Shamik Banerjee, a theoretical physicist working in the Institute of Physics (IOP), Bhubaneswar, and a SwarnaJayanti fellowship awardee of 2020-21, seeks to understand the origin of the universe and probe into what happens at the centre of a Black Hole by unraveling the symmetries of quantum theory of gravity.

Einstein’s general theory of relativity, which describes gravity, is a classical theory. In everyday life, where gravitational force is very weak general theory of relativity works wonderfully and has made enormous number of predictions about the large-scale structure of the universe, which have been experimentally verified. However, at very short distances of the order of 10^{−35} m, for example, in case of sizes far smaller than the atomic nucleus, classical theory of gravity breaks down. This is because quantum fluctuations in the space-time geometry become important.

So a broader framework is necessary. But it is very unlikely that the standard model of elementary particle physics, which is a quantum theory, can be successfully merged with a theory of gravity which is classical. So gravity needs to be quantized.

Theories which describe our four-dimensional world are also formulated in four dimensions. An example is the equations of general theory of relativity. However, there are strong indications that the equations of the quantum theory of gravity should be formulated on a three-dimensional space-time which can be thought of as the boundary of our four-dimensional world. This type of description is called Holographic.

One of the most surprising facts about this description is that there is no gravity in the three-dimensional world where the equations of quantum gravity are formulated. The understanding of the three-dimensional theory, which describes quantum gravity in four dimensions, is still in its infancy. Through the SwarnaJayanti Fellowship supported by the Department of Science and Technology, Professor Banerjee seeks to understand the complete set of symmetries of this theory and the equations of this three-dimensional theory.

Jacob Bekenstein and Stephen Hawking discovered in seventies that black holes are thermodynamic systems with temperature, entropy, and so on. But classical gravity cannot explain the thermodynamic nature of black holes. The understanding of the quantum theory of gravity may lead to an understanding and computation of the entropy of general black holes. This will be a major breakthrough in our understanding of gravity.

*For more details, Shamik Banerjee** (bshamik[at]iopb[dot]res[dot]in)** can be contacted.*