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  1. L

    I Lorenz gauge, derivative of field tensor

    Fμν = ∂μAν- ∂νAμ ∂μFμν = ∂2μAν - ∂ν(∂μAμ) = ∂2μAν Why ∂ν(∂μAμ) and not ∂μ∂νAμ ? And why does ∂ν(∂μAμ) drop out? thank you
  2. L

    I Reading suggestions about the "nature of time"

    Why do I perceive "now" as a special moment compared to all the other moments in my life, past and present? Which physic equation, concept, theory accounts for one of the most human conscious experience, the perception that time flows, that the past becomes the present, that the present becomes...
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    I Reading suggestions about the "nature of time"

    For some strange reason I have not found this site before. Looks perfect! Thanks PAllen!
  4. L

    I Reading suggestions about the "nature of time"

    That looks very good and might be just what I wanted. I will check it out at my library on Monday! Thanks George!
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    I Reading suggestions about the "nature of time"

    Thanks so far for your answers. I am still interested in thoughts about the nature of time from physicists that go beyond the pure operational approach. Again: Does anybody know of papers, talks or chapter of books where trained physicists speculate about what time is (or might be) besides...
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    I Reading suggestions about the "nature of time"

    Repeating? You mean, repeating in time?
  7. L

    I Reading suggestions about the "nature of time"

    This I knew, too. But I wanted to know what a clock is. Can you explain it without time?
  8. L

    I Reading suggestions about the "nature of time"

    What is a clock? Can you define it without the concept of time?
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    I Reading suggestions about the "nature of time"

    There are quite some pop-sci books (by Greene, Smolin, Carroll and others) that deal with the "nature of time". Why does time appear to flow? Why is there a special moment, the "now"? Does simultaneity in SR imply a block universe? Why time-symmetric laws but a time-unsymmetric universe? Does...
  10. L

    I Equation of motion Chern-Simons

    Fantastic! Thanks Samalkhaiat! Kronecker Deltas from derivatives and indices swapping in the Levi-Civita. Got it. I must study a little tensor calculus..
  11. L

    I Equation of motion Chern-Simons

    Orodruin, I really appreciate your time and effort. I read carefully all your posts in this thread and the link you gave. But unfortunately, I still can not answer my initial question. Maybe I try somewhere else. Thank you!
  12. L

    I Equation of motion Chern-Simons

    L = aμ∂νaλ ∂L/∂aμ - ∂ν (∂L/∂(∂νaμ)) = ∂vaμ - ∂v ? I do not know what and how to differentiate in the second term. Also, I need to add two identical terms to get the factor two. But there is a minus sign.
  13. L

    I Equation of motion Chern-Simons

    I differentiate γεμνλaμ∂νaλ w.r.t. aμ and I get γεμνλ∂νaλ and γεμνλaμ∂νaλ w.r.t. ∂νaλ which gives γεμνλaμ. Thus γεμνλ∂νaλ - γεμνλaμ = 0 , which is not 2γεμνλ∂νaμ = 0.
  14. L

    I Equation of motion Chern-Simons

    I get the equation but without the 2 in front. I do not see how the 2 comes about. How to sum over the indices. I find the indices confusing. Hence my question.
  15. L

    I Equation of motion Chern-Simons

    Right. And a derivative in front of one a. Do I get one term from the RHS and one from the LHS of equation of motion and then I add them together?
  16. L

    I Equation of motion Chern-Simons

    The Lagrangian (Maxwell Chern-Simons in Zee QFT Nutshell, p.318) has as equation of motion: Where does the 2 in front come from? Thank you very much
  17. L

    I Particles more fundamental than fields

    In this Nima Arkani-Hamed paper on page 5 I found the sentence: These constraints are an artifact of using fields as auxiliary objects to describe the interactions of the more fundamental particles. In Schwartz's QFT book I also get away with the impression that the Poincaré irreps (i.e...
  18. L

    I Transforming a matrix

    There does not happen to be some software for such kind of calculations? Also, is it easier to transform the triangle matrix back into the original form than the other way around?
  19. L

    I Transforming a matrix

    That sounds good. But that way I will not get the top row given in the transformed matrix. Because the row simply does not appear anywhere in the original matrix, so I can not swap it to the top!
  20. L

    I Transforming a matrix

    Thanks for the replies. But still not quite clear. As I understand multiplying is useless in this case. I can just add rows to get zeroes. To be concrete , what about the tenth line in the transformed matrix (0000 0000 0011 0011 0011 0011), which rows do I have to add to get this transformed...
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    I Transforming a matrix

    I want to transform the first matrix below into the second one. The book ( Neutsch, "Coordinates") says this can be done by elementary transformation. I guess he means by some Gaussian elimination. But the entries of the matrix are from the finite field 2, so I can not multiply rows, that would...
  22. L

    I Fermions Bosons vertices in SM - but no SUSY

    In the Standard Model fermions interact via exchanges of massless (virtual) spin-1 particles. Fermions are turned into a boson. How is that different from the SUSY transformation that turns fermions into bosons?
  23. L

    B Rindler - uniform acceleration

    So a light signal is sent off some space behind me. At the same time I start accelerating extremely quickly. Even though the light signal will always be faster than me it will never catch up with me. I have difficulties to understand that something that is always faster than you can still never...
  24. L

    I Havil's book "Gamma" page 57, formula

    Where does the 1 in the last line come from? Thank you!
  25. L

    Insights Interview with a Theoretical Physicist: Sabine Hossenfelder - Comments

    Nice overall interview. But this must probably the dumbest thing she ever said: I have never heard of the fact that “physical models are commonly regarded as beautiful and in a sense minimal” and even if that was so I don’t know why it would matter. Yes, quite possibly it’s a pretty bad idea to...
  26. L

    I Dimensionless and dimensioned fundamental constants

    Some last words before this thread disappears into oblivion. It is always amazing to see how much physics and deep insight someone can gain from dimensional analysis!
  27. L

    I Dimensionless and dimensioned fundamental constants

    That makes sense. But when we compare Planck mass and Planck time with other mass and time scales. Like described here
  28. L

    I Dimensionless and dimensioned fundamental constants

    Perhaps, one final question. What physical meaningful observation/ conclusion can we make about the Planck units? They are special units after all, ratios of three (dimensional) constants. The fact that the Planck mass is many orders higher than Planck time and length, would be one, as I read...
  29. L

    I Dimensionless and dimensioned fundamental constants

    That's good stuff. What got me confused, among other things, was the Bronstein cube, that also appears in the opening chapter of Zee's "Einstein gravity", which makes you think that by increasing c, h or G gets you deeper in the domain of the respective theories.
  30. L

    I Dimensionless and dimensioned fundamental constants

    I'm convinced now. If I choose Planck units for measuring, it becomes super-obvious that whenever I measure a different c,h,G my Planck units change as well. Thanks everybody!
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