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

Guidance for indexology

  1. Aug 9, 2015 #1
    I recently read that indexology is the art of writing a Lagrangian by just knowing how many dimensions it has and how to contract tensors. I am very interested in this technique, but I cannot find any reference. Can anyone give me a guidance or a reference?
     
  2. jcsd
  3. Aug 10, 2015 #2

    DEvens

    User Avatar
    Education Advisor
    Gold Member

    Um... You read this where? You might get a scalar from this. But a Lagrangian has to satisfy a few more conditions than just being a scalar.
     
  4. Aug 10, 2015 #3
  5. Aug 10, 2015 #4

    DEvens

    User Avatar
    Education Advisor
    Gold Member

    Actually, the first one does help. It talks about the other conditions a Lagrangian must satisfy for an electromagnetic field. That is, you need more than just the dimension and how to contract tensors.
     
  6. Aug 10, 2015 #5
    Oh, I think I didn't express myself clearly.

    The first book is where I first read about indexology and that's why I asked such a question.

    I basically understand the technique. What I want to know is more details. For example, I don't know why only ##\delta_{\alpha\beta}## and ##\epsilon_{\mu\nu\lambda}## is the only two isotropic tensors and I don't even know what are isotropic tensors. That's why I am here asking for reference.
     
  7. Aug 10, 2015 #6

    DEvens

    User Avatar
    Education Advisor
    Gold Member

    Google is your friend.

    http://mathworld.wolfram.com/IsotropicTensor.html
    http://www.damtp.cam.ac.uk/user/reh10/lectures/nst-mmii-chapter3.pdf
    http://www2.ph.ed.ac.uk/~rhorsley/SI12-13_socm/lec08.pdf
    https://www.physicsforums.com/threads/isotropic-tensors.106292/
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook