School of Physics and Astronomy

Gravity: the emergent perspective

26 March 2014

Time: 4:30pm
Venue: Maths 103

The London Relativity and Cosmology Seminar
Thanu Padmanabhan (IUCA , India)

There is sufficient amount of internal evidence in the nature of gravitational theories to indicate that gravity is an emergent phenomenon with its field equations having the same conceptual status as, for example, the equations of elasticity or fluid mechanics. Further, the gravitational dynamics in a bulk region of space can be connected to a thermodynamic description in the boundary of that region. This `holographic' feature allows us to understand the nature of gravity from an alternative perspective. In particular, I will show that the time evolution of spacetime is driven by the difference between the number of degrees of freedom in the bulk and in the boundary of a region. All static spacetimes, therefore, are in holographic equipartition, with the number of degrees of freedom in the boundary being equal to the number of degrees of freedom in the bulk. The approach also allows us to obtain the gravitational field equations from a thermodynamic variational principle, which -- in turn -- is required to solve the cosmological constant problem. I will describe several aspects of this paradigm.