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I Liouville, the second law and chaos

  1. Jan 7, 2017 #1

    haushofer

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  2. jcsd
  3. Jan 7, 2017 #2
  4. Jan 7, 2017 #3

    Demystifier

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  5. Jan 7, 2017 #4

    haushofer

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    Great notes. But somehow I don't yet grasp the idea of the entropy of the second law being a subjective notion. Is this comparable with renormalization, where physical parameters depend on the energy scale one is looking at?and is Invoking chaos necessary in this coarse-graning picture of Liouville's theorem vs the 2nd law?
     
  6. Jan 7, 2017 #5

    Demystifier

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    This is explained even in popular science books, such as
    https://www.amazon.com/Entropy-Demystified-Second-Reduced-Common/dp/9812832254

    In short, entropy counts the number of microscopic realizations of a given macroscopic state. But the notion of the "macroscopic" state is very subjective.

    Yes, that's a good analogy.

    It's usually associated with chaos, but not always. In principle, it is possible to have a second law due to coarse graining without chaos.
     
    Last edited by a moderator: May 8, 2017
  7. Jan 7, 2017 #6

    haushofer

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    Thanks. Your book recommendation seems curious. I've "The physics of information" by Bais and Farmer in my closet and will read up with this coarse graining.
     
  8. Jan 9, 2017 #7

    Demystifier

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    My google search does no find such a book. Are you sure about the title and authors?
     
  9. Jan 9, 2017 #8

    haushofer

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  10. Jan 10, 2017 #9

    Demystifier

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    Ah, it's a paper. :woot:
    You said that it is in your closet, so I assumed that it is a book. Whenever possible, I like to keep papers as pdf's, not as papers in a literal sense. :biggrin:

    Anyway, the paper seems great!

    EDIT: Now I have realized that the paper is published as a chapter in the book "Philosophy of Information", which is a book that I already have.
     
    Last edited: Jan 10, 2017
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