Photons and Quantum Gravity in Astrophysics Speaker(s): Alfio Bonanno, Robert Brandenberger, Joao Magueijo, Robert Nemiroff, Niayesh Afshordi, Giovanni AmelinoCamelia
Abstract: Asymptotically safe inflation and CMB polarization
The presence of complex critical exponents in the scaling behavior of the Newton constant and Cosmological constant has dramatic consequences at the inflation scale. In particular an infinite number of unstable deSitter vacua emerges from an effective quantum gravitational action. In this framework, the possibility of detecting specific signaturesof a nongaussian fixed point of the gravitational interactions in the CMB polarization spectrum will then be discussed. ________________________ Cosmological windows such as CMB polarization and 21cm redshift surveys to probe Planckscale physics ________________________ Quantum gravity and a chiral signature in gravity waves I show how quantum gravity could lead to a chiral signature in the graviational wave background, proportional to the imaginary part of the Immirzi parameter. This would leave a distinctive imprint in the polarization of the cosmic microwave background. I will discuss how this isue is closely related to that of identifying the ground of base state for quantum gravity. _______________________ A Possible Bound on Spectral Dispersion from FermiDetected Gamma Ray Burst 090510A Three photons spanning about 30 GeV arrived within about one millisecond from the Fermidetected GRB 090510A at a redshift of about 0.9. Although conceivably a > 3Ïƒ statistical fluctuation when taken at face value this photon bunch  quite possibly a classic GRB pulse  leads to a relatively tight bound on the ability of our universe to disperse high energy photons. Specifically given a generic dispersion relation where the time delay is proportional to the photon energy to the first power the limit on the dispersion strength is k1 < 1.61Ã—105 sec Gpc1 GeV1. In the context of some theories of quantum gravity this conservative bound translates into an minimum energy scale greater than 525 m_Planck suggesting that spacetime is smooth at energies perhaps three orders of magnitude over the Planck mass. Date: 22/10/2012  4:30 pm
Collection: Experimental Search for Quantum Gravity 2012
