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  1. P

    QED; electrons and photons, different fields, modes of a common field?

    You meant to say yes. Within the Standard Model, as you say, the photon and electron fields have different properties, therefore have to be treated as separate.
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    Feynman Diagram for Electron-Proton Attraction

    In this case, just don't forget to draw the arrows! However, this seems to me like a careless introduction of Feynman diagrams within a pedagogical text.
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    Feynman Diagram for Electron-Proton Attraction

    This makes no sense, could you please clarify?
  4. P

    Feynman Diagram for Electron-Proton Attraction

    The diagram you show may be useful (but maybe even more so misleading) for a heuristic approach to the scattering problem. Apart from the remark that you would have to include arrows on the lines, one has to notice two important facts: 1.) In quantum field theory, scattering amplitudes are...
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    2D Systems and 4D Minkowski Space: Exploring Path Integrals

    Could you please give a reference regarding the publications you are talking about?
  6. P

    Photonic Properties Determining Charge

    But doesn't your argument break down in temporal gauge, where you set A0=0?
  7. P

    QCD from string theory

    Yes, it is. It allows one to calculate meson, baryon and glueball spectra, form factors, and even incorporates chiral symmetry restoration at high temperature. If you're interested, take a look at some of those papers:
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    QCD from string theory

    Just a remark; the Sakai-Sugimoto model is non-supersymmetric.
  9. P

    Axial anomaly and broken Lorentz invariance

    Yes, I did, thank you! :) Corrected it!
  10. P

    Axial anomaly and broken Lorentz invariance

    The axial anomaly of nonabelian gauge theories actually comes from a broken U(1) symmetry. In QCD, you have U(N_f)_L\times U(N_f)_R chiral symmetry, with both a conserved left-handed current L^\mu and a right-handed one, R^\mu. It is now possible to make a linear combination of those two...
  11. P

    Group velocity at Brillouin zone boundary

    There is a very nice website explaining your example generally (it has different masses instead of different force constants, but you can just rename the constant in the first equation on the webpage). The animation in the bottom...
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    What does the relation for temperature dE/dS=T mean physically?

    The only reason I can think of is: By defining S=k_b \log \Omega, it just works out; for an ideal gas as well as for other systems (that I can't come up with right now). \frac{dS}{dE}=\frac {1}{T(E,...)}\, states that temperature is a measure of the increase in entropy when some energy is...
  13. P

    Holographic Principle: Quantum Gravity & String Theory

    In it's strict mathematical formulation, it is restricted to string theory. I'm not sure about Susskind and t'Hooft, but Maldacena is the one who conjectured it. The black hole entropy was derived without explicit use of string theory, and as such it can be seen as a manifestation of the...
  14. P

    Holographic Principle: Quantum Gravity & String Theory

    The holographic principle manifests itself in string theory in the form of the so-called "AdS/CFT-Correspondence". It was formulated in the late 90's by Juan Maldacena (hence it is also often called "Maldacena Conjecture") and it states a duality between a type IIB string theory on an...
  15. P

    Ax 4 in page 19 of Ticciati's QFT textbook.

    The statement is about a timelike distance four-vector in Minkowski space. Its squared length is negative in the case of a -+++ metric.
  16. P

    Anyone Into Symphonic Metal/Opera Metal?

    You should check out my band Siren's Cry, might be of interest to you:
  17. P

    Wave function is always in abstract space?

    Where did you hear that? Electrons can be observed just as well as photons.
  18. P

    Neglecting terms in a Lagrangian

    In physics, quantities which are small compared to others are simply set to zero as an approximation. This is exactly what happens here.
  19. P

    Energy is borrowed from the vacuum /Virtual Particles

    "Energy is borrowed from the vacuum"/Virtual Particles I know that there are countless threads on virtual particles (some of which I have participated in), but I don't think that this issue has been adressed yet. One common handwaving argument for the existence of virtual particles is the...
  20. P

    Can someone tell me why this doesn't make sense?

    Do you refer to the holographic principle in the form of the AdS/CFT correspondence? If yes, then you should be more careful. It is a conjectured mathematical equivalence that allows one to map thermal states of quantum fields in a lower dimensional space to thermal black holes in a lower...
  21. P

    Higgs bosom is this where energy becomes mass?

    The Higgs boson is the same thing as the higgs field. Your question makes no sense at all.
  22. P

    QED in Coulomb Gauge: Deriving the Coulomb Force and Questions

    Am I missing something important, or isn't the only difference between the addition of your field a(x) and a simple gauge transformation that you call it a "background field" instead of a "gauge transformation"?
  23. P

    Interaction hamiltonian?

    Hermitean conjugate.
  24. P

    What is the difference between an electron and electromagnetic waves?

