Abstract
The ‘standard’ model of cosmology is founded on the basis that the expansion rate of the universe is accelerating at present — as was inferred originally from the Hubble diagram of Type Ia supernovae. There exists now a much bigger database of supernovae so we can perform rigorous statistical tests to check whether these ‘standardisable candles’ indeed indicate cosmic acceleration. Taking account of the empirical procedure by which corrections are made to their absolute magnitudes to allow for the varying shape of the light curve and extinction by dust, we find, rather surprisingly, that the data are still quite consistent with a constant rate of expansion.
Highlights
There are several approaches to making SN Ia ‘standardiseable candles’
But this cannot be used to compare models, since it is tuned to be 1 per degree of freedom for the ΛCDM model by adjusting an arbitrary error σint added to each data point
This has been criticised[12,13], the method continues to be widely used and the results presented without emphasising that it is intended only for parameter estimation for the assumed (ΛCDM) model, rather than determining if this is the best model
Summary
The ‘standard’ model of cosmology is founded on the basis that the expansion rate of the universe is accelerating at present — as was inferred originally from the Hubble diagram of Type Ia supernovae. Empirical corrections are made to reduce the scatter in the observed magnitudes by exploiting the observed (anti) correlation between the peak luminosity and the light curve width and the colour[4,5]. Other such correlations have since been found e.g. with the host galaxy mass[6] and metallicity[7]. In this work we present an improved maximum likelihood analysis, finding rather different results
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