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Quantum Gravity

This series consists of talks in the area of Quantum Gravity.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

Fermi's lazy photon, the GEO600 anomaly, and the no-Riemann-no-pie theorem

Submitted by Anonymous on November 3, 2012 - 9:37pm
Wednesday Mar 25, 2009
Speaker(s): 
Giovanni Amelino-Camelia

I comment on rather significant recent developments that are relevant for proposals I had presented in previous PI seminars. The Fermi/GLAST space telescope has reported observations that would naturally fit previous formalizations of Planck-scale-induced in-vacuo dispersion (but also quite a few other things). And the unexplained excess noise found at the GEO600 interferometer is just of the type that had been previously described in terms of phenomenological models of spacetime foam (but may well be caused by quite a few other things).

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Graviton propagator from EPRL spinfoam model

Submitted by Anonymous on November 3, 2012 - 9:37pm
Wednesday Feb 11, 2009
Speaker(s): 
Claudio Perini

We derive geometric correlation functions in the new spinfoam model with coherent states techniques, making connection with quantum Regge calculus and perturbative quantum gravity. In particular we recover the expected scaling with distance for all components of the propagator. We expect the same technique to be well-suited for other spinfoam models.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

GR/EFT and Black Hole dynamics

Submitted by Anonymous on November 3, 2012 - 9:37pm
Wednesday Jan 28, 2009
Speaker(s): 
Rafael Porto

In this talk I will review how ideas borrowed from perturbative Quantum Gravity and Effective Field Theory (EFT) in Particle Physics can be applied to problems in General Relativity (GR), such as calculating gravitational wave emission by inspiralling spinning binary systems, including finite size effects and absorption. I will discuss in somewhat more detail how to account for dissipative effects, where the GR/EFT duality is used to predict the power loss due to absorption in the dynamics of binary spinning Black Holes.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Topos formulation of Consistent Histories

Submitted by Anonymous on November 3, 2012 - 9:37pm
Wednesday Jan 14, 2009
Speaker(s): 
Cecilia Flori

In this talk I will describe a topos formulation of consistent histories obtained using the topos reformulation of standard quantum mechanics put forward by Doering and Isham. Such a reformulation leads to a novel type of logic with which to represent propositions. In the first part of the talk I will introduce the topos reformulation of quantum mechanics. I will then explain how such a reformulation can be extended so as to include temporally-ordered collection of propositions as opposed to single time propositions.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Constraint free canonical GR using characteristic data

Submitted by Anonymous on November 3, 2012 - 9:37pm
Thursday Dec 18, 2008
Speaker(s): 
Michael Reisenberger

The handling of the constraints on initial data is a major issue in most canonical formulations of general relativity. Since the 1960s unconstrained initial data for GR that living on null hypersurfaces has been known, but no canoncial formulation based on these data was developed due to conceptual and technical difficulties. I will explain how these dificulties have been overcome and outline the resulting canonical framework.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Why there is no information loss

Submitted by Anonymous on November 3, 2012 - 9:37pm
Thursday Dec 04, 2008
Speaker(s): 
Abhay Ashtekar

Using 2-dimensional CGHS black holes, I will argue that information is not lost in the Hawking evaporation because the quantum space-time is significantly larger than the classical one. I will begin with a discussion of the conceptual underpinnings of problem and then introduce a general, non-perturbative framework to describe quantum CGHS black holes. I will show that the Hawking effect emerges from it in the first approximation.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Cosmic Ray experiments and Lorentz Invariance Violations.

Submitted by Anonymous on November 3, 2012 - 9:37pm
Thursday Nov 27, 2008
Speaker(s): 
Aurelio Grillo

As well known, cosmic ray experiments can put strong constraints on possible Lorentz Invariance Violations. In particular, the presence of the so called GZK \'cut-off\' may indicate that protons do propagate in the Universe as expected from relativistic invariance. The presence of this feature in the spectrum has been convincingly indicated by the HiRes and Auger experiments, while the Auger Observatory has given indication on the correlation of Ultra High Energy Cosmic particles with nearby sources, as predicted by the GZK feature.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Computing Black Hole entropy in LQG from a CFT perspective

Submitted by Anonymous on November 3, 2012 - 9:37pm
Wednesday Nov 26, 2008
Speaker(s): 
iagullo

Motivated by the analogy proposed by Witten between Chern-Simons theories and CFT-Wess-Zumino-Witten models, we explore a new way of computing the entropy of a black hole starting from the isolated horizon framework in Loop Quantum Gravity. The results seem to indicate that this analogy can work in this particular case. This could be a good starting point for the search of a deeper connection between the description of black holes in LQG and a conformal field theory.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Curved space, monsters and black hole entropy

Submitted by Anonymous on November 3, 2012 - 9:37pm
Thursday Nov 20, 2008
Speaker(s): 
Stephen Hsu

I discuss a class of compact objects (\'monsters\') with more entropy than a black hole of the same ADM mass. Such objects are problematic for AdS/CFT duality and the conventional interpretation of black hole entropy as counting of microstates. Nevertheless, monster initial data can be constructed in semi-classical general relativity without requiring large curvatures or energy densities.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

Finite States in Four Dimensional Quantized Gravity

Submitted by Anonymous on November 3, 2012 - 9:37pm
Thursday Nov 13, 2008
Speaker(s): 
Eyo Ita

The semiclassical-quantum correspondence (SQC) is a new principle which has enabled the explicit solution of the quantum constraints of GR in the full theory in the Ashtekar variables for gravity coupled to matter. The solutions, which constitute the physical space of states implementing the quantum dynamics of GR in the Dirac procedure, include a special class of states known as the generalized Kodama states (GKod). The GKodS can be seen as an analogue of the pure Kodama state (Kod) when quantum gravity (QGRA) is coupled to matter fields quantized on the same footing.

Collection/Series: 
Quantum Gravity
Scientific Areas: 
Quantum Gravity

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