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Do stochastic inhomogeneities affect dark-energy precision measurements?
I Ben-Dayan1, M Gasperini, G Marozzi
1Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, Ontario M5S 3H8, Canada.
Physical Review Letters
|February 7, 2013
Summary
Cosmological perturbations do not mimic dark energy. Precision measurements of dark energy parameters using luminosity distance are affected by a few-percent statistical error due to stochastic variance.
Area of Science:
- Cosmology
- Astrophysics
- General Relativity
Background:
- The luminosity-redshift relation is a key tool for understanding the expansion history of the universe and the nature of dark energy.
- Cosmological perturbations, while essential for structure formation, can potentially affect cosmological measurements.
- Quantifying the impact of these perturbations is crucial for accurate cosmological parameter estimation.
Purpose of the Study:
- To compute the effect of a stochastic background of cosmological perturbations on the luminosity-redshift relation to second order.
- To investigate whether these perturbations can mimic dark energy.
- To identify the optimal method for precision estimates of dark energy parameters.
Main Methods:
- A covariant and gauge-invariant light-cone averaging procedure was employed.
- The computation was performed to second order in cosmological perturbations.
- Different averaging functions for luminosity distance were analyzed.
Main Results:
- The derived expressions for the luminosity-redshift relation are free from ultraviolet and infrared divergences.
- Cosmological perturbations at second order cannot account for a significant fraction of dark energy.
- The energy flux, minimally affected by perturbations at large redshift (z), is proposed as the best observable for precision dark energy studies.
Conclusions:
- Stochastic background of cosmological perturbations does not mimic dark energy.
- Precision estimates of dark energy parameters are achievable, but irreducible stochastic variance introduces a few-percent statistical error.
- The choice of averaging function for luminosity distance is critical for minimizing systematic uncertainties.
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