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Modified theories of gravity, e.g. f(R) gravity

  1. May 18, 2014 #1
    Hello Everybody,

    It is quite good experience to spend time on this helpful forum, but I am posting here for the first time, I wish it to be a good experience:)

    Could anybody help me in elaborating the folllowing statements:

    1): modified theories of gravity have more degree of freedom

    2): in f(R) theory of gravity Since the curvature tensors contain second
    derivatives of the metric, the resulting equations of motion will in general be fourth order,
    "gravity is then carried also by massless spin-0 and spin-1 fields in general relativity".

    3): why do they replace the variable of f(R) gravity with some scalar field?

    I want a satisfactory explanation of above statements.
    Thanking in advance!
    Last edited: May 18, 2014
  2. jcsd
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