BY HARRY KESTEN
FRANK SPITZER WAS A highly original probabilist and a humorous, charismatic person, who had warm relations with students and colleagues. Much of his earlier work dealt with the topics of random walk and Brownian motion, which are quite familiar to probabilists. Spitzer invented or developed quite new aspects of these, such as fluctuation theory and potential theory of random walk (more about these later); however, his most influential work is undoubtedly the creation of a good part of the theory of interacting particle systems. Through the many elegant models that Frank constructed and intriguing phenomena he demonstrated, a whole new set of questions was raised. These have attracted and stimulated a large number of young probabilists and have made interacting particle systems one of the most exciting and active subfields of probability today.
Frank Spitzer was born in Vienna, Austria, on July 24, 1926, into a Jewish family. His father was a lawyer. When Frank was about twelve years old his parents sent him to a summer camp for Jewish children in Sweden. Quite possibly the intention of this camp was to bring out Jewish children from Nazi-held or Nazi-threatened territory. Be that as it may, Frank's parents soon informed him that the situa-