Kavli Affiliate: George Efstathiou
| First 5 Authors: George Efstathiou, , , ,
| Summary:
This paper presents an alternative way of analysing Baryon Acoustic
Oscillation (BAO) distance measurements via rotations to define new quantities
Dperp and Dpar. These quantities allow simple tests of consistency with the
Planck LCDM cosmology. The parameter Dperp is determined with negligible
uncertainty from Planck under the assumption of LCDM. Comparing with
measurements from the Dark Energy Spectroscopic Instrument (DESI), we find that
the measurements of Dperp from Data Release 2 (DR2) move into significantly
better agreement with the Planck LCDM cosmology compared to DESI Data Release 1
(DR1). The quantity in the orthogonal direction Dpar provides a measure of the
physical matter density omega_m in the LCDM cosmology. The DR2 measurements of
Dpar remain consistent with Planck LCDM despite the substantial improvement in
their accuracy compared to the earlier DR1 results. From the comparison of
Planck and DESI BAO measurements, we find no significant evidence in support of
evolving dark energy. We also investigate a rotation in the theory space of the
w_0 and w_a parameterization of the dark energy equation-of-state w(z). We show
that the combination of DESI BAO measurements and the CMB constrain w(z=0.5) =
-0.996 pm 0.046, i.e. very close to the value expected for a cosmological
constant. We present a critique of the statistical methodology employed by the
DESI collaboration and argue that it gives a misleading impression of the
evidence in favour of evolving dark energy. An Appendix shows that the
cosmological parameters determined from the Dark Energy Survey 5 Year supernova
sample are in tension with those from
DESI DR2 and parameters determined by Planck.
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