Periodic Reporting for period 3 - BePreSysE (Beyond Precision Cosmology: dealing with Systematic Errors)
Período documentado: 2020-06-01 hasta 2021-11-30
The avalanche of data of the past 20 years has propelled cosmology into the precision era: a
standard cosmological model has been established, precision tests have been performed, cosmological
parameters of the model are measured with ~1% precision. Sophisticated statistical techniques have been developed to analyse these data sets and reach these
remarkable achievements. The next challenge cosmology has to meet is to enter the era of accuracy. The
precision of a measurement, indicated by the number of significant figures, accounts for statistical errors.
Accuracy quantifies the closeness of the measurement of a quantity to that quantity's true value, which is
the realm of systematic errors. Accuracy is the new precision.Forthcoming observational effort promise to achieve major
advances in answering a number of big questions, with deep links to fundamental physics: unveil the nature
of dark energy, shed light on dark matter, measure the neutrino mass, understand the mechanism driving
cosmological inflation etc. The path towards answering these questions is a challenging one. The analysis
and interpretation of the data (if not also the survey planning) will need to be revisited in light of the
unprecedented precision enabled by the new data. How can accuracy keep up with increased precision?
Precision without accuracy is dangerous, as highly significant (but wrong) results may be inferred. How can
we make sure that the systematic error budget is known and safely below the statistical error?
Without an effective treatment of
systematic errors (from mitigation to full accounting) the power of the next generation cosmological surveys
will be seriously compromised. I propose to face this challenge by developing a comprehensive
treatment of systematic errors with the goal to minimize, uncover, quantify and account for
otherwise unknown differences between the interpretation of a measurement and reality.
standard cosmological model has been established, precision tests have been performed, cosmological
parameters of the model are measured with ~1% precision. Sophisticated statistical techniques have been developed to analyse these data sets and reach these
remarkable achievements. The next challenge cosmology has to meet is to enter the era of accuracy. The
precision of a measurement, indicated by the number of significant figures, accounts for statistical errors.
Accuracy quantifies the closeness of the measurement of a quantity to that quantity's true value, which is
the realm of systematic errors. Accuracy is the new precision.Forthcoming observational effort promise to achieve major
advances in answering a number of big questions, with deep links to fundamental physics: unveil the nature
of dark energy, shed light on dark matter, measure the neutrino mass, understand the mechanism driving
cosmological inflation etc. The path towards answering these questions is a challenging one. The analysis
and interpretation of the data (if not also the survey planning) will need to be revisited in light of the
unprecedented precision enabled by the new data. How can accuracy keep up with increased precision?
Precision without accuracy is dangerous, as highly significant (but wrong) results may be inferred. How can
we make sure that the systematic error budget is known and safely below the statistical error?
Without an effective treatment of
systematic errors (from mitigation to full accounting) the power of the next generation cosmological surveys
will be seriously compromised. I propose to face this challenge by developing a comprehensive
treatment of systematic errors with the goal to minimize, uncover, quantify and account for
otherwise unknown differences between the interpretation of a measurement and reality.
I have contributed to clarify, understand, quantify, and interpret the consequences of the Hubble tension in cosmology.
As the basic cosmological parameters of the standard cosmological model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. There is increasing evidence for discrepancies between determinations of the current expansion rate of the Universe, the Hubble constant. This is a wonderful real world case where to apply developments along the lines of the proposed work.
With my group I am developing a blinding strategy for galaxy surveys that can be applied at the catalog level. This will protect from experimenter's bias. The methodology works very well and has been tested on mock surveys. This reflects one of the goals of the proposal.
The group and I have been exploring the impact and importance of effects at the largest scales: if ignored there effects might bias the cosmological interpretation of our observations and we might ignore a key window into new physics.
We have also provided a procedure to interpret correctly the measurement of neutrino masses from forthcoming surveys, eliminating systematic effects that would mask the true value of the neutrino mass.
The two points above are well in line with the goals of the proposal.
As the basic cosmological parameters of the standard cosmological model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. There is increasing evidence for discrepancies between determinations of the current expansion rate of the Universe, the Hubble constant. This is a wonderful real world case where to apply developments along the lines of the proposed work.
With my group I am developing a blinding strategy for galaxy surveys that can be applied at the catalog level. This will protect from experimenter's bias. The methodology works very well and has been tested on mock surveys. This reflects one of the goals of the proposal.
The group and I have been exploring the impact and importance of effects at the largest scales: if ignored there effects might bias the cosmological interpretation of our observations and we might ignore a key window into new physics.
We have also provided a procedure to interpret correctly the measurement of neutrino masses from forthcoming surveys, eliminating systematic effects that would mask the true value of the neutrino mass.
The two points above are well in line with the goals of the proposal.
The approach developed will be key in developing and implementing a robust and reliable interpretation of forthcoming data. We expect to continue in this direction and to generalise the approaches we have developed so far in a unified framework, as outlines in the proposal.