Uniting the Observed Dynamical Dark Energy Preference with the Discrepancies in Ωm\Omega_m and H0H_0 Across Cosmological Probes

Dec 5, 2024
17 pages
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Abstract: (arXiv)
Recent results from Type Ia Supernovae (SNe), baryon acoustic oscillations (BAO), and the cosmic microwave background (CMB) indicate 1) potentially discrepant measurements of the matter density Ωm\Omega_m and Hubble constant H0 H_0 in a Λ\LambdaCDM model when data are analyzed individually, and 2) hints of dynamical dark energy in a w0waw_0w_aCDM model when data are combined in a joint analysis. We examine whether underlying dynamical dark energy cosmologies favored by real data would result in biases in Ωm\Omega_m and H0 H_0 for each probe when analyzed individually in a Λ\LambdaCDM framework. We generate mock datasets in w0waw_0w_aCDM cosmologies, fit the individual probes under the Λ\LambdaCDM model, and find that expected biases in Ωm\Omega_m are 0.03\sim 0.03. Notably, the Ωm\Omega_m differences between probes are consistent with the values observed in the real datasets. We also observe that mock DESI BAO datasets generated in the w0wa w_0w_a CDM cosmologies will lead to a biased measurement of H0 H_0 higher by (1.2\sim1.2km/s/Mpc) when fitted under Λ\LambdaCDM, appearing to mildly improve the Hubble tension, but as the true underlying H0H_0 is lower, the tension is in fact worsened. We find that the Ωm\Omega_m discrepancies, the high BAO H0 H_0 relative to CMB, and the joint dynamical dark energy signal itself are all related effects that could be explained simultaneously with either new physics or new systematics. While we find it is possible to unite many of the discrepancies seen in recent analyses along a single axis, our results underscore the importance of understanding systematic differences in datasets, as they have unique impacts in different cosmological parameter spaces.
Note:
  • 17 pages, 8 figures, 2 tables