k-cut Cosmic Shear: Tunable Power Spectrum Sensitivity to Test Gravity

TL;DR

This paper introduces a tunable method to reduce small-scale sensitivity in cosmic shear measurements, improving robustness against modeling uncertainties and aiding tests of gravity and dark energy.

Contribution

It proposes a redshift-dependent l-cut combined with BNT nulling to isolate large-scale information, enhancing the reliability of cosmic shear analyses.

Findings

Effective removal of small-scale sensitivity demonstrated

Improved constraints on dark energy parameters shown

Method offers a computationally efficient alternative to simulations

Abstract

If left unchecked modeling uncertainties at small scales, due to poorly understood baryonic physics and non-linear structure formation, will significantly bias Stage IV cosmic shear two-point statistic parameter constraints. While it is perhaps possible to run N-body or hydrodynamical simulations to determine the impact of these effects this approach is computationally expensive; especially to test a large number of theories of gravity. Instead we propose directly removing sensitivity to small-scale structure from the lensing spectrum, creating a statistic that is robust to these uncertainties. We do this by taking a redshift-dependent l-cut after applying the Bernardeau-Nishimichi-Taruya (BNT) nulling scheme. This reorganizes the information in the lensing spectrum to make the relationship between the angular scale, l, and the structure scale, k, much clearer compared to standard cosmic shear power spectra -- for which no direct relationship exists. We quantify the effectiveness of this method at removing sensitivity to small scales and compute the predicted Fisher error on the dark energy equation of state, w0, for different k-cuts in the matter power spectrum.