This book is aimed at readers with a strong background in linear algebra and advanced calculus. Early chapters develop representation theory of compact Lie groups with applications to topology, geometry, and analysis. Later chapters study the structure of representation theory and analysis of non-compact semi-simple Lie groups. Helpful Appendixes develop aspects of differential geometry, Lie theory, and functional analysis used in the main text. AUTHOR: Nolan R. Wallach is Professor of Mathematics at the University of California, San Diego. In early 2018, Dover will also publish the second edition of his Symplectic Geometry and Fourier Analysis.