Kalyanapuram Rangachari Parthasarathy

Kalyanapuram Rangachari Parthasarathy (25 June 1936 – 14 June 2023) was an Indian statistician who was professor emeritus at the Indian Statistical Institute and a pioneer of quantum stochastic calculus. Parthasarathy was the recipient of the Shanti Swarup Bhatnagar Prize for Science and Technology in Mathematical Science in 1977 and the TWAS Prize in 1996.

Biography Parthasarathy was born on 25 June 1936 in Madras, into a modest but deeply religious Hindu Brahmin family. He completed his early years of schooling in Thanjavur, before moving back to Madras to complete his schooling from P. S. School in the Mylapore neighbourhood of the city. He went on to study at the Ramakrishna Mission Vivekananda College, where he completed the B.A. (Honours) course in Mathematics.

Parthasarathy then moved to Kolkata to attend the Research and Training school at the Indian Statistical Institute, where he completed his PhD, under the supervision of C. R. Rao in 1962. He was one of the "famous four" at ISI from 1956 to 1963, alongside Ramaswamy Ranga Rao, Veeravalli S. Varadarajan, and S. R. Srinivasa Varadhan. He was awarded the first Ph.D. degree of ISI.

Parthasarathy was married to Shyama Parthasarathy. The couple had two sons.

Research Parthasarathy started his work on theoretical probability during his time at the Indian Statistical Institute. During this time, he continued to focus on the foundations of probability theory.

After returning to India, he spent a few years at Bombay University and the Indian Institute of Technology, Delhi, before returning to the new Indian Statistical Institute, Delhi Centre in 1976, where he spent the next 20 years before retiring in 1996. along with S.R.S. Varadhan, R. Ranga Rao and Veeravalli S. Varadarajan, which they introduced in 1967. The PRV paper arose out of the grand program of Harish-Chandra on the representation theory of real connected semisimple Lie groups.

Parthasarathy, K. R., Ranga Rao, R., & Varadhan, S. R. S. (1962). On the category of indecomposable distributions on topological groups. Transactions of the American Mathematical Society, 102(2), 200-217.