Speaker
Ewan Chamberlain
(University of Sussex)
Description
The cosmic microwave backround (CMB) and baryon acoustic oscillations (BAO) provide precise benchmarks for measuring the expansion history of the universe. In particular, the CMB angular scale measurement $\theta_*$, which determines the ratio of the sound horizon to the angular diameter distance to the last scattering surface, offers a robust constraint on cosmological models independent of late-time physics. We show that the null energy condition of general relativity imposes strict limits on the BAO observables used by DESI. We also identify which regions of parameter space in the CPL parameterization $w(a) = w_0 + w_a(1-a)$ remain viable while satisfying these conditions.
Author
Prof.
Antony Lewis
(University of Sussex)
Co-author
Ewan Chamberlain
(University of Sussex)
