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marcus
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#296
Feb2-12, 04:23 PM
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Phenomenology issues affecting various models, which may already be ruled out, are part of the general QG phenomenology picture http://backreaction.blogspot.com/201...time-foam.html that we need to keep track of.
Although the observations discussed here seem not relevant to LQG specifically. In LQG space is not in a simple or naive sense "grainy". Its network states are quantum states of geometry (i.e. refer to relations among geometric measurements)---they're not imagined to be "what space is made of". Lorentz violation such as energydependent speed of light or the blurring of images one might get with a grainy substance are not predictions. One way to say it is QG is not about what space IS but rather it is about HOW IT RESPONDS to measurement. Analogous to basic quantum theory in other areas.

==quote Bee, above link==
...the authors have presented an analysis of the images of 157 high-redshift (z > 4) quasi-stellar objects. They found no blurring. With that, also the holographic foam model is ruled out. Or, to be precise, the parameter α is constrained into a range that is implausible for quantum gravitational effects.

As it is often the case in the phenomenology of quantum gravity, the plausible models are difficult, if not impossible, to constrain by data. And the implausible ones nobody misses when they are ruled out. This is a case of the latter.
==endquote==