Kavli Affiliate: Wayne Hu
| First 5 Authors: Tanisha Jhaveri, Tanvi Karwal, Wayne Hu, ,
| Summary:
Under $Lambda$CDM, recent baryon acoustic oscillation (BAO) distance
measures from DESI, which favor a low matter density $Omega_m$, are in
moderate $2-3sigma$ tension with cosmic microwave background (CMB)
observations. This tension appears alternately as a preference for the sum of
neutrino masses dropping below the $sum m_nu = 0.06$eV value required by
neutrino oscillation measurements to formally negative values; a discrepant
value of $Omega_m$ at 0.06eV; or preference for dynamical dark energy beyond
$Lambda$CDM. We show that this tension largely arises from the CMB lensing
constraints on the calibration of the sound horizon for geometric measurements
and relies on the measurement of the reionization optical depth $tau$ from
large-angle CMB polarization to set the lensing amplitude. Dropping these
constraints removes the neutrino tension at $sum m_nu=0.06$eV entirely,
favoring $tau = 0.091pm 0.011$ in $Lambda$CDM. Beyond $Lambda$CDM, it
brings the preference for $w_0-w_a$ dynamical dark energy to below $95%$ CL.
We explore the freedom in interpreting the low-$ell$ EE polarization
constraint due to analysis choices and reionization modeling beyond the
standard step-function assumption and find that this drops the neutrino tension
in $Lambda$CDM to below $95%$ CL. Alternately, this raising of $tau$ can
also be achieved by the same reduction in large-scale curvature fluctuations
that also ameliorates the low-$ell$ temperature anomaly.
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