Title: Probing Quantum Gravity using Photons from a Mkn 501 Flare Observed by MAGIC Authors: J. Albert, et al., for the MAGIC Collaboration, John Ellis, N.E. Mavromatos, D.V. Nanopoulos, A.S. Sakharov, E.K.G. Sarkisyan We use the timing of photons observed by the MAGIC gamma-ray telescope during a flare of the active galaxy Markarian 501 to probe a vacuum refractive index ~ 1-(E/M_QGn)^n, n = 1,2, that might be induced by quantum gravity. The peaking of the flare is found to maximise for quantum-gravity mass scales M_QG1 ~ 0.4x10^18 GeV or M_QG2 ~ 0.6x10^11 GeV, and we establish lower limits M_QG1 > 0.26x10^18 GeV or M_QG2 > 0.39x10^11 GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect. Read more (22kb, PDF)
Here, draqon, read all about it. Please Register or Log in to view the hidden image! http://en.wikipedia.org/wiki/Quantum_gravity
Read-Only...quantum theoretical physics. What sort of math do I need to learn in order to truly understand what is behind all the functions involved? obviously higher than multivariable calculus..
Sorry, draqon, I honestly don't know. I topped out at one year of calculus because that's when I moved heavily into business law and chemistry. Yeah, I know, that's a odd combination - but both eventually wound up serving me VERY well. Please Register or Log in to view the hidden image!
The paper is very interesting, but I fail to understand how it applies to the title of your thread, "M-theory test"? The paper supports the hypothesized dynamical nature of the vacuum, for which we have no current theory. I will try to briefly explain what that means below. I'll start with the Shapiro effect, the time delay of EM radiation moving through a gravitational field. It is well known that photons experience a time delay when they pass through a gravitational field, they take longer to arrive than if their was no gravitational field present. General Relativity explains this as the photons following a 'curvature' of spacetime caused by gravity. GR postulates that the photons follow a curved path in a gravity field that is longer than a straight path between two points, the (1) emission point and their (2) arrival point here on Earth. GR states, as does SR, that the speed of light is always 'c', that the longer path is the reason the photons arrive later than they should if no gravity was present (flat spacetime). What they measured in the paper suggests that the 'curved spacetime' model is incorrect, and that the flat spacetime of SR must be modified to model gravitational effects on the propogation of massless particles, photons. The reason the curved spacetime model is not exactly correct is because very high energy photons were delayed more than slightly lower energy photons, a difference of four minutes in their arrival times here on Earth. What was observed was, on July 9th for instance, a short duration flare that lasted between one and two minutes. Highly energetic photons from ranging 150GeV to 10TeV were emitted during the short duration flare. The photons in the 1.2-10 TeV energy band arrived four minutes later than the photons in the .25-.6 TeV energy band. If curved spacetime were accurate, both sets of photons would have arrived at the same time because both sets were emitted at the same time and followed the same path through the vacuum on their way to us here on Earth. So the conclusion is that light does not always travel at exactly 'c'. The speed of light slows when the photons move through a gravitational field and even photons of different energies vary slightly when travelling through gravity fields. The observation confirms what I have been arguing for quite some time here on sciforums.
draqon--- Learn the calculus well, and differential equations. Then you want to learn some differential geometry, some topology, and complex analysis.
inquisitive--- This guy Mavromatos just wrote a paper about getting Lorentz violations (which is what you described) out of string theory. I think this experiment COULD actually be significant because it is constraining the scale of quantum gravity, which is naively the planck scale, or 10^19 GeV.
2inquisitive: Thanks for the very readable summation, it was quite interesting. This appears in one sense similar to the varying retardation of visible light that travels through a medium, depending upon the frequency of the photons. Here, instead, the retardation varies depending on the frequency of the gamma photons, but the retardation is caused by a gravitational field through which the photons travel, not through a medium. Do you have any theoretical insight as to what's going on here? I've not seen your previous posts in which you've been arguing about this, and I'd appreciate a little more of your insight. Much obliged, Walter -------------
@2inquisitive yeah, if there was a recorded timing difference with the high-energy gammas rays, then some theories propose that that this is due to a `frothy` nature to spacetime. ie. The path of the photons would be bent by the small scale fluctuations in spacetime. It would need something as distant as quasars to show the accumulative effect of this froth. The `timing delay`/ `size of froth`, would constrain the physics of certain variants in string theory and loop quantum gravity.
