Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A Asymmetry parameter while relating proper time with distance

  1. Aug 16, 2017 #1
    In special relativity, we know, (proper time)^{2} = - (proper distance)^{2}. But, in Causal Dynamical Triangulations (CDT), they introduce an asymmetry parameter \alpha as, (proper time)^{2} = - \alpha (proper distance)^{2}

    [Q. 1] Can you please explain me about, why we need to introduce \alpha ? And, Is there is any useful resources to learn more about the role of \alpha in Quantum Gravity? Or, Any derivation relating to asymmetry parameter with proper time and proper distance?

    [Q. 2] In most of the research in CDT, why they prefer to choose \alpha to be 1? Concrete reason needed!

    [Q. 3] Does CDT prefer Time-reversal symmetry?

    With thanks,

    P.S: This question was primarily asked in Research Gate.
    Last edited by a moderator: Aug 16, 2017
  2. jcsd
  3. Aug 16, 2017 #2


    User Avatar
    Science Advisor

    I hope I'm not disappointing you, but if you mean by "proper distance" the spacetime interval, then this is not true in general. It is only true if the proper time is that of an inertial observer. The Euclidean analog is that the length of a path between two points equals the distance if the path is straight.
  4. Aug 24, 2017 #3


    User Avatar
    Science Advisor

    I hope I'm not disappointing you, but proper time is equal to (minus) proper distance along any time-like curve ##C##, i.e.
    $$\int_C d\tau =-\int_C ds $$
    not only along trajectory of an inertial observer. Indeed, many people tried to explain that to you in another thread, but you still seem not to get it.

    Anyway, it doesn't help to answer the OP's question.
    Last edited: Aug 24, 2017
  5. Aug 25, 2017 #4


    User Avatar
    Science Advisor

    Yes, I wrote that post right before I started my topic on grav.time dilation. Infinitesimally, as you write it down, you're right of course.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted