Testing gravity theory on the cosmological scales using the next generation dark energy surveys

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We studied the problem of whether the modified gravity models, which are proposed to explain the cosmic accelerated expansion, can be really viable solutions or not. To this end, we studied the aspects from the view points of the cosmological consistency, and obtained the following results. (1) We established the method of testing the gravity theory on the cosmological scales using the multipole power spectrum in the galaxy distribution, and demonstrated the usefulness of the method with the SDSS galaxy samples. (2) We clarified the characteristic behaviors and properties of the cosmological models of an f(R) model, the galileon models and its extended versions. We obtained the useful constraints on each model. (3) We found the possibility that a characteristic feature of modified gravity models may appear in the outskirt region of galaxy clusters, and developed a new method for testing gravity by combining X-ray, lensing, and Sunyaev-Zeldovich effect observations of a cluster.