Award-winning theoretical physicist Ashoke Sen has focused on string theory

Dr. Ashoke Sen. File

Theoretical physicist Ashoke Sen has been awarded the 2026 Oskar Klein Medal, becoming the first Indian laureate to receive the honour, awarded by Stockholm University and the Nobel Committee for Physics of the Royal Swedish Academy of Sciences.

The Medal recognises significant contributions to theoretical physics. Dr. Sen is the ICTS-Infosys Madhava Chair Professor at the International Centre for Theoretical Sciences (ICTS), Bengaluru. He also delivered the memorial lecture accompanying the Medal in Stockholm on October 22, under the title ‘Gravity from Strings and Strings from Gravity’.

In his career, Dr. Sen has focused on string theory, which is the name of an attempt by physicists to describe matter and nature’s fundamental forces, including gravity, within a single framework called quantum gravity. Currently, they are split across two frameworks, quantum physics and relativity. String theory offers ways to reconcile them, but while it is mathematically a highly evolved theory, it has been unable to make predictions that can be confirmed with experiments using today’s technologies.

In the 1980s, Dr. Sen helped establish how the equations describing hypothetical strings moving through space could relate to the equations that describe the physical fields that surround it. In the 1990s, he helped show that two apparently different ways to describe physical forces were really equivalent, an idea called S-duality.

He also proposed three related ideas, together called the Sen conjectures, in 1999 that gave physicists new ways to understand the behaviour of the strings of string theory.

Dr. Sen graduated from Presidency College in Kolkata before going to IIT-Kanpur and thereon to earning his PhD from Stony Brook University, New York, in 1982. After working at institutions including the Tata Institute of Fundamental Research (TIFR) in Mumbai and the Harish-Chandra Research Institute (HRI) in Prayagraj, he moved to ICTS in 2021. For his work, he has won the S.S. Bhatnagar Prize (1994), the Infosys Prize (2009), the Breakthrough Prize in Fundamental Physics (2012), and the Dirac Medal (2014).

He also received the Padma Shri in 2001 and the Padma Bhushan in 2013.

The impact of Dr. Sen’s contributions has exceeded their own ambit. In one 2014 interview, U.S. theoretical physicist Edward Witten — widely considered to be the greatest living mathematical physicist — called one of Dr. Sen’s papers “short but brilliant” and that it “convinced me that the duality had to be right”. Dr. Witten also said Dr. Sen’s findings had inspired work that paved the way for more breakthroughs in understanding how subatomic particles interact with each other.

He has also done important work on black holes. Physicists had long known that these enigmatic cosmic beasts had entropy but could not explain its origins in their physical theories. Dr. Sen developed mathematical methods to make sense of a black hole’s microscopic states in a way that could account for its observable, macroscopic characteristics.

Together, many physicists agree, his contributions have considerably advanced the theories physicists use to understand quantum gravity.

The Oskar Klein Medal and the accompanying Memorial Lectures were launched in 1988 to honour the Swedish physicist Oskar Klein (1894-1977). In 1926, Klein, building on the work of German mathematician Theodor Kaluza, explored whether electromagnetism and gravity could be described in a common framework by introducing an extra dimension of space. The result, known as Kaluza-Klein theory, exerted a significant influence on later attempts by physicists — including string theory — to unify these forces.

India in particular has an influential community of string theorists, especially at TIFR Mumbai, ICTS Bengaluru, HRI Prayagraj, and the Indian Institute of Science Education Research in Pune. Aside from Dr. Sen, the community’s notable members include Nabamita Banerjee, Shiraz Minwalla, Sunil Mukhi, P. Ramadevi, and Spenta Wadia.

science (general) / physics / physics (education)