Testing Cosmology with Double Source Lensing

TL;DR

This paper explores how double source lensing can test fundamental cosmological principles like spatial curvature and distance duality, providing new consistency equations and forecasting constraints on dark energy and lens profiles.

Contribution

It derives a new consistency equation for constant spatial curvature and analyzes the precision needed to test the distance duality relation using double source lensing.

Findings

Derived a consistency equation for spatial curvature testing.

Showed that lens mass profile evolution must be tightly constrained for distance duality tests.

Forecasted constraints on dark energy parameters using Euclid and LSST data.

Abstract

Double source lensing provides a dimensionless ratio of distance ratios, a "remote viewing" of cosmology through distances relative to the gravitational lens, beyond the observer. We use this to test the cosmological framework, particularly with respect to spatial curvature and the distance duality relation. We derive a consistency equation for constant spatial curvature, allowing not only the investigation of flat vs curved but of the Friedmann-Lema\^itre-Robertson-Walker framework itself. For distance duality, we demonstrate that the evolution of the lens mass profile slope must be controlled to $\gtrsim5$ times tighter fractional precision than a claimed distance duality violation. Using LENSPOP forecasts of double source lensing systems in Euclid and LSST surveys we also explore constraints on dark energy equation of state parameters and any evolution of the lens mass profile slope.