Talk detail

Participant	Ashtekar, Abhay
Institution	Institute for Grvitation and the Cosmos, Penn State - 104 Davey - University Park - PA - USA

Session	PS	Accepted		Order	Time
Talk	Oral abstract	Title	Loop Quantum Gravity
Coauthors
Abstract	The goal of this talk is to provide a broad overview of foundations and applications of Loop Quantum Gravity. Over the last 5 years or so the subject has matured sufficiently to create an active dialog between theory and observations. In particular, contrary to a common belief, Planck scale dynamics can lead to observable effects even in inflationary scenarios and, in turn, observations can inform loop quantum gravity about viable initial conditions. Through such examples, the talk will provide a feel for the current status of the field.
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Session	EU2	Accepted		Order	Time
Talk	Oral abstract	Title	Singularity resolution in Loop Quantum Cosmology
Coauthors
Abstract	Quantum Riemannian geometry underlying Loop Quantum Gravity modifies the geometrical left hand side of Einstein's equations. While these modifications are completely negligible if the space-time curvature is below a thousandth of the Planck curvature, they increase extremely rapidly in the Planck regime. The net effect is a repulsive force that overwhelms the classical attraction and naturally leads to a resolution of cosmological singularities. This effect has been analyzed using Hamiltonian, path integral and decoherent histories approach. In cosmological models, all strong curvature singularities are resolved, including those in the Bianchi space-times. In view of the Belinskii-Lifshitz-Khalatnikov conjecture in classical general relativity, this is an indication that the quantum geometry effects underlying Loop Quantum Gravity may resolve all spacelike singularities of general relativity.
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Session	BH6	Accepted		Order	Time
Talk	Oral abstract	Title	Quantum Black holes and Unitarity
Coauthors
Abstract	There is ample evidence that, because of the singularity resolution, quantum space-times can be vastly larger than what classical general relativity would lead us to believe. Thanks to this enlargement, unitarity can be restored in the evaporation of black holes. There is no event horizon; what forms in the collapse and evaporates is the dynamical horizon. Because of the absence of an event horizon, we are not confronted with firewalls. Finally, in contrast to ADS/CFT, these arguments deal with the evaporation process directly in the physical space-time.
Pdf file

Session	QG3	Accepted		Order	Time
Talk	Oral abstract	Title	Overview of Recent Applictions of Loop Quantum Gravity to Cosmology
Coauthors
Abstract	I will provide an overview of recent applications of Loop Quantum Gravity to Cosmology. Specifically, Loop Quantum Cosmology has extended the standard cosmological perturbation theory over the 12 orders of magnitude in curvature and matter density that separate the onset of inflation from the Planck regime. This extension has brought out an unforeseen interplay between the quantum geometry effects in the deep ultraviolet that are resolve the big bang singularity, and properties of perturbations in the infrared that affect physics at the largest angular scales. In particular, they open a door to account for the `anomalies' in the Planck data using fundamental physics of quantum gravity. These advances illustrate, in concrete terms, that the subject has matured sufficiently to allow a two way dialog between theory and observations. This talk will complement and bridge the brief summary of Loop Quantum Gravity in my plenary talk and the detailed account of the resolution of cosmological singularities, that I will provide in Session EU2 on Thursday, entitled "Quantum Fields", Chaired by Prof Belinski.
Pdf file