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Jul
1
comment Significance for LQG of Sen's result on entropy of black holes?
LQG has spun off a large number of different models, none of which have gone very far towards recovering the classical limit. So any predictions made at any stage of the research program are not robust, and therefore it can keep coming back.
Jun
29
comment Map of the gravitational strength of the solar system
Perhaps if you wrote to someone like John Walker, programmer of fourmilab.ch/solar ... he might be able to add it as a feature.
Jun
29
comment Map of the gravitational strength of the solar system
"I just want a kind of snapshot" But the planets are in constant motion... Do you want a solar system simulator (virtual orrery) overlaid with the combination of all the gravitational fields?
Jun
28
comment What is the most natural new physics one can expect at the TeV scale: new (supersymmetric)particles or some new (non-commutative) spacetime structure?
I've looked through the NCG-physics literature, old and new, and it's claimed that their dilaton solution to the hierarchy problem works in the same way as the Randall-Sundrum model, where a small number (distance between the two branes, in the case of RS) serves as an exponent and produces the large difference between weak scale (Fermi scale) and GUT/Planck scale. The analogy with RS is said to be quite close. I can't judge it for myself yet.
Jun
28
comment What are the implications of the Nesvizhevsky experiment and followup experiments with ultracold neutrons?
Entropic gravity has a very specific problem - it says the number of fundamental states of a quantum object in a gravitational field should increase exponentially with height. That should screw up completely basic quantum behaviors like interference of waves, because the waves should get "lost" in the increasing state space and have no chance of finding each other in order to recombine - this is in Kobakhidze.
Jun
28
comment What are the implications of the Nesvizhevsky experiment and followup experiments with ultracold neutrons?
Earlier you said "they demonstrate that gravity has an effect on the quantum level", and later "The results show that gravity is not an emergent property". The problem with these statements is that you can write equations for "quantum mechanics in a classical gravitational field" and that is all you need to explain the results. The only way this would be evidence against a theory of emergent gravity, is if the theory said that no gravitational forces at all should exist on microscopic scales, and I don't know if any serious theories say that...
Jun
28
comment What are the implications of the Nesvizhevsky experiment and followup experiments with ultracold neutrons?
(I should add for readers that "Yukawa forces" here refers to a Yukawa-like force appearing in theories with large extra dimensions, not the nuclear forces of the standard model.)
Jun
28
comment What are the implications of the Nesvizhevsky experiment and followup experiments with ultracold neutrons?
Apparently I didn't follow your links, because now I look at them, I can see why you are saying things that sounded like total confusion... You say: "the experimental data shows evidence for Yukawa forces as well as the possibility of a new kind of interaction in nature". No, those papers are saying that such experiments might be able to detect such things if they exist. But there's no evidence that they exist.
Jun
28
comment 115 GeV, 170 GeV, and the noncommutative standard model
One issue which deserves to be examined, is whether the Higgs mass is technically natural, in the extension. I will think about this, in connection with the other question physics.stackexchange.com/q/69176/1486
Jun
28
comment 115 GeV, 170 GeV, and the noncommutative standard model
In the extension with the second scalar, the range of plausible mass values is shifted lower, so the experimental value is somewhere in the middle of the new range. It deserves to be mentioned, but Estrada and Marcolli is closer to what I wanted...
Jun
28
comment 115 GeV, 170 GeV, and the noncommutative standard model
In my question, I was looking for a physical mechanism which would force the Higgs mass to lie at the edge of its allowed range. Estrada and Marcolli arxiv.org/abs/1208.5023 achieved something like this, by adding the assumption of asymptotic safety arxiv.org/abs/0912.0208 to the noncommutative SM...
Jun
27
comment Is the Mendeleev table explained in quantum mechanics?
How do you define the Mendeleev table? i.e. what propositions do you want to see derived?
Jun
26
answered Has Voyager 1 entered a solar radiation belt?
Jun
26
comment What is the most natural new physics one can expect at the TeV scale: new (supersymmetric)particles or some new (non-commutative) spacetime structure?
There actually is a question - it's the part in bold.
Jun
25
comment What is the most natural new physics one can expect at the TeV scale: new (supersymmetric)particles or some new (non-commutative) spacetime structure?
As far as I know, the noncommutative standard model still has a hierarchy problem; it doesn't predict the electroweak scale, it just constrains the possible masses of the Higgs, after many other SM parameters are specified.
Jun
25
comment Since when were Loop Quantum Gravity (LQG) and Einstein-Cartan (EC) theories experimentally proven?
@Dilaton I would class F-theory as a part of Type IIB. Unlike the extra dimension of M-theory, the extra two dimensions of F-theory never become large and physical. For now it's just a formalism. Also F and M are connected by dualities.
Jun
25
comment Since when were Loop Quantum Gravity (LQG) and Einstein-Cartan (EC) theories experimentally proven?
I disagree, because why not then have links also to heterotic string theory, bosonic string theory... But Wikipedia is the proper place for this discussion.
Jun
25
comment Since when were Loop Quantum Gravity (LQG) and Einstein-Cartan (EC) theories experimentally proven?
If you look at the template's edit history, these classifications (and this system of categories) were introduced by one user, "Teply", who thought the previous version was too wishy-washy, and who (on the talk page) asked people to correct it, if it contained errors. But no-one has done so.
Jun
20
awarded  Nice Answer
Jun
19
comment What are the implications of the Nesvizhevsky experiment and followup experiments with ultracold neutrons?
@Mr X, the experiments had nothing to do with any of that. They were just about energy levels. A nucleus has a charge and creates an electromagnetic potential, and electrons in that potential can occupy different energy levels. Here there were neutrons in a gravitational potential and they also had quantized energy levels. But the potential itself was not treated in a quantized way, as it would be in quantum field theory. There is nothing here about gravitons or new interactions, just the behavior of neutron wavefunctions in gravity.