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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


Dec
11
revised What does an atom radiate: a wave packet or a single photon?
added 9 characters in body; edited title; added 2 characters in body; edited tags; edited title
Dec
11
comment White Holes and Time-Reversed Oppenheimer-Snyder collapse
Yes, and the entropy of an egg is the same regardless of wether it comes before the chicken or after the chicken. But which evolution is more likely, the one where a chicken lays an egg out of which comes a new chicken or the one where a chicken gets into an egg and hops inside another chicken?
Dec
11
awarded  Enthusiast
Dec
11
awarded  Enlightened
Dec
11
awarded  Nice Answer
Dec
10
comment Nonlinear optics as gauge theory
Ansatz is fine, one could substitute the word postulate for it, or guess as wikipedia suggests. In his 2D Ising paper, Onsager used "eigenwert" for eigenvalue. Actually, an even better translation would be "proper value". There are a lot of German words that entered science, mainly during the period from the end of the 19th to early 20th century. "Gedankenexperiment" is another one.
Dec
10
comment Nonlinear optics as gauge theory
Look, you are tackling this way too abstractly. Maybe you should start with a specific material with nonlinear optical properties and see how you can describe it. Try to make a gauge-invariant nonlinear field equation for it. If you can't, there's not much point to break your head over it. If you can, you've got a basis to try to generalize. But you'll achieve very little if you can't even model the simplest nonlinear material in this way.
Dec
9
comment Why doesn't air freeze?
I agree that the complete explanation is more complicated. It's true that the exact melting point will depend on the structure that the solid will adopt. But I was more interested in giving a general feeling of why one might expect that small molecules will be more motile over than large ones. Although it is not true in the absolute of course.
Dec
9
answered Why doesn't air freeze?
Dec
8
comment How many Onsager's solutions are there?
I think when I studied the 2D Ising model in the mathphys course I had, we used the Peierl's method. But it's such a long time ago, I barely can remember if we really did the full proof or if it was just mentioned. I'm not sure I still have the text of that course. That's a pity. I'm quite busy lately, and I didn't find the time to read Onsager's paper. Besides I'm a bit upset by Onsager's sloppiness.
Dec
8
comment How many Onsager's solutions are there?
The connection between quaternions and spinors should show that Onsager's original approach probably just nicely maps onto Kaufman's approach. Quaternions form a Clifford algebra, and Spin(n) are also Clifford algebras I think, or at least related. Seems like you can take the +100 points. ;)
Dec
8
awarded  Nice Answer
Dec
6
comment What sort of experiment would directly test time reversal invariance?
If space-time is discrete in ultimate analysis, a violation of Lorentz invariance is not unthinkable. But would this also mean a violation of CPT? Probably depends on the kind of theory.
Dec
4
comment Total number of subatomic particles in the universe. Are they finite ? assuming any of GR or QM or even ST
Thanks, I corrected.
Dec
4
revised Total number of subatomic particles in the universe. Are they finite ? assuming any of GR or QM or even ST
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Dec
4
comment Why won't my door close in the winter?
Just checked the climate of Kazan on the wiki page and it is indeed a humid continental climate. I must say though, it's not clear to me if the OP is saying that the door doesn't close because it is too small to fit or too big to fit?
Dec
4
answered Total number of subatomic particles in the universe. Are they finite ? assuming any of GR or QM or even ST
Dec
4
comment How can I stand on the ground? EM or/and Pauli?
Yes, but it's still only the answer to the question of stability of matter, which is only a subproblem within the larger question that the OP asked. I think sigoldberg1 made a good job of analysing the question at a higher level, but it is clear that explaining each step is a huge task in itself.
Dec
4
revised How can I stand on the ground? EM or/and Pauli?
added 68 characters in body
Dec
4
revised How can I stand on the ground? EM or/and Pauli?
added 588 characters in body; added 196 characters in body