Cambridge Colloquium

The 1916 colloquium of the American Mathematical Society was held as part of the summer meeting that took place in Boston. Two sets of lectures were presented: Functionals and their Applications. There are selected topics, including ""Integral Equations"", by G. C. Evans, and ""Analysis Situs"", by Oswald Veblen. The lectures by Evans are devoted to functionals and their applications. By a functional the author means a function on an infinite-dimensional space, usually a space of functions, or of curves on the plane or in 3-space, etc. The first lecture deals with general considerations of functionals (continuity, derivatives, variational equations, etc.). The main topic of the second lecture is the study of complex-valued functionals, such as integrals of complex functions in several variables. The third lecture is devoted to the study of what is called implicit functional equations.This study requires, in particular, the development of the notion of a Frechet differential, which is also discussed in this lecture. The fourth lecture contains generalizations of the Bocher approach to the treatment of the Laplace equation, where a harmonic function is characterized as a function with no flux (Evans' terminology) through every circle on the plane. Finally, the fifth lecture gives an account of various generalizations of the theory of integral equations. Analysis situs is the name used by Poincare when he was creating, at the end of the 19th century, the area of mathematics known today as topology. Veblen's lectures, forming the second part of the book, contain what is probably the first text where Poincare's results and ideas were summarized, and an attempt to systematically present this difficult new area of mathematics was made.This is how S. Lefschetz had described, in his 1924 review of the book, the experience of ""a beginner attracted by the fascinating and difficult field of analysis situs"": ""Difficult reasonings beset him at every step, an unfriendly notation did not help matters, to all of which must be added, most baffling of all, the breakdown of geometric intuition precisely when most needed. No royal road can be created through this dense forest, but a good and thoroughgoing treatment of fundamentals, notation, terminology, may smooth the path somewhat. And this and much more we find supplied by Veblen's Lectures."" Of the two streams of topology existing at that time, point set topology and combinatorial topology, it is the latter to which Veblen's book is almost totally devoted.The first four chapters present, in detail, the notion and properties (introduced by Poincare) of the incidence matrix of a cell decomposition of a manifold. The main goal of the author is to show how to reproduce main topological invariants of a manifold and their relations in terms of the incidence matrix. The (last) fifth chapter contains what Lefschetz called 'an excellent summary of several important questions: homotopy and isotopy, theory of the indicatrix, a fairly ample treatment of the group of a manifold, finally a bird's eye view of what is known and not known (mostly the latter) on three dimensional manifolds'.