Synopsis This book is a collection of expository articles by well-known mathematicians. Some of them introduce the reader to a major topic while others provide a glimpse into an active field of research. All articles are accessible to graduate students. The articles were invited in honour of K.R. Parthasarathy, a mathematician, teacher and expositor of renown. Some of the articles, by his coworkers, are related to his work on probability, quantum probability and group representations. Others are on diverse topics in analysis geometry and number theory.Texts and Readings in Mathematics-10