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Problem with notation

  1. Oct 30, 2012 #1
    Hi everyone!

    I have a stupid question. It's about the notation used sometimes in the Covariant Derivative.

    For example, if somebody tells me:

    "If you have a Killing Vector Field [itex]\xi[/itex] with timelike orbits, you can define a time coordinate satisfying [itex]\nabla_{\xi}t=1[/itex]"

    what does this last equation means?

    I suppose that it has something to be with the normalisation (using +--- signature) , but how do i get the usual [itex]\xi_{a}\xi^{a}=1[/itex] notation from it?$

    Thanks in advance!
  2. jcsd
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