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Homework Help: General relativity - Covariant Derivative Of F(R)

  1. Oct 18, 2012 #1
    In f(R) gravity as http://en.wikipedia.org/wiki/F(R)_gravity ,

    i have problem with the term [ g_ab □ - ∇_a ∇_b ] F(R) , well

    actually is [ ∇_b ∇_a - ∇_a ∇_b ] F(R) , but F is a function of Ricci Factor and Ricci Factor is expressed as a(t) ( scale factor ) . for the a = b = 0 i say this term becomes zero . is it true ?
  2. jcsd
  3. Oct 18, 2012 #2


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    Can you re-write your post so that it makes (more) sense ?
  4. Oct 19, 2012 #3
    I don't know anything about f(R) gravity theories, but that expression is clearly zero if the torsion tensor vanishes.
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