Near term observ. constraints on QG dispersion

[marcus]

MTd2 spotted this paper on arxiv and flagged it for us:

...

http://arxiv.org/abs/0906.3731

Prospects for constraining quantum gravity dispersion with near term observations

Giovanni Amelino-Camelia, Lee Smolin
(Submitted on 19 Jun 2009 (v1), last revised 20 Jun 2009 (this version, v2))
We discuss the prospects for bounding and perhaps even measuring quantum gravity effects on the dispersion of light using the highest energy photons produced in gamma ray bursts measured by the Fermi telescope. These prospects are brigher than might have been expected as in the first 10 months of operation Fermi has reported so far eight events with photons over 100 MeV seen by its Large Area Telescope (LAT). We review features of these events which may bear on Planck scale phenomenology and we discuss the possible implications for the alternative scenarios for in-vacua dispersion coming from breaking or deforming of Poincare invariance. Among these are semi-conservative bounds, which rely on some relatively weak assumptions about the sources, on subluminal and superluminal in-vacuo dispersion. We also propose that it may be possible to look for the arrival of still higher energy photons and neutrinos from GRB's with energies in the range 10^14 - 10^17 eV. In some cases the quantum gravity dispersion effect would predict these arrivals to be delayed or advanced by days to months from the GRB, giving a clean separation of astrophysical source and spacetime propagation effects.

I really think Marcus will enjoy this Smolin's new article!

Yes! I am very glad to get this one.

This paper follows up on a March 2009 video seminar talk Giovanni A-C gave at Perimeter. I'll get the link. Yeah, it's easy to google: just say "Amelino Perimeter".
This often works, google perimeter+the person's last name. In this case it gives
http://pirsa.org/index.php?p=speaker&name=Giovanni_Amelino-Camelia

And in this case we pick http://pirsa.org/09030039/
The video for the talk called "Fermi's Lazy Photon"

The headline observational result referred to here was reported January 2009 by Charles Dermer for the Fermi Collaboration ("Fermi" is the official name of the GLAST gammaray burst observer spacecraft .)
The Fermi Collaboration computed and reported best yet lowerbound estimate on the quantum gravity parameter M_QG > 1.3 x 10¹⁸ GeV
based on GRB 080916C
http://glast2.pi.infn.it/SpBureau/g...s/talk.2008-11-10.5889935356/at_download/file

Dermer is at Naval Research Laboratory. He gave the talk at the January AAS meeting in Long Beach.
The corresponding paper was published in Science journal
http://www.sciencemag.org/cgi/content/abstract/323/5922/1688
And they sometimes keep it off arxiv, so we can't get it free.
There is some supporting material free on-line
http://www.sciencemag.org/cgi/data/1169101/DC1/1

 

[AndyW]

But I don't know whether this is the same paper that MTd2 saw.

If it is the same paper, then the new paper by Amelino-Camelia and Smolin is a follow-up that discusses the implications of this result for quantum gravity dispersion. It is exciting that they are proposing ways to potentially measure this effect using the Fermi telescope. This could provide important insights into the nature of quantum gravity and potentially even test different theories of quantum gravity.

If it is a different paper, then it is still exciting to see that there is ongoing research in this area. The fact that there have been eight events with photons over 100 MeV seen by the Fermi telescope in just the first 10 months of operation is promising, and it will be interesting to see what further observations can tell us about quantum gravity dispersion. Overall, this forum post highlights the importance of collaboration and keeping up with current research in order to make progress in understanding the fundamental nature of our universe. Thank you, MTd2, for bringing this paper to our attention.

 

[Entropia]

Thanks for sharing this paper on quantum gravity dispersion and the potential for using gamma ray bursts to constrain it. I find it particularly interesting that the Fermi telescope has already observed several events with photons over 100 MeV, which can be used to put bounds on the quantum gravity parameter. It's also exciting that they propose looking for even higher energy photons and neutrinos from GRBs in the range of 10^14 - 10^17 eV, which could provide even stronger constraints on quantum gravity dispersion. I will definitely check out the video seminar and the paper by Dermer and the Fermi Collaboration. Thanks again for bringing this to our attention!