What is the work that the prize has been given for? Ashoke says, `The prize was given for my work on strong weak coupling duality symmetry, or in short, S-duality. While many symmetries are easy to
recognize, S-duality symmetry is hard to recognize since it relates a weakly coupled theory for which a lot is known, to a strongly coupled theory for which little is known. My work in the mid 90's involved devising specific strategy for detecting such symmetries, and I used it to find strong evidence for S-duality in a class of field theories and string theories. Later this strategy was used by others to discover many more such symmetries, and eventually led to the realization that the five different string theories known at that time are all related by such duality symmetries and hence actually describe different limits of the same underlying theory.'
Duality is well known in other contexts. In the context of the Ising model, a model of magnetic phenomena, the duality transformation is used to map phenomena at high temperatures to phenomena at low temperatures. The phenomena seen can be analysed by setting up perturbation expansions in terms of the temperature parameter, high temperature expansions at high temperatures, and low temperature expansions at low temperatures. Often the low temperature expansions are easy to analyse, and obey nice mathematical properties, whereas the high temperature once are not. Then duality can be used to map the insights obtained at low temperatures to understand the phenomena at high temperatures. In the case of gauge theories and string theories, the coupling, or the strength of interaction between particles plays the role of the temperature. Weakly coupled theories like electrodynamics, are well understood, strongly coupled ones like Quantum Chromodynamics are not. Here again, the duality transformation maps one extreme to another, and facilitates analysis. In the context of string theory, the generalization of the S-duality discovered by Ashoke, reduced the multiplicity of models studied via the insight, that they were different limits of the same theory.
We would like to finish with another quote from Ashoke. `In my opinion, a lot of Indian parents tend to dissuade their children from taking up physics, so for them an award like this might be an incentive, which is not necessarily a bad thing. However, if the youth were to start getting into physics only to have access to the prize money, then that would defeat the purpose.'
This blog post is by Neelima Gupte and Sumathi Rao.
(I would like to add a few personal lines. Ashoke is a close friend of Rahul as well as myself, and is of course, Sumathi's husband. This is a very proud day for all of us. -Neelima.)