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As time goes on, I grow more disillusioned with quantum field theory.


Aug
24
awarded  Revival
Aug
15
comment What are Maximally Helicity Violating (MHV) Amplitudes?
Neat. What is it that makes all amplitudes with all helicities the same sign (or with just one opposite sign) vanish?
Jul
28
comment How is intensity defined for quantized EM fields?
I think the Intensity becomes an operator which has a form very similar to the electromagnetic Hamiltonian (i.e. with $|E^2|$)
Jul
10
awarded  Yearling
May
13
awarded  Popular Question
Mar
26
awarded  Popular Question
Mar
13
comment Do the norms of the total and the orbital angular momentums commute? If yes, why is there a problem with 2p_{1/2}?
Of course they do commute. The problem is that $\vec{L}^2$ and $\vec{S}^2$ may not commute with the Hamiltonian $H$. If the fine structure splitting of the hydrogen atom is treated exactly by the methods of relativistic quantum theory, the solutions are superpositions of states of orbital angular momenta ($\ell = 0, 2, 4, ...$ or $\ell = 1, 3, 5, ...$), because the relativistic Hamiltonian does not commute with $\vec{L}^2$.
Feb
16
comment Do Standard Model Yukawa couplings depend on the gauge choice?
@Shep Yes, you can think of it that way. Otherwise you have to do a little more work to identify the conserved charge, and identify that as $Q_\text{new}$.
Feb
15
comment Do Standard Model Yukawa couplings depend on the gauge choice?
@Shep Srednicki assigns the Higgs a hypercharge of $Y=-1/2$ (which is opposite from most everyone else's definition). As a result, Srednicki's Higgs field is rotated by $\pi/2$ around the isospin-$y$ axis, followed by $C$-conjugation with respect to everyone else Higgs's field [analog of the $G$-parity in hadron physics].
Feb
14
answered Do Standard Model Yukawa couplings depend on the gauge choice?
Feb
9
comment Chocolate dynamics
Is this more appropriate for math.SE? (Seems like a pure diff. geom. problem)
Jan
24
asked In what way can a Solar storm hitting the Earth disrupt electronic equipment
Jan
16
comment Do particle decays happen instantly?
The decaying particle's wavefunction fades out, the products' wavefunction fades in. The "pop" occurs due to wavefunction collapse of QM when the detector takes a look.
Jan
5
answered Are there eight or four independt solutions of the Dirac equation?
Jan
5
answered Electron orbitals and the circular membrane vibrations
Jan
5
answered Why do some bound states disappear in a discontinuous way?
Jan
5
comment Can “particle” waves break as ocean waves do?
@Floris has the right answer. Ocean waves break because of nonlinearities. The schödinger eqn is linear, and so cannot lead to 'breaking'.
Jan
1
revised Does the diffracted electron radiate photons?
added 19 characters in body
Dec
31
comment Does the diffracted electron radiate photons?
@annav Bremsstrahlung radiation occurs for the double-slit case, too. Also recall that in these experiments that the detection screen is placed far beyond the position of the double slits, so that even the outer-most parts of the observed interference patten result from small-angle deflection. Also remember that the amplitude for truly large-angle deflections (where significant bremsstrahlung occurs) is much too low to readily observe the interference pattern out there. A high-intensity beam would be needed for observation of pattern at such angles.
Dec
31
answered Does the diffracted electron radiate photons?