1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Notation question - what does ! mean?

  1. Oct 8, 2009 #1
    Notation question - what does "!" mean?

    1. The problem statement, all variables and given/known data
    Hi, this is part of a question, in the context of rotation of the Lagrangian:

    x_i -> [tex]O[/tex]_ij.x_j, summation over j !

    My question is: what does the " !" after the j mean?


    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 8, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Pyroadept! :smile:

    (try using the X2 tag just above the Reply box :wink:)

    xi -> Oijxj is written in the "Einstein summation convention", where any repeated index is summed over.

    I don't think the ! means anything, except happiness ! :smile:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook