Kavli Affiliate: Chihway Chang
| First 5 Authors: Xianzhe TZ Tang, Dillon Brout, Tanvi Karwal, Chihway Chang, Vivian Miranda
| Summary:
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 $Omega_m$ and Hubble constant $
H_0 $ in a $Lambda$CDM model when data are analyzed individually, and 2) hints
of dynamical dark energy in a $w_0w_a$CDM 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 $Omega_m$ and $ H_0 $ for each
probe when analyzed individually in a $Lambda$CDM framework. We generate mock
datasets in $w_0w_a$CDM cosmologies, fit the individual probes under the
$Lambda$CDM model, and find that expected biases in $Omega_m$ are $sim
0.03$. Notably, the $Omega_m$ differences between probes are consistent with
the values observed in the real datasets. We also observe that mock DESI BAO
datasets generated in the $ w_0w_a $CDM cosmologies will lead to a biased
measurement of $ H_0 $ higher by ($sim1.2$km/s/Mpc) when fitted under
$Lambda$CDM, appearing to mildly improve the Hubble tension, but as the true
underlying $H_0$ is lower, the tension is in fact worsened. We find that the
$Omega_m$ discrepancies, the high BAO $ 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.
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