1. Introductionrn Our understanding of the universe has been greatly advanced over the last two decades and a standard cosmology paradigm is now well established. Standard cosmology is based upon the cosmological principle that our universe is statistically homogeneous and isotropic. It is also based upon general relativity with a non-zero cosmological constant. In such a framework, our universe is composed of about 4% ordinary matter （baryonic matter）,
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