Null Surfaces, Boundary Variations and Thermodynamics

by Sumanta Chakraborty (School of Physical Sciences, Indian Association for the Cultivation of Science (IACS))

MPP Main/2-313 - 313 (Main) (Zoom)

MPP Main/2-313 - 313 (Main)


In this talk, I will discuss the variation of the gravitational action with null boundaries. In particular, I will demonstrate the null boundary term, which needs to be added to the gravitational action to make it well-posed. The same conclusion will also be arrived at using the Weiss variation as well. I will also demonstrate that this result transcends general relativity. Finally, I will connect up the null boundary term with thermodynamics and shall argue for a modified action principle from which Einstein's equations with a positive cosmological constant can be arrived at.