Tsujikawa, Phys. Rev. D 77, 023507 (2008)
Tsujikawa, Phys. Rev. D 77, 023507 (2008)
Tsujikawa, Phys. Rev. D 77, 023507 (2008)
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A. Non-local gravity< Action >g =det(g ö÷ )f : Some function: Metric tensorNo. 27Λ : Cosmological constantNon-local gravityBy introducing two scalar fields and , we find・By the variation of the action in thefirst expression over ø , we obtain(or )Substituting this equation into the action in thefirst expression, one re-obtains the starting action.: Covariant derivative operator: Covariant d'Alembertian: Matter LagrangianQ: Matter fields