This volume contains original research articles by many of the world's leading researchers in algebraic and Lie groups. Its inclination is algebraic and geometric, although analytical aspects are included. The central theme reflects the interests of R. W. Richardson, viz. connections between representation theory and the structure and geometry of algebraic groups. Particular topics addressed include Kazhdan-Lusztig theory, quantum groups, spherical varieties, symmetric varieties, cohomology of varieties, purity, Schubert geometry, invariant theory and symmetry breaking. The theory of canonical bases and their geometric context is a theme of several of the contributions as is the orbit theory of algebraic group actions on affine varieties. All workers on algebraic and Lie groups will find that this book contains a wealth of interesting material.