Midisuperspace Laboratories for Loop Quantum Gravity

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The study of how black holes evaporate is perhaps the most important outstanding problem in theoretical physics today. It requires understanding the behavior of two of the pillars of modern physics, gravity and quantum field theory, in their most extreme regimes. Understanding how physical theories fit together in challenging regimes has in the past led to insights of spectacular consequences. An example of this could be Maxwell understanding how electricity and magnetism fit together led to the discovery of radio waves, with the ensuing transformational changes they induced in our society. A second very important objective of this type of work is the formation of human resources of very high quality. Physicists trained in these disciplines have proved valuable in industry and in finance. The PI will continue the outreach activities via the International Loop Quantum Gravity Seminar and the Loop Quantum Gravity Portal and its blogs for the general public. The application of techniques of loop quantum gravity in spherically symmetric contexts with the ultimate goal of understanding black hole evaporation will continue. Among the topics to be considered are: A) The study the applicability of the weak gravity conjecture in loop quantum gravity. This conjecture states that theories that do not make gravity the weakest interaction may lead to naked singularities. Loop quantum gravity eliminates singularities and therefore could bypass the negative consequences of the conjecture. B) Models of black hole evaporation in which the Hawking radiation is modeled via matter fields. These models have not been studied up to now in the context of loop quantum gravity. C) Extend our previous study of criticality in the collapse of scalar fields in loop quantum gravity to probe what happens close to where the singularity is in the classical theory. D) The treatment of axisymmetric space-times in loop quantum gravity proposed by the group will be further analyzed to probe if the singularity is eliminated in such cases as it is in spherical symmetry. E) Investigations in the formulation of gravity in terms of observables first proposed by Mandelstam in the 1960’s, which faced an obstacle in its development the groups was able to remove recently.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.