Activity for Technically Natural
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Answer | — |
A: What do eigenfunctions and eigenvalues mean physically? $x(t)=a\cdot \sin(t\sqrt{k/m})$ is the only solution that satisfies $x(0)=0$. If you then impose $x(c)=0$, you only get solutions for certain values of $k$. These values are the eigenvalues of the differential operator $-m d^2/d^2 t$ acting on the vector space of functions satisfying the boundary con... (more) |
— | 11 months ago |
| Question | — |
Why is it forbidden for two photons to turn into one? In the context of quantum field theory, why is it impossible for two photons (or other massless bosons like gluons) to collide and produce a single photon? This kind of a process is supposed to be forbidden by momentum conservation, but it was not immediately obvious to me why this is. (more) |
— | 11 months ago |
| Question | — |
Interaction terms in Srednicki's proof of spin-statistics theorem In Srednicki's proof of the spin-statistics theorem for scalar fields ("Quantum Field Theory", section 4), he considers interaction terms, added to the free Hamiltonian, that are Hermitian functions of $$\varphi^+(x)=\int\frac{d^3k}{(2\pi)^32\omega}e^{ikx}a(\mathbf{k})$$ and $$\varphi^-(x)=\int\fr... (more) |
— | about 3 years ago |
| Question | — |
What should our policy be toward rudeness? What should our policy be toward rudeness? I don't think being blunt is a problem, but I do think that calling into question the OP's intelligence is a problem. For example, I don't think there's anything wrong with responding, "Your question is based on a false assumption." However, I think respo... (more) |
— | about 3 years ago |
| Question | — |
How do constraints work in Lagrangian systems? I have a question about the discussion of constrained Lagrangian systems in the book Mathematical Aspects of Classical and Celestial Mechanics by Arnold et al. (section 1.2.5). The Lagrangian system is defined on a manifold $M$. The constraints pick out a submanifold $S$ of the phase space $TM$, a... (more) |
— | over 3 years ago |
| Answer | — |
A: New Category ideas The Papers Category I don't think the "Papers" category would work well for physics. It would get a lot of spam, and I think it would be much more limited in usefulness than the one on Electrical Engineering. The Problems Category The "Problems" category might potentially be useful because... (more) |
— | over 3 years ago |
| Question | — |
How does probability conservation work in Dirac's original formulation of relativistic QM? I asked this question on Stack Exchange, and didn't get an answer, but maybe someone here will be able to help. In non-relativistic quantum mechanics, the normalization condition for position eigenstates is $$\langle y|x\rangle = \delta(y−x).$$ However, this condition is not Lorentz-invariant.... (more) |
— | over 3 years ago |