Beyond ΛCDM with low and high redshift data: implications for dark energy

• Published in: General relativity and gravitation Vol. 52; no. 2
• Main Authors: Dutta, Koushik, Roy, Anirban, Ruchika, Sen, Anjan A., Sheikh-Jabbari, M. M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2020; Springer Nature B.V
• Subjects: Astronomy; Astrophysics and Cosmology; Classical and Quantum Gravitation; Cosmological constant; Dark energy; Differential Geometry; Flux density; Gravity; Mathematical and Computational Physics; Physics; Physics and Astronomy; Quantum Physics; Red shift; Relativity Theory; Research Article; Theoretical; Universe; CMB; Low redshift data; tension; Dark energy
• ISSN: 0001-7701; 1572-9532
• DOI: 10.1007/s10714-020-2665-4

Assuming that the Universe at higher redshifts ( z ∼ 4 and beyond) is consistent with Λ CDM model as constrained by the Planck measurements, we reanalyze the low redshift cosmological data to reconstruct the Hubble parameter as a function of redshift. This enables us to address the H 0 and other tensions between low z observations and high z Planck measurement from CMB. From the reconstructed H ( z ), we compute the energy density for the “dark energy” sector of the Universe as a function of redshift without assuming a specific model for dark energy. We find that the dark energy density has a minimum for certain redshift range and that the value of dark energy at this minimum ρ DE min is negative. This behavior can most simply be described by a negative cosmological constant plus an evolving dark energy component. We discuss possible theoretical and observational implications of such a scenario.