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Paper IPM / Physic / 15341  


Abstract:  
Assuming that the Universe at higher redshifts (z ∼ 4 and beyond) is consistent with model as constrained by Planck satellite data, we reanalyze the low redshift cosmological data to reconstruct the Hubble parameter as a function of redshift in a model independent way. This enables us to address the H_{0} and other tensions between low z observations and high z Planck measurement from CMB. From H(z), we reconstruct the energy density and pressure for the "dark energy" sector of the Universe as a function of redshift and find that the dark energy density has a minimum for certain redshift range and that this ρ_{DE}^{min} is negative. This behavior is most simply described by a negative cosmological constant plus a dark energy sector which has a phantom crossing. We discuss possible theoretical and observational implications of such a scenario.
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