
#1
Dec1903, 10:04 AM

Astronomy
Sci Advisor
PF Gold
P: 22,809

the most recent LV paper I know of was just revised and reposted 18 December 2003
http://arxiv.org./abs/astroph/0309681 F. Stecker is one of the coauthors. "New limits on Planck scale Lorentz violation in QED" T. Jacobson, S. Liberati, D. Mattingly, F.W. Stecker Nereid recently recommended an earlier paper by Stecker (solo) http://arxiv.org./abs/astroph/0308214 "Constraints on Lorentz Invariance Violating Quantum Gravity and Large Extra Dimensions Models using High Energy Gamma Ray Observations" Stecker is at NASA Goddard, and the other three authors are at nearby U. Maryland. All have written several papers on tests of LV, Jacobson especiallyit's a longstanding interest of his I believe. Stecker has a review paper on highenergy cosmic rays which touches on tests of Lorentz violation among other topics "Cosmic Physics: The High Energy Frontier" http://arxiv.org./abs/astroph/0309027 However the most recent thing we have is, I think, the one I just mentioned by Jacobson, Mattingly, Liberati, Stecker. It was revised and reposted yesterday and is worth checking outhere's an exerpt: "Constraints on possible Lorentz symmetry violation (LV) of order E/MPlanck for electrons and photons in the framework of effective field theory (EFT) are discussed. Using (i) the report of polarized MeV emission from GRB021206 and (ii) the absence of vacuum ¡Cerenkov radiation from synchrotron electrons in the Crab nebula, we improve previous bounds by 10−10 and 10−2 respectively.... ...While no current suggestion of LV is firm enough to be considered a prediction, there is nevertheless great interest in the possibility of LV induced by Planck scale physics since it offers the hope of an observational window into quantum gravity... ...We use the reported observation [9] of polarized gamma rays from the gamma ray burst GRB021206 to improve the birefringence constraint by ten orders of magnitude.1 By consideration of the vacuum ¡Cerenkov process for the electrons producing the highest frequency synchrotron radiation from the Crab nebula we improve on the old birefringence constraint by two orders of magnitude... ...We adopt the framework of effective field theory as developed e.g. in [1, 2, 3], focusing on the electronphoton sector since this involves no other particles and there are many observations allowing a number of independent constraints to be combined. We assume rotational symmetry is preserved in a preferred frame, which is taken to coincide with that of the cosmic microwave background..." I've added the bolding for emphasis. Another useful reference is a Jacobson Liberati Mattingly paper revised and reposted 29 August 2003 "A strong astrophysical constraint on the violation of special relativity by quantum gravity" http://arxiv.org./abs/astroph/0212190 Qualitatively it seems that Stecker and the later papers are doing very much the same thing as this paper only making the constraints progressively tighter. So looking at this paper (which spells things out in considerable detail) can help understand this line of research. Here is an exerpt: "...Here we determine a very strong constraint on a type of Lorentz violation that produces a maximum electron speed less than the speed of light. We use the observation of 100 MeV synchrotron radiation from the Crab nebula..." 



#2
Dec1903, 10:17 AM

Astronomy
Sci Advisor
PF Gold
P: 22,809

the Stecker article that Nereid recommended just yesterday in
"Speed of light remains constant" thread is also a good indicator of where they are in LV research http://www.physicsforums.com/showthr...100#post117100 But that thread was originally not about LV but about timevarying speed of light, or so it seemed to me and David, another poster. So to consolidate the LV stuff into a single thread here is Nereid's and my reply: quote:  Originally posted by Nereid Found it! http://xxx.lanl.gov/abs/astroph/0308214 "Constraints on Lorentz Invariance Violating Quantum Gravity and Large Extra Dimensions Models using High Energy Gamma Ray Observations" Comments from people who read this paper are most welcome.  My reply essentially just points to the fact that Stecker seems to be talking about a situation where there is "a preferred inertial frame given by the cosmological rest frame of the cosmic microwave background radiation" This type of model was ruled out earlier by Smolin based on a previous paper by Jacobson, Liberati, Mattingly. Smolin strongly suggested back in March that models with a preferred frame are no longer in the running, at least in his view. As far as I know nothing Rovelli or Smolin talk about breaks Lorentz invariance in the sense of having a preferred frame. But this is what LV research is about (as the name "Lorentz violation" suggests.)  Here's a quote from the Stecker paper, page 6: "In many of these models Lorentz invariance is predicted to be violated at high energy. This results in interesting modifications of particle physics that are accesible to observational tests using TeV gammaray telescopes and cosmic ray detectors. An example of such a model is a quantum gravity model with a preferred inertial frame given by the cosmological rest frame of the cosmic microwave background radiation (For an extensive discussion, see the review given in Ref. [23].)" It might be helpful to consult the "review given in Ref. [23]" which Stecker offers as providing "an extensive discussion". Particularly pages 18 and 19 in that reference: section 4 The near term experimental situation. Here is the Ref. [23] link. Any comments? http://arxiv.org/hepth/0303185  



#3
Dec1903, 08:27 PM

Emeritus
PF Gold
P: 8,147

The KowalskiGlikman paper hepth/0304027 claims that showing a variable speed of light would disporve all DSR's since (they claim) all DSR's have a consttant speed of light, whatever their authors might think on the matter. Their attitude seems to be "We have been thinking about these κdeformed phase spaces for ten years, and you haven't.




#4
Dec1903, 10:46 PM

Astronomy
Sci Advisor
PF Gold
P: 22,809

tests of Lorentz violationI found his photo in the Karpasz Winterschool website and he looked ...well he did not look like a shy fellow. Actually I dont think he would have any trouble beating up Lee Smolin. He was wearing a black skijacket and turtleneck here's a link to his picture, judge for yourself http://www.ift.uni.wroc.pl/JKG/ 



#5
Dec2003, 04:49 PM

Emeritus
PF Gold
P: 8,147

Wonder what kind of motorcycle he rides.[:D]



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