Amal Kumar Raychaudhuri

Amal Kumar Raychaudhuri, also known as AKR, was an Indian physicist who made significant contributions to the fields of general relativity and cosmology. He is best known for deriving the Raychaudhuri equation, which describes the evolution of a congruence of timelike or null geodesics in a curved spacetime. The equation shows that under certain conditions, the geodesics will converge to a singularity, implying that the spacetime is incomplete. This result was a key ingredient in the proofs of the Penrose–Hawking singularity theorems, which established that singularities are inevitable in general relativity. Raychaudhuri was born in a Baidya family in Barisal, East Bengal, British India (now Bangladesh) on 14 September 1923. He moved to Kolkata with his family when he was a child. He had a passion for mathematics since his schooldays and was praised by his teachers for his original solutions. He graduated from Presidency College in 1942 and obtained his M.Sc. degree from Science College campus of Calcutta University in 1944. He joined the Indian Association for the Cultivation of Science (IACS) in 1945 as a research scholar, but was not satisfied with working on experimental physics. He developed an interest in general relativity and studied it on his own from books and papers. In 1952, he returned to IACS as a research officer, but was still required to work on the properties of metals rather than general relativity. Despite these difficulties, he managed to derive and publish the equation that bears his name in 1955. The paper was well received by notable physicists such as Pascual Jordan and John Archibald Wheeler. In 1959, he submitted his doctoral dissertation based on his paper and received his D.Sc. degree from the University of Calcutta. In 1961, he joined the faculty of his alma mater, Presidency College, where he taught physics until his retirement in 1986. He was revered as a teacher by his students and colleagues. He also continued his research on general relativity and cosmology, exploring topics such as gravitational collapse, cosmic censorship, quantum cosmology, inflationary models, and dark energy. He supervised several doctoral students, including Ashoke Sen, who became a renowned string theorist. Raychaudhuri was elected as a member of the International Committee on General Relativity and Gravitation for the period 1974–83. He was also the president of the Indian Association of General Relativity and Gravitation during 1980–82. He was elected as a fellow of the Indian Academy of Sciences in 1982 and the Indian National Science Academy in 1987. He received several awards and honors for his work, such as the Meghnad Saha Medal (1986), the S.N. Bose Medal (1998), and the Padma Shri (2001). Raychaudhuri married Nomita Sen in 1958 and had four children. He led a simple and stress-free life. He was interested in politics and social issues and wrote several essays on them. He also enjoyed music, literature, and chess. He died of a heart attack on 18 June 2005 in Kolkata.