What can Classical Gravity tell us about Quantum Structure of Spacetime?

Thanu Padmanabhan

Given the fact that several technical attempts to combine the principles of general relativity and quantum theory have not borne fruit, a fresh look at the conceptual aspects of this task becomes relevant.

Theoretical evidence of different nature, accumulated in the recent years, indicates a new perspective on gravity. The fact that spacetimes - like e.g., gaseous systems - can exhibit thermal phenomena suggests: (i) the existence of microstructure to spacetime and (ii) that gravity is an emergent phenomenon, like gas dynamics. This approach is similar to the one taken by Boltzmann, who could argue for the existence of molecules of gas, based essentially on the fact that a gas exhibits thermal phenomenon. I will show that many features of classical gravity, arising in a wide class of theories - including, but not limited to, standard Einstein's theory - admit a purely thermodynamic interpretation and reinforce the idea that gravity is an emergent phenomenon. This perspective provides us with a `top-down' view of the quantum structure of spacetime and there are interesting lessons to be learnt from these features and the analogy.

I will describe the necessary background, key results and their implications in a manner understandable to the non-experts in the audience.