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Sep
10
comment What is the geometry behind special relativity?
@Qmechanic: it is common to use "Lorentzian geometry" to refer to just the SR case. To pick any random reference: for instance first paragraph of Graciela S. Birman and Katsumi Nomizu, "Trigonometry in Lorentzian Geometry" The American Mathematical Monthly Vol. 91, No. 9 (Nov., 1984), pp. 543-549 jstor.org/stable/2323737
Sep
10
answered What is the geometry behind special relativity?
Sep
7
comment Is there any relationship between Gravity and Electromagnetism?
@DImension10, thanks for the feedback. I just went through that entry again and expanded a bit more here and there. For instance the Examples-section now has a new subsection "Cascades of KK-reductions from holographic boundaries" ncatlab.org/nlab/show/… .
Sep
4
comment Is there any relationship between Gravity and Electromagnetism?
ncatlab.org/nlab/show/Kaluza-Klein+mechanism
Sep
2
comment Calabi-Yau manifolds and compactification of extra dimensions in M-theory
See on the nLab at ncatlab.org/nlab/show/M-theory+on+G2-manifolds
Sep
2
awarded  Announcer
Sep
1
comment What are the details of the renormalization of Chern-Simons theory?
Not sure what you mean. (Out of date?? And of course there is Chern-Simons in the book, see the explicit links above.) But let's leave it at that. Maybe somebody else has what you are after.
Sep
1
comment What are the details of the renormalization of Chern-Simons theory?
John, maybe renormalization as such is not for beginners? I think Costello's account is about the best that there is. A beginner might take it as incentive to study and learn more and eventually cease to be a beginner and become an expert.
Aug
31
answered Why quantum mechanics?
Aug
30
answered Why one-dimensional strings, but not higher-dimensional shells/membranes?
Aug
30
comment Why one-dimensional strings, but not higher-dimensional shells/membranes?
More commented references on membrane/M2-brane physics are here: ncatlab.org/nlab/show/M2-brane
Aug
29
revised What are the details of the renormalization of Chern-Simons theory?
added 196 characters in body
Aug
29
answered What are the details of the renormalization of Chern-Simons theory?
Aug
28
awarded  Nice Question
Aug
28
comment What is Mathematical formulation of entropic Gravitational force?
...is another question. And an ill-defined one, to my mind.
Aug
28
comment What is Mathematical formulation of entropic Gravitational force?
@Guest: what these replies are trying to say is that this idea is very vague and hence has no mathematical formulation. I wish it had a physical formulation. The best there is maybe is Ted Jacobson's derivation of the Einstein's equations from the assumption that horizon areas are proportonal to entropy and application of thermodynamic laws to this. See here: ncatlab.org/nlab/show/Bekenstein-Hawking+entropy#Jacobson95 This is a solid argument which, after one accepts the assumptions, should be mathematically rigorous. But if from that it follows that "gravity is an entropic force" is...
Aug
28
comment Is it possible all matter in the universe emerges from nothing?
+1 for trying to make people think more formally and phrase questions and answers more carefully, hence more scientifically.
Aug
27
comment Why does string theory have such a huge landscape?
I have now added a corresponding item to the nLab String Theory FAQ: ncatlab.org/nlab/show/…
Aug
27
revised Why does string theory have such a huge landscape?
added pointer to new FAQ entry
Aug
27
comment Why does string theory have such a huge landscape?
... is 10 per cycle, and 500 times a choice of 10, hence 10^500 choices. As you see, this number is hand-waving incarnate and the only information it carries is this: look, while there are finitely many of choices of internal flux, due to a charge quantization condition, on a typical Calabi-Yau there are still quite a few such choices.