Recent content by QuantumCosmo

Hi, I once read a physics comic that went something like this: two people, one was floating in the air and told the other "I have refuted my belief in gravity" ... I think he then proceeds to refute several other things and they all vanish/dont work for him anymore... (I think there...

Hi, lets say we have the scattering process e^- + \nu_{\mu} \rightarrow \mu^- + \nu_e via the weak interaction. This would then be mediated by a W-Boson, right? Now my question ist: Which one? The Feynman-Diagramm should then look like the one on the right...

Hi, what do you think are the most important Feynman diagrams (or probably better: what do you think are the most important processes in particle physics)? Thanks, Quantum Cosmo

Hi, I was wondering if the spin of a particle changed under Lorentz boosts. I think what it comes down to is if S^2 commutes with the generators of Lorentz boosts (the components of S only generate the rotations of the spinor I think). I think that should be true (an electron should always be a...

So that would mean the solutions to the hydrogen atom do form a complete set. Its what I thought but somehow not what my professor seems to think... Thanks for the answer :)

Hi, I was wondering if the bound solutions to the radial part of the hydrogen atom form a complete set for the functions in L^2(0,\infty). I know that the laguerre polynomials are complete and that they only differ from the radial solutions by factors of x^l * exp, so I thought that they would...

Hm, I always thought that the idea of eigenvectors to continuous "eigenvalues" made no sense anyway (there are no continuous eigenvalues. the position operator for example has no eigenvalues at all. its spectrum is the real numbers, but it has no eigenvalues). in a mathematical sense, one has to...

Ok, so it is really a practical decision rather than a physical necessity? Thank you! :)

Hm, yeah, it's certainly true that the mathematics is simpler and a lot of things we use - for example the spectral theorem - require operators to be linear. But I can't seem to find a physical reason for why that should be so. The only thing that comes to mind is the requirement of real...

Hi, I was wondering: What is the physical reason for only choosing linear operators to represent observables?

Hi, I am currently learning for a test in theoretical physics and in one of my books it was mentioned that there is a reason why the correspondence principle only works in cartesian coordinates. Sadly, they didn't give that reason nor a book or website where one could look it up if interested...

Yeah... because I don't understand this Kogut Susskind solution to the U(1) problem at all...

Hi, I was wondering about the U(1)_A problem. The Lagrangian exhibits a (in the limit of vanishing quark masses) U(1)_A symmetry but due to the chiral anomaly, the current J_5^{\mu} is not conserved: \partial_{\mu}J_5^{\mu} = G\tilde{G} + 2i\bar{u}\gamma_5 u +... The G\tilde{G} term...

Hi, I have found an article that explains why the \theta_{weak} term can be eliminated. It seems, though, this is different from what we discussed here (although I don't really understood what they were doing...) A. A. Anselm and A. A. Johansen, Nucl. Phys. B407(1993) 652

Hm, yeah, I think I might have understood it :) My whole problem is that my QFT basics aren't that good... and that I often have problems with (I guess) very easy parts, for example those U(1) transformations. I now suspect (after what you just wrote) that q_L\rightarrow e^{i\alpha/3}q_L...