Testing dark energy paradigms with weak gravitational lensing

TL;DR

This paper develops a method to test dark energy models using weak gravitational lensing data, predicting expected signals in LambdaCDM and identifying how future observations can falsify these models.

Contribution

It introduces a framework to compare observed cosmic shear spectra with model predictions based on existing constraints, allowing for falsification of LambdaCDM and quintessence models.

Findings

Predicted lensing spectra for LambdaCDM match current constraints.

Future excess lensing observations can falsify LambdaCDM and all quintessence models.

Uncertainties in nonlinear matter power spectrum affect model falsifiability.

Abstract

Any theory invoked to explain cosmic acceleration predicts consistency relations between the expansion history, structure growth, and all related observables. Currently there exist high-quality measurements of the expansion history from Type Ia supernovae, the cosmic microwave background temperature and polarization spectra, and baryon acoustic oscillations. We can use constraints from these datasets to predict what future probes of structure growth should observe. We apply this method to predict what range of cosmic shear power spectra would be expected if we lived in a LambdaCDM universe, with or without spatial curvature, and what results would be inconsistent and therefore falsify the model. Though predictions are relaxed if one allows for an arbitrary quintessence equation of state $-1\le w(z)\le 1$, we find that any observation that rules out LambdaCDM due to excess lensing will also rule out all quintessence models, with or without early dark energy. We further explore how uncertainties in the nonlinear matter power spectrum, e.g. from approximate fitting formulas such as Halofit, warm dark matter, or baryons, impact these limits.