Conveners
Tuesday Plenary Session: Block 3 - Black holes and the Quantum
- Abhay Ashtekar (Institute fro Gravitation & the Cosmos, Penn State)
Description
Tuesday plenary session
One of the surprising properties of black holes is that they can be assigned an entropy proportional to the area of the horizon. With this assignment, black holes obey the laws of thermodynamics.
Over the last decade, a new type of black hole entropy entropy formula was developed which is believed to give the von Neumann or fine grained entropy of the black hole. It is also a formula...
Hawking showed that the von Neumann or fine-grained entropy of the radiation emanating from an evaporating black hole monotonically increases throughout the black hole’s lifetime. This suggests that black hole formation and evaporation can evolve a pure quantum state of a collapsing star into a mixed quantum state of the Hawking radiation. This is in direct conflict with the unitarily of time...
In using QFT to study black holes, coordinate transformations are needed with boundary conditions at the horizons. To avoid quantum copies it is imperative that the mapping must be one-to-one. It is explained why this turns the horizons into projective spheres instead of regular spheres. Also what is needed is the concept of `antivacuum', a state on which all creation operators vanish. This...
I will review recent progress on our understanding of the issue of strong cosmic censorship in general relativity, including very recent developments in the case of non-zero cosmological constant.
I will talk about my very recent result in collaboration with Jeremie Szeftel in which we provide a complete proof of the nonlinear stability of the family of Kerr spacetimes Kerr(a, m) with small a/m. The proof, which builds on our previous work `` Global non-linear stability of Schwarzschild space under polarized perturbations’’ , introduces various new geometric and...
Singularity theorems of Penrose and Hawking are based on geodesic incompleteness. Physically, this criterion refers to the fate of classical test particles. What if one uses quantum fields instead? They would be more fundamental probes. For technical simplicity, I will restrict myself to cosmological singularities and show that one can unambiguously evolve quantum
fields across them in a...
I will discuss two complementary ways that one can address the quantum nature of radiation fields, with special reference to gravitational radiation. One, based on the Feynman-Vernon influence functional, is in principle complete, but challenging to work out fully. The second, based on minimal modeling of space-time and quantum theory, is extremely tractable, and sheds considerable light on...
