Grafting Boardman's Cherry Trees to Quantum Field Theory

Abstract

Michael Boardman has been a major contributor to the theory of infinite loop spaces and higher homotopy algebra. Indeed Boardman was the first to refer to `homotopy everything'. One particular contribution which has had major progeny is his use of `geometric' trees, combinatorial tress with lengths attached to edges. Here is a modified version of the talk given to honor Mike on the occassion of his 60th birthday. It is an idiosyncratic survey of parts of homotopy algebra from Poincaré to the present day, with emphasis on Boardman's original ideas, starting with his cubical subdivision of the associahedra through recent applications in mathematical physics via compactifications of moduli spaces.