of Anderson’s paper describing the relation between plasmons, gauge invariance and mass are masterly reviewed by Ed Witten (professor of mathematical physics at the Institute for Advanced Study in Princeton, US).
In a nutshell, Anderson’s idea was that the scalar zero-mass excitations of a superconducting neutral Fermi gas become longitudinal plasmon modes of finite mass when the gas is charged. Higgs described his mechanism as the relativistic analogue of Anderson’s idea, whose origin is instead conceptually motivated by a series of contributions by J Schwinger, speculating that gauge fields can become massive thanks to strong coupling effects in two space–time dimensions. This field theory in two dimensions is often used to introduce the concept of “bosonisation”.
The contributions contained in PWA90 can be considered as an extended introduction to a more technical treatise (very popular among practitioners in the late 1980s and early 1990s) entitled Basic Notions of Condensed Matter Physics (Benjamin-Cummings 1984) and edited by P W Anderson together with C C Yu. In that book, Anderson managed to stress the connection between symmetry breaking, emergent phenomena and condensed-matter theory. While more than 30 years separate the two books, their common goals and inspirations remain intact: different areas of physics can and must be cross-fertilised because, ultimately, physics is one.
