He developed a fundamental formalism called dynamical maps to study the theory of open quantum system. He, in collaboration with Baidyanath Misra, also proposed the quantum Zeno effect. Sudarshan and collaborators initiated the "Quantum theory of charged-particle beam optics", by working out the focusing action of a magnetic quadrupole using the Dirac equation. He taught at the Tata Institute of Fundamental Research (TIFR), University of Rochester, Syracuse University, and Harvard. From 1969 onwards, he was a professor of physics at the University of Texas at Austin and a senior professor at the Indian Institute of Science. He worked as the director of the Institute of Mathematical Sciences (IMSc), Chennai, India, for five years during the 1980s dividing his time between India and USA. During his tenure, he transformed it into a centre of excellence. He also met and held many discussions with philosopher J. Krishnamurti. He was felicitated on his 80th birthday, at IMSc Chennai on 16 September 2011. His areas of interest included elementary particle physics, quantum optics, quantum information, quantum field theory, gauge field theories, classical mechanics and foundations of physics. He was also deeply interested in Vedanta, on which he lectured frequently. Controversy regarding Nobel Prize Sudarshan began working on quantum optics at the University of Rochester in 1960. Two years later, Glauber criticized the use of classical electromagnetic theory in explaining optical fields, which surprised Sudarshan because he believed the theory provided accurate explanations. Sudarshan subsequently wrote a paper expressing his ideas and sent a preprint to Glauber. Glauber informed Sudarshan of similar results and asked to be acknowledged in the latter's paper, while criticizing Sudarshan in his own paper. "Glauber criticized Sudarshan’s representation, but his own was unable to generate any of the typical quantum optics phenomena, hence he introduces what he calls a P-representation, which was Sudarshan’s representation by another name", wrote a physicist. "This representation, which had at first been scorned by Glauber, later becomes known as the Glauber–Sudarshan representation." Sudarshan was passed over for the Physics Nobel Prize on more than one occasion, leading to controversy in 2005 when several physicists wrote to the Swedish Academy, protesting that Sudarshan should have been awarded a share of the Prize for the Sudarshan diagonal representation (also known as Glauber–Sudarshan representation) in quantum optics, for which Roy J. Glauber won his share of the prize. Sudarshan and other physicists sent a letter to the Nobel