The study of group actions is more than a hundred years old but remains
to this day a vibrant and widely studied topic in a variety of
mathematic fields. A central development in the last fifty years is the
phenomenon of rigidity, whereby one can classify actions of certain
groups, such as lattices in semi-simple Lie groups. This provides a way
to classify all possible symmetries of important spaces and all spaces
admitting given symmetries. Paradigmatic results can be found in the
seminal work of George Mostow, Gergory Margulis, and Robert J. Zimmer,
among others.
The papers in Geometry, Rigidity, and Group Actions explore the role
of group actions and rigidity in several areas of mathematics, including
ergodic theory, dynamics, geometry, topology, and the algebraic
properties of representation varieties. In some cases, the dynamics of
the possible group actions are the principal focus of inquiry. In other
cases, the dynamics of group actions are a tool for proving theorems
about algebra, geometry, or topology. This volume contains surveys of
some of the main directions in the field, as well as research articles
on topics of current interest.