Planck scale Lorentz-symmetry test theories Amelino-Camelia

[marcus]

"Planck scale Lorentz-symmetry test theories" Amelino-Camelia

new paper by Giovanni A-C
http://arxiv.org/abs/astro-ph/0410076

 

[meteor]

I didn't know that the IR/UV mixing had any relation with noncommutative spacetimes. Interesting...

 

[marcus]

I didn't know that the IR/UV mixing had any relation with noncommutative spacetimes. Interesting...

I see the passage on page 6 which relates to your comment, but I don't know enough about noncommutative spacetimes to reply, meteor.

I think the strongest message in this paper is that he is taking actual test-models---a definite version of LQG, for example---to be tested by observation. he is making QG phenomenology less vague, upping the ante. And he points out how some previous published work that claimed to constrain QG modification of Lorentz symmetry was not actually valid or its implications were poorly understood by non-specialists.

I get a sense of the paper's thrust from the first paragraph of the closing remarks:

---exerpt Amelino-Camelia conclusions---
VI. CLOSING REMARKS

With this paper I am hoping to ignite a debate which should lead to the transition toward a more mature phase of quantum-gravity phenomenology, in which a key role is played by some reference test theories. I gave an explicit formulation of two test theories which could be considered for this role, and I discussed a few examples of phenomenological analyses with these two test theories. The two test theories assume basically the same type of modification of the dispersion relation, but in my illustrative examples of phenomenological analyses it emerged that the phenomenology is in some cases very different. This exposes the shortcomings of an approach to the phenomenology of Planck-scale modified dispersion relations which had become fashionable in the recent literature: there have been several papers claiming to improve limits on Planck-scale modifications of the dispersion relation, but the different studies were simply considering the same type of dispersion relation within significantly different test theories, or worse the phenomenological analysis did not even rely on a well-defined test theory. From outside the quantum-gravity phenomenology community these papers were actually perceived as a gradual improvement in the experimental bounds on the overall idea of Planck-scale departures from Lorentz symmetry, to the point that there is now a wide-spread perception that in general departures from Lorentz symmetry are already experimentally constrained to be far beyond the Planck-scale. Instead I showed that two simple and rather natural test theories evade automatically some of the possible opportunities for constraints.
---end quote---

like it or not, Amelino-Camelia is the (or one of the) world's leading expert(s) on QG phenomenology. This is his latest pronouncement. I guess I better quote the abstract too:

----abstract---
In the recent quantum-gravity literature there has been strong interest in the possibility of Planck-scale departures from Lorentz symmetry, including possible modifications of the energy/momentum dispersion relation. I stress that a meaningful characterization of the progress of experimental bounds on these Planck-scale effects requires the analysis of some reference test theories, and I propose to focus on two "minimal'' test theories, a pure-kinematics test theory and an effective-field-theory-based test theory. I illustrate some features of the phenomenology based on these test theories considering some popular strategies for constraining Planck-scale effects, and in particular I observe that sensitivities that are already in the Planck-scale range for some parameters of the two test theories can be achieved using observations of TeV photons from Blazars, both using the so-called "gamma-ray time-of-flight analyses'' and using the now robust evidence of absorption of TeV photons. Instead the Crab-nebula synchrotron-radiation analyses, whose preliminary sensitivity estimates raised high hopes, actually do not lead to any bound on the parameters of the two "minimal'' test theories. The Crab-nebula synchrotron-radiation analyses do however constrain some possible generalizations of one of the minimal test theories. As an example of forthcoming data which could provide extremely stringent (beyond-Planckian) limits on the two minimal test theories I consider the possibility of studies of the GZK cutoff for cosmic-rays.
---end quote---