Imperial College London
Alternate

Prof Joao Magueijo

Faculty of Natural Sciences, Department of Physics

Professor of Physics
 
 
 
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Contact

 

j.magueijo Website

 
 
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Location

 

Huxley BuildingSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Gubitosi:2016:06/002,
author = {Gubitosi, G and Lagos, M and Magueijo, J and Allison, R},
doi = {06/002},
journal = {Journal of Cosmology and Astroparticle Physics},
title = {Bayesian evidence and predictivity of the inflationary paradigm},
url = {http://dx.doi.org/10.1018/1475-7516/2016/06/002},
volume = {2016},
year = {2016}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - In this paper we consider the issue of paradigm evaluation by applying Bayes' theorem along the following nested hierarchy of progressively more complex structures: i) parameter estimation (within a model), ii) model selection and comparison (within a paradigm), iii) paradigm evaluation. In such a hierarchy the Bayesian evidence works both as the posterior's normalization at a given level and as the likelihood function at the next level up. Whilst raising no objections to the standard application of the procedure at the two lowest levels, we argue that it should receive a considerable modification when evaluating paradigms, when testability and fitting data are equally important. By considering toy models we illustrate how models and paradigms that are difficult to falsify are always favoured by the Bayes factor. We argue that the evidence for a paradigm should not only be high for a given dataset, but exceptional with respect to what it would have been, had the data been different. With this motivation we propose a measure which we term predictivity, as well as a prior to be incorporated into the Bayesian framework, penalising unpredictivity as much as not fitting data. We apply this measure to inflation seen as a whole, and to a scenario where a specific inflationary model is hypothetically deemed as the only one viable as a result of information alien to cosmology (e.g. Solar System gravity experiments, or particle physics input). We conclude that cosmic inflation is currently hard to falsify, but that this could change were external/additional information to cosmology to select one of its many models. We also compare this state of affairs to bimetric varying speed of light cosmology.
AU  - Gubitosi,G
AU  - Lagos,M
AU  - Magueijo,J
AU  - Allison,R
DO  - 06/002
PY  - 2016///
SN  - 1475-7516
TI  - Bayesian evidence and predictivity of the inflationary paradigm
T2  - Journal of Cosmology and Astroparticle Physics
UR  - http://dx.doi.org/10.1018/1475-7516/2016/06/002
UR  - http://hdl.handle.net/10044/1/38910
VL  - 2016
ER  -
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