A Twinkle in the Eyes

Abstract

My memory is becoming increasingly porous, but I believe I first met Walter in February of 1965, in San Diego, during a short reprieve from the winter besetting the University of Chicago (and I deduce from this that Walter must have been on the right side of 40 then). At Cambridge, where I had studied for my Ph.D., I had made very close acquaintance with the metallic state of matter. But the insulating state, in a fully many-body context, was a puzzle to me then. Walter had written some beautiful papers on this topic, and in early 1965 began to set me on the right path. I thought then (and do so now) that he was one of the most congenial of men, and that he was endowed, as we all know, with the most extraordinary physical insight and perspicacity. The nearly four decades that have since passed have only served to solidify my view; in fact during this period I simply cannot count the number of times that, tracking back through the literature on a particular research topic in condensed matter theory, I have ended up at a seminal paper of Walter’s. It is abundantly clear that he has had a profound impact not only on our chosen field, but on allied fields as well. His remarkable creation of the density functional approach to correlated quantum systems has actually far transcended theoretical condensed matter physics per se.