Obituary: Vanamamalai Seshadri (1928-2020)

Vanamamalai Seshadri

Vanamamalai Seshadri, Professor Emeritus of Statistics at McGill University, died peacefully at his daughter’s home on March 8, 2020, in Sunnyvale, California. He was 91 years old.

Sesh, as he was informally called, was born on April 25, 1928, in Kizhanatham, India. After studying mathematics at Loyola College in Madras (MA, 1950), he taught in Sri Lanka (1950-54) and Myanmar (1954-57) before moving to the United States to pursue doctoral studies in mathematical statistics at Oklahoma State University (PhD, 1961). His thesis, titled “Estimation in the Balanced Incomplete Block Design,” was written under the supervision of the eminent statistician Franklin Graybill. After graduation, Sesh taught at Southern Methodist University in Dallas, Texas, until 1962. He then moved his family to Montréal, where he began his career at McGill University. He was tenured in 1964 and became a Full Professor in 1970. He retired in 1997 and was made an Honorary Member of the Statistical Society of Canada in 2001.

Sesh’s research specialization was distribution theory. His name is permanently associated with the inverse Gaussian distribution, the long and fruitful study of which he began in 1981. His masterly exposition of the topic, titled “The Inverse Gaussian Distribution: A Case Study in Exponential Families,” was published in 1992 by Oxford University Press. He complemented it in 1999 with a second monograph titled “The Inverse Gaussian Distribution: Statistical Theory and Applications,” which appeared in the Springer Lecture Notes Series. Together, these two books are still the go-to references on the subject.

However, Sesh’s research contributions covered a much wider spectrum. In the early sixties, he started his research career by working on estimation problems. He proposed ways of combining independent estimators of a parameter that could be considered as cousins of Stein’s shrinkage estimator. He also wrote papers on topics in probability dealing, among others, with stable laws and tail probabilities. There is also a torrent of ideas and techniques in his work on multivariate analysis where he introduced a new method for constructing multivariate distributions on the unit simplex, and used continued fractions and random walks on certain semi-groups. Moreover, he used multivariate Laplace transforms to study the link between laws with quadratic variance functions and their conjugate counterparts. This latter work is in fact related to that which he did on natural exponential families of distributions, and the inverse Gaussian family.

While at McGill, Sesh authored over 50 research articles, many of which appeared in journals of the highest caliber such as The Annals of Statistics, the Journal of the American Statistical Association, and Biometrics. He was also a frequent contributor to The Canadian Journal of Statistics. In many of these papers, he was the sole author while in others he collaborated with world-class probabilists and statisticians such as Miklós Csörgö (Carleton), Michael Stephens (Simon Fraser), Gérard Letac (Toulouse), and Ole Barndorff-Nielsen (U. of Aarhus). He also supervised 9 MSc and 2 PhD students, several of whom proceeded to academic positions, including Morty Yalovsky and Christina Wolfson (McGill), Paul Cabilio (Acadia), Brenda MacGibbon (UQAM), Jonathan Shuster (U. of Florida), Sana El-Khoraibie (U. of Cairo), and Alain Vandal (U. of Auckland).

Within the Mathematics and Statistics Department at McGill, Sesh was known as an incurable traveler. His reputation and enthusiastic talks, delivered in English and French, earned him invitations from around the world and fed his wanderlust. In his retirement, he spent many years teaching at prestigious universities all over the world as Professor Emeritus, enjoying bridge games with his friends and spending time with his dear departed wife, Champa Seshadri.

Sesh is survived by his sister Leelavathi Seshadri, his children (Srinivasan Seshadri and Usha Seshadri), and various in-laws (Ikuko Fukuta Seshadri, Lakshmi Seshadri, Michael Kreaden, and Marie-Christine Guiot). He is mourned by his seven grandchildren: Olivia Seshadri, Annapurna Kreaden, Siddartha Kreaden, Masashi and Satoko Sato, and Masatoshi and Alex Sato. We are all the poorer for his departure but the discipline of statistics is richer for his exceptional research contributions.



by C. Genest and D.B. Wolfson, McGill University, Montréal

Wednesday, March 11, 2020

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