Potential theory grew out of mathematical physics, in particular out of the theory of gravitation and the theory of electrostatics. Mathematical physicists such as Poisson and Green introduced some of the central ideas of the subject. A mathematician with a general knowledge of analysis may find it useful to begin his study of classical potential theory by looking at its physical origins. Sections 2, 5 and 6 of these Notes give in part heuristic arguments based on physical considerations. These heuristic arguments suggest mathematical theorems and provide the mathematician with the problem of finding the proper hypotheses and mathematical proofs. These Notes are based on a one-semester course given by the author at Brown University in 1971. On the part of the reader, they assume a knowledge of Real Function Theory to the extent of a first year graduate course. In addition some elementary facts regarding harmonic functions are aS$umed as known. For convenience we have listed these facts in the Appendix. Some notation is also explained there. Essentially all the proofs we give in the Notes are for Euclidean 3-space R3 and Newtonian potentials ~.

During the last thirty years potential theory has undergone a rapid development, much of which can still only be found in the original papers. This book deals with one part of this development, and has two aims. The first is to give a comprehensive account of the close connection between analytic and probabilistic potential theory with the notion of a balayage space appearing as a natural link. The second aim is to demonstrate the fundamental importance of this concept by using it to give a straight presentation of balayage theory which in turn is then applied to the Dirichlet problem. We have considered it to be beyond the scope of this book to treat further topics such as duality, ideal boundary and integral representation, energy and Dirichlet forms. The subject matter of this book originates in the relation between classical potential theory and the theory of Brownian motion. Both theories are linked with the Laplace operator. However, the deep connection between these two theories was first revealed in the papers of S. KAKUTANI [1], [2], [3], M. KAC [1] and J. L. DO DB [2] during the period 1944-54: This can be expressed by the·fact that the harmonic measures which occur in the solution of the Dirichlet problem are hitting distri butions for Brownian motion or, equivalently, that the positive hyperharmonic func tions for the Laplace equation are the excessive functions of the Brownian semi group.

Annotation This volume consists of papers presented to the Second International Conference on the Theory of Groups held in Canberra in August 1973 together with areport by the chairman of the Organizing Committee and a collection of problems. The manuscripts were typed by Mrs Geary, the bulk of the bibliographie work was done by Mrs Pinkerton, and a number of colleagues helped with proof-reading; Professor Neumann, Drs Cossey, Kovacs, MeDougall, Praeger, Pride, Rangaswamy and Stewart. I here reeord my thanks to all these people for their lightening of the editorial burden. M.F. Newrnan CONTENTS 1 Introduction . . 8 yan, Periodic groups of odd exponent Reinhold Baer, Einbettungseigenschaften von Normalteilern: der Schluss vom 13 Endlichen aufs Unendliche D.W. Barnes, Characterisation of the groups with the Gaschutz cohomology property 63 Gi Ibert Baumslag, Finitely presented metabe1ian groups 65 Gi Ibert Baumslag, Some problems on one-relator groups 75 A.J. Ba, J. Kautsky and J.W. Wamsley, Computation in nilpotent groups (application) 82 Wi I I iam W. Boone, Between logic and group theory 90 Richard Brauer, On the structure of blocks of characters of finite groups 103 A.M. Brunner, Transitivity-systems of certain one-relator groups 131 Egg8r M. Bryant, Characteristic subgroups of free groups 141 y, Metabe1ian varieties of groups 150 R.A. Bryce and John Cossey, Subdirect product c10sed Fitting c1asses 158 R.G."

This is the proceedings volume of two mathematical meetings on Potential Theory organized in Bucharest, Romania, in September 2002 and September 2003. It includes six survey articles and seven selected research papers, covering the main topics of the conferences: geometric aspects in potential theory, Dirichlet structures, stochastic analysis, potential theory, and Markov processes.

Proceedings