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These are models that extend/modify the theory of general relativity: In theoretical physics, massive gravity is a theory of gravity that modifies general relativity by endowing the graviton with a nonzero mass. In the classical theory, this means that gravitational waves obey a massive wave equation and hence travel at speeds below the speed of light. ...


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There is a recent survey of canonical quantum gravity and its confrontation with exciting experimental data: R.P. Woodard, Perturbative Quantum Gravity Comes of Age, Int. J. Modern Physics D 23 (2014), 1430020. http://arxiv.org/abs/1407.4748. Woodard writes in the introduction: All of the problems that had to be solved for flat space scattering ...


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You are asking if one of these theories is "more correct" than the other. That is a somewhat philosophical question. You can surely believe that a theory "makes more sense" than another, but this has more to do with your personal preference. Correctness in modern science is a matter of agreement with experimental observation. And at the moment there is no ...


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The abstract for your third reference has a Particle Data Group block which gives $J=0$, but without much confidence. A footnote on page 5 of that reference expresses skepticism that it's a graviton. I'm afraid you're not going to get much more "updated" information than a preprint from six weeks ago. The experiment is still going on.


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String theory does not say that GR or quantum field theory hold at those scales. It posits strings, and gets to the Planck scale and predicts what it might look like, foam or stringy things arising and changing and so on. At lower energies it is consistent with quantum field theory and GR. So, GR is a low energy description, and does not worry about the ...


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You can show within Newtonian gravitation that the net gravitational force at the center of a continuous mass distribution with a nontrivial point group symmetry is zero. (If the body doesn't have a point group symmetry then there's no clear notion of a "center".) Black holes fail to satisfy two of these conditions - they're not Newtonian and the mass ...


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If you really want to learn Quantum Gravity it is never too late to introduce yourself to General Relativity as well as Quantum Field Theory. First one is crucial for understanding Quantum Gravity because it is based on both QM and GR. So for more advanced studying I recommend this book http://www.cpt.univ-mrs.fr/~rovelli/book.pdf


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This question is really broad, so I'll just give a quick summary. Quantum Gravity: This is a field of theoretical physics that attempts to reconcile general relativity and quantum mechanics. While the hope is to give a theory of gravity that works on the quantum level, the equations one gets cannot be renormalized, which makes them unable to predict ...



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