Ashoke Sen: The Indian Physicist Wins 2026 Oskar Klein Medal for pioneering work on String Theory and Black Holes

Ashoke Sen, a theoretical physicist from India has been awarded the prestigious 2026 Oskar Klein Medal making him the first Indian physicist to win. He has been recognised for his pioneering work in the field of string theory such as S-duality, black holes and entropy and string field theory.

On the 22nd of October Ashoke Sen delivered the 2026 Oskar Klein Memorial lecture on ‘Gravity from Strings and Strings from Gravity’ at AlbaNova Centre at Stockholm University, Sweden. The news was announced by the International Centre for Theoretical Sciences (ICTS) as Sen is an ICTS-Infosys Madhava Chair Professor.

The Oskar Klein Medal was established in 1988 and is awarded annually by Stockholm University and the Nobel Committee for Physics at the Royal Swedish Academy of Sciences. It has been named after Oskar Klein, a Swedish theoretical physicist. Some previous winners of this award include Stephen Hawking, Peter Higgs, Steven Weinberg and Hans Bethe.

This latest award recognises Sen’s decades of achievements in theoretical physics and his work has enabled scientists to investigate connections between gravity, quantum mechanics and the fundamental nature of the universe.

Who is Ashoke Sen?

Sen was born on the 15th July 1956 in Kolkata. Sen is a renowned theoretical physicist from India.

He attended Shailendra Sircar Vidyalaya in Kolkata. He then went onto study physics at Presidency College. Afterwards Sen completed postgraduate studies at the Indian Institute of Technology (IIT) Kanpur and completed his doctorate in the USA.

Sen’s work focuses on complex mathematical problems.

He has looked at connecting seemingly unrelated theories and understanding properties of particular black holes in using quantum physics.

Sen left school with a Bachelor of Science in physics from Presidency College, Kolkata in 1975. Sen then completed his Master of Science in physics from IIT Kanpur in 1978.

He moved to the USA to complete his doctorate. He completed his PhD in physics from the State University of New York at Stony Brook in 1982.

After completing his doctorate Sen completed his postdoctorate at two top research institutes in the USA. Sen worked at Fermi National Accelerator Laboratory (Fermilab) from 1982 to 1985. Sen then worked at Stanford Linear Accelerator Centre (SLAC) from 1985 to 1988.

In 1988 Sen returned to India to work at the Tata Institute of Fundamental Research (TIFR) in Mumbai. In 1995 Sen moved to work at the Harish-Chandra Research Institute in Allahabad (Prayagraj). He has continued his research in theoretical physics.

Sen currently works at the International Centre for Theoretical Sciences, part of the Tata Institute of Fundamental Research (TIFR), in Bengaluru as an ICTS-Infosys Madhava Chair Professor.

Sen’s career has taken him across the globe.

What is String Theory?

It is helpful to know what string theory is to understand Sen’s achievements.

There are many ways to describe our universe in modern physics. General theory of relativity (developed by Albert Einstein) explains gravity and space-time. Quantum mechanics explains how matter and energy behave at a small scale.

However, it can be difficult to connect gravity with quantum mechanics.

String theory is one way of doing this. It suggests that the smallest components in nature may not be point-like particles but instead tiny one-dimensional strings. These would create different particles depending on how they vibrate.

This theory has provided researchers with useful mathematical tools to investigate gravity and quantum mechanics however it has not been experimentally proven to fully explain our universe.

Sen has contributed to the development and investigation of key mathematical relationships.

One of Sen’s major contributions was his work in S-duality. This describes connections between certain theories when interactions are either strong or weak.

This is important because calculations can become very complex when interactions are strong. If there is another theory which describes these weak interactions they can be used to help investigate parts of the original theory.

Sen’s work helped to discover key connections between different string theories. Sen and other physicists’ research helped further the knowledge that five seemingly separate superstring theories could actually be connected as different limits of a more fundamental theory.

This helped form the second superstring revolution in the 1990s and influenced future research.

This contributed to Sen winning the Breakthrough Prize in Fundamental Physics in 2012.

Black holes

Sen has contributed significantly to theoretical physics in the area of black holes.

Black holes are regions in space-time where the gravity is so strong nothing can escape the event horizon not even light.

Black hole entropy has been investigated by physicists for many years. Black hole entropy relates to how many microstates are compatible with the macroscopic properties of a black hole.

Sen developed the entropy function formalism to investigate the entropy of particular extremal black holes. His work helped connect calculating black hole entropy with counting microstates in string theory.

This can be simplistically described as investigating how certain black holes can be understood using their quantum states.

Whilst not all mysteries surrounding black holes have been solved Sen’s work has provided important tools for understanding the connections between gravity, quantum mechanics and the microstates of matter.

His work in string field theory and investigating unstable states in string theory have influenced modern theoretical physics.

Achievements

Sen has won many prestigious awards.

ICTP Prize (1989)

Shanti Swarup Bhatnagar Prize in Physical Sciences (1994)

Fellow of the Royal Society (1998)

Padma Shri (2001)

Infosys Prize in Mathematical Sciences (2009)

Breakthrough Prize in Fundamental Physics (2012)

Padma Bhushan (2013)

Dirac Medal (2014)

International Honorary Member of the American Academy of Arts and Sciences (2026)

In 2013 Sen was awarded honorary degrees. He received a Doctor of Science degree from IIT Bombay and a Doctor of Literature degree from Jadavpur University.

This latest award is another prestigious award Sen has won. It recognises his work in helping progress some of the most mathematically challenging areas in theoretical physics.

Why is this important?

Sen’s career demonstrates the less obvious side of science. His work can take a long time to develop and can take years if not decades to influence a wider field.

Theoretical physics does not always have immediate applications but much of the progress comes from discovering mathematical connections and ensuring concepts are consistent. New ways of thinking about problems are also developed.

String theory is still an active area of research and has not been experimentally proven to fully describe nature. Sen’s achievements should be seen as his personal contributions to theoretical physics.

Sen’s journey from Kolkata to international recognition demonstrates the role India has had in fundamental research. Sen attended institutions in India and a large part of his career has been spent progressing research in India.

The Oskar Klein Medal will draw attention to a scientist who has helped physicists investigate connections between theories explaining our universe.

Overall, this demonstrates how decades of research into gravity, black holes and string theory continue to influence how scientists investigate the fundamental laws of nature.