Random walks, Markov chains and electrical networks serve as an
introduction to the study of real-valued functions on finite or infinite
graphs, with appropriate interpretations using probability theory and
current-voltage laws. The relation between this type of function theory
and the (Newton) potential theory on the Euclidean spaces is
well-established. The latter theory has been variously generalized, one
example being the axiomatic potential theory on locally compact spaces
developed by Brelot, with later ramifications from Bauer, Constantinescu
and Cornea. A network is a graph with edge-weights that need not be
symmetric. This book presents an autonomous theory of harmonic functions
and potentials defined on a finite or infinite network, on the lines of
axiomatic potential theory. Random walks and electrical networks are
important sources for the advancement of the theory.