Recent content by liorde

  1. L

    What is the Precise Heuristic Argument that Leads to Noether's Theorem

    I excluded time because I used a 2D space analogy, which was easy to illustrate in a figure. I'm interested in the idea, so it doesn't matter if I use time or not.
  2. L

    What is the Precise Heuristic Argument that Leads to Noether's Theorem

    Hi, I'm confused about the exact interpretation of Noether's theorem for fields. I find that the statement of the theorem and its proof are not presented in a precise manner in books. My main question is: what is the precise heuristic argument that leads to Noether's theorem? The question...
  3. L

    Are Poisson Brackets Consistent in Electromagnetic Field Theories?

    So what is the formulation? Or where can I find it? When I tried to write down the Poisson bracket formulation myself, I ran into problems. Here is my attempt: The coordinates are {A^\mu }({\bf{x}}) where \mu runs over the space-time indices and {\bf{x}} runs over all space points. The...
  4. L

    Physics Not Presented Rigorously Enough

    I am a physics student, doing my graduate degree. I am wondering if anyone else feels like me concerning the following topic: Physics is usually presented in a very imprecise way, and it would be much easier to understand if it would be presented more precisely. I felt this way towards all...
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    Are Poisson Brackets Consistent in Electromagnetic Field Theories?

    Since I couldn't find any reference on the subject of Poisson bracket formalism of classical field theory, I'm posting a few question here: A) What are the Poisson brackets of the source-less EM field? B) Does the law that the Poisson brackets between a dynamical variable and its conjugate...
  6. L

    Why can't any missile carry a nuclear warhead?

    Hi, Question about nuclear weapons: Often you hear about a missile that is capable of carrying a nuclear warhead. But actually, why can't any missile be capable of this? Just take your favorite missile, build for it a nuclear warhead which is the same shape and size as the missile's...
  7. L

    Lorentz Generators: (J and M) vs. S

    I'm sorry, but at the time (and for a long while) I didn't have any means of connecting to the internet, for technical reasons... And now I wanted to ask some more questions about this subject, but to approach it from a different angle, and that is why I opened a new thread (I also posted it in...
  8. L

    Lorentz Generators: (J and M) vs. S

    Maybe the word "internal" should have been used... I'm not sure what I mean, but I hear people referring to spin as generating an "internal" transformation. In non relativistic quantum mechanics (of particles), when we want to discuss spin we add to the wave function a parameter s, which...
  9. L

    Lorentz Generators: (J and M) vs. S

    (if I am not even wrong, please let me know :smile:) The generators of the (proper-orthochronous) Lorentz transformations are usually denoted by {J_{\mu \nu }} or by {M_{\mu \nu }}. They consist of angular momentum generators and boost generators. When discussing spinors, the notation changes...
  10. L

    The meaning of the addition of the spin generator to the Lorentz generators

    Hi, Thanks again for the answers! Your last paragraph raises some of my original questions again: Thanks
  11. L

    The meaning of the addition of the spin generator to the Lorentz generators

    Thanks for your help! I'm still a little bit confused... So you're saying that the commutation relations of the algebra (= the structure constants) do not include all the information about the group? Two algebras (e.g L and L+S) can have the exact same commutation relations but correspond to...
  12. L

    The meaning of the addition of the spin generator to the Lorentz generators

    You say that But \left\{ {{L_{\mu \nu }}} \right\}, defined in (1.2.24), is an "arbitrary" set of operators that satisfy the commutation relations, so it by itself should give rise to all the different representations (corresponding to the different eigenvalues of {J^2}) with no need to add...
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    The meaning of the addition of the spin generator to the Lorentz generators

    Ramond, Field Theory: A Modern Primer, Second Edition, Chapter 1, page 7. Here is the link: http://books.google.co.il/books?id=Ctr9K61fY4kC&lpg=PP1&pg=PA7#v=onepage&q&f=false Look at the last paragraph. I've seen at least two more references using this method (although I might have exaggerated...
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    The meaning of the addition of the spin generator to the Lorentz generators

    When constructing the Lie algebra of the Lorentz Transformation, the references usually start with an infinitesimal proper-orthochronous transformation, and then find the infinitesimal generators. Let's call the set of these generators L. after finding L, the references usually compute the...
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