Abstract
Baryon acoustic oscillations (BAO) provide a robust standard ruler, and can
be used to constrain the expansion history of the Universe at low redshift.
Standard BAO analyses return a model-independent measurement of the expansion
rate and the angular diameter distance as function of redshift, normalized by
the sound horizon at radiation drag. However, this methodology relies on
anisotropic distance distortions of a fixed, pre-computed template (obtained in
a given fiducial cosmology) in order to fit the observations. Therefore, it may
be possible that extensions to the consensus $Łambda$CDM add contributions to
the BAO feature that cannot be captured by the template fitting. We perform
mock BAO fits to power spectra computed assuming cosmological models which
modify the growth of perturbations prior to recombination in order to test the
robustness of the standard BAO analysis. We find no significant bias in the BAO
analysis for the models under study ($Łambda$CDM with a free effective number
of relativistic species, early dark energy, and a model with interactions
between neutrinos and a fraction of the dark matter), even for cases which do
not provide a good fit to Planck measurements of the CMB power spectra. This
result supports the use of the standard BAO analysis and its measurements to
perform cosmological parameter inference and to constrain exotic models. In
addition, we provide a methodology to reproduce our study for different models
and surveys, as well as discuss different options to handle eventual biases in
the BAO measurements.
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