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Jul
12
awarded  Critic
Jul
12
answered Calculate amount of energy based on height of object
Jul
12
comment Applications of physics beyond QFT
I really couldn't say about GR: surely what they are doing at NASA is beyond-textbooks level; unfortunately this one has not seen any experimental realisation yet even though they are designing the first experiments.
Jul
12
comment Applications of physics beyond QFT
Broadly speaking a TFTs (topological field theories) differ from QFTs because while the point of the latter is to calculate expectation values/n-point functions etc ,the former is used to compute topological invariants. For what concerns its experimental realisation you have plenty of experimental results agreeing with the theory, especially in condensed matter systems (Dirac Points in graphene, Anderson localisation, spin liquids, quantum hall...)
Jul
12
revised Existence of negative temperatures and the definition of entropy
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Jul
11
comment Existence of negative temperatures and the definition of entropy
Nanite, why do you say a spin inversion experiment cannot be described by a micro canonical nor canonical ensemble??
Jul
11
comment Existence of negative temperatures and the definition of entropy
amlrg-ok for a classical system, but Equipartition theorem does not always hold for quantum systems (when kT is smaller than $\Delta E$).
Jul
11
comment Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?
I think it won't work because the exponential would depend on $|\psi|^2$ as well.
Jul
11
awarded  Citizen Patrol
Jul
11
awarded  Yearling
Jul
10
answered Apparent weight on a hill and in a ditch
Jul
9
comment Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?
Do you know a nice way to show the conservation of $ E$ different from brute force computation?
Jul
9
revised Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?
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Jul
9
revised Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?
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Jul
9
comment Proof of the conservation of the energy functional for the Gross-Pitaevskii equation?
1) Even if I read that book already I didn't remember that. Thank you. 2) Of course you are right, my mistake; I will amend the question
Jul
9
revised Applications of physics beyond QFT
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Jul
9
answered Applications of physics beyond QFT
Jul
9
awarded  Commentator
Jul
9
comment How to replace $T$-product with retarded commutator in LSZ formula?
I know wikipedia may not give you much confort as a reference but there they introduce the retarded propagator (with the same expression you have above) and there is no assumption on the picture used.
Jul
9
comment How to replace $T$-product with retarded commutator in LSZ formula?
I am actually pretty sure Wick's applies to your problem, and in general regardless of the picture considered!.The whole point of deleting terms in the expansion of the time-ordered product(all non-fully-contracted products)is that any expression of the kind $<0|\phi^\dagger...\phi|0>$ is zero because $\phi$ annihilates the vacuum.So $<0|\phi^\dagger=0=\phi|0>$. And this is true in any picture.