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Question about terminology: ch = cosh?

  1. Oct 20, 2013 #1


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    Gold Member

    I am reading the draft of a paper written by someone whose native language was not English and so who might not have been using the same abbreviations that I am familiar with, or maybe he was using standard ones and I am simply not familiar with the abbreviations involved. I can't ask him, as he is deceased. I quote:
    "The properties of the event plane are described by the homogeneous two-dimensional Lorentz group L:
    x' = xchθ + τshθ
    τ' = xshθ + τchθ
    where the hyperbolic angle θ is the transformation parameter. The relation of θ to the relativity velocity β is given by β = thθ. The coordinate τ = ct,..."

    What are ch, sh, and th? Did he mean cosh, sinh, and tanh? Are his abbreviations standard?
  2. jcsd
  3. Oct 20, 2013 #2


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    Staff: Mentor

    I think so.

    Not in English at least, as far as I know.
  4. Oct 20, 2013 #3


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    Science Advisor

    Yes. I often write ch in place of cosh. Especially when I'm in a rh.
  5. Oct 20, 2013 #4


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    Staff: Mentor

    Yeah, it can be uncomfortable writing stuff when you have a rash. :biggrin:

    I admit I don't read much stuff that uses hyperbolic functions.
  6. Oct 20, 2013 #5
    He is talking about the Lorentz transformation in terms of rapidity rather velocity.
    See http://en.wikipedia.org/wiki/Lorentz_transformation#Rapidity and http://en.wikipedia.org/wiki/Rapidity
    It is clear from those links that he does mean cosh, sinh, and tanh.
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