    Wrong. Energy is an attribute, they carry a certain amount of it, but you can't say that they are energy. Electrons carry charge and are therefore sources of an electromagnetic field. An electromagnetic wave on the other hand can be thought of as a propagating change of such an...
  25. P

    What is with Jazz music?

    What you say may be true to some extent, but there are certainly many people (including me) who enjoy the music just for what it is: music. I don't care about the culture attached to it, I just enjoy it on a musical level. You make it sound as if people only listen(ed) to it because it is/was...
  26. P

    What prevent reaction changing leptons to hadrons?

    True, you can find the experimental data at: .
  27. P

    What prevent reaction changing leptons to hadrons?

    Where did you read that it wasn't possible?
  28. P

    Mathematica Mathematica: ParallelMap getting slower

    Hi, I use ParallelMap with Mathematica on Linux to solve 100 eigenvalue problems on 4 kernels. This operation ist repeated very often, and over the course of time the performance drops significantly. Using top, you can see that the CPU used by the master kernel increases, and the CPU used by...
  29. P

    Background required for general relativity

    I always thought that GR was background-independent...
  30. P

    Why can't we see anything fall into the black hole?

    I'll try with a simple explanation: in flat space (far away from the black hole) we have light cones with an angle of 45° from the horizontal space axis. Now as you get closer and closer to the black hole, the curvature of spacetime makes the light cones bend inwards, which basically means that...
  31. P

    So if spin isn't really spin

    First of all, the physicist's name was Heisenberg, not Heisenburg. Now I see where your confusion comes from: It's semantics. "Complementary parameters" is just a wrong wording: they are actually hermitian operators that obey the uncertainty principle for certain reasons. If you don't know...
  32. P

    So if spin isn't really spin

    Ah, I see. If it is a decent course, they should teach you more about spin eventually! Sorry, it was definitely not meant that way! I just wondered what kind of education you had, because it would've been odd if you were for example a physics major who never heard about the mathematical...
  33. P

    So if spin isn't really spin

    I hate to disappoint you, but there is already something called "moose model" in particle physics! ;)
  34. P

    So if spin isn't really spin

    I don't know your level of education, but I guess one usually learns this in introductory quantum mechanics courses.
  35. P

    So if spin isn't really spin

    Where did you learn that? That's definitely not the meaning of the Heisenberg uncertainty principle.
  36. P

    So if spin isn't really spin

    It is called spin because the generators of the group of spin transformations obey the same algebra as those for angular momentum (SU(2)). So, the analogy to something spinning around is purely mathematical.
  37. P

    Something is broken about black hole theory

    True, didn't notice that at first, sorry. However, my argument still holds.
  38. P

    Something is broken about black hole theory

    Why does the term on the right hand side survive the r->infinity limit? Sure, it goes to zero slower than the others, but if we assume the ideal point r=infinity, it is also zero. You can basically think about it like this: Schwarzschild geometry is asymptotically flat (i.e. minkowski at...
  39. P

    Something is broken about black hole theory

    Why would that be the case? That's not true.
  40. P

    High energy virtual particles

    I think I got you wrong, do you mean the quantization of the vector potential A_{\mu}? Anyways. What you describe here is one distinct Feynman diagram. It is no picture of physical reality...
  41. P

    High energy virtual particles

    This is why one should stick to facts, not to intuition.
  42. P

    High energy virtual particles

    By stating this, you are stating that QED is "wrong". You keep claiming this, but you have nowhere shown something to back you up. What you say is simply not true.
  43. P

    High energy virtual particles

    I agree. When you break down something complex so that the general public can understand it, there is always the danger of losing or mixing up important information, so that the outcome is something completely different than what you originally wanted to convey. One has to be careful!
  44. P

    High energy virtual particles

    Well, this basically goes down to the question whether something like an absolute reality exists, or not. All we can rely on is experimental data, and theories can only be judged by whether they fit the data or not. "Shut up and calculate" might seem like a narrow-minded approach, but it makes...
  45. P

    High energy virtual particles

    I understand that point, but I also think that people should be more understanding when people who have actually studied QFT and know details about the story tell them that they a wrong in certain aspects. It's like people are stuck with a false concept despite all the evidence against it. I...
  46. P

    High energy virtual particles

    I never said that they did. My point is that a physical theory can only answer "why"-questions to a certain degree. At some point, you have to assume fundamental entities within such a theory. In our case the fundamental aspect would be the influence of fields on charges. One could always ask...
  47. P

    High energy virtual particles

    Sorry, maybe I was misinterpreting you! I thought that you interpreted the text in such a way that virtual particles actually were physical objects, sorry! Then why are so many people here claiming that virtual particles are the answer?