Alladi Ramakrishnan (1923–2008) was an eminent scientist who had a wide range of research interests in theoretical and mathematical physics. Professor Ramakrishnan made significant contributions to probability and statistics, elem- tary particle physics, cosmic rays and astrophysics, matrix theory, and the special theory of relativity. Ramakrishnan believedstrongly that in addition to doing fun- mental research, one must contribute to the advancementof the profession. Inspired by his visit to the Institute for Advanced Study in Princeton in 1957–1958, he returned to Madras and began the Theoretical Physics Seminar at his family home Ekamra Nivas. These seminars were ultimately responsible for the creation of MATSCIENCE, The Institute of Mathematical Sciences in 1962. This institute, of which he was the Director for its first 21years, has grown steadily in size and stature, and is his monumental contribution to the profession. In a distinguished scientific life that has spanned more than five decades, Professor Ramakrishnan has come into close contact with, and was influenced by, several eminent mathema- cians and physicists, and has moulded the careers of his several students and young researchers. This volume, which is a tribute to his great legacy, not only deals with his significant contributions to research and the profession, but also contains a—ne collection of research and survey papers by leading physicists and mathematicians that cover a broad range of areas in the mathematical sciences.