Glenn Barnich (Free University of Brussels & International Solvay Institutes) & Ven Chandrasekaran (UC Berkeley)


Tuesday, April 16, 2019, 1:30pm to 2:30pm


BHI conference Room: 20 Garden Street, Cambridge (Lunch will be served at 1:00 pm)

Glenn Barnich (Free University of Brussels & International Solvay Institutes)

Title : Charged black body radiation

Abstract: The semiclassical contribution to the partition function is obtained by evaluating the Euclidean action
improved through suitable boundary terms. We address the question of which degrees of freedom are
responsible for this contribution. A physical toy model for the gravitational problem is a charged vacuum
capacitor. For a planar charged vacuum capacitor with perfectly conducting plates, we identify the degrees of freedom that, in the quantum theory,
give rise to additional contributions to the standard blackbody result proportional to the area of the plates
and that allow for a microscopic derivation of the thermodynamics of the charged capacitor.


Ven Chandrasekaran (UC Berkeley)

Title: Symmetries and charges of general relativity at null boundaries

Abstract: Boundaries in gauge theory and gravity have a rich structure that can provide insights into the underlying theory. Null boundaries are particularly important due to the fundamental role played by black holes, null infinity, and causal diamonds. In this talk I will study general relativity at a null boundary using the covariant phase space formalism. I will show that the symmetry algebra of general relativity at any null boundary is the semi-direct sum of diffeomorphisms on the two sphere and a nonabelian algebra of supertranslations. I will find the charges of this algebra at cross sections of the null surface as well as the associated fluxes. Throughout I will compare with the BMS algebra/charges at null infinity. I will also derive the generators of the symmetries for event horizons, and comment on the relation to black hole soft hair.