Strongly gravitational lensed SNe Ia as multi-messengers: Direct test of the Friedmann-Lema\^{\i}tre-Robertson-Walker metric

TL;DR

This paper proposes a novel method to directly test the Friedmann-Lemaître-Robertson-Walker metric using multiple measurements of strongly lensed Type Ia supernovae, enabling model-independent constraints on the universe's spatial curvature.

Contribution

It introduces a new observational approach utilizing galactic-scale strong lensing of SNe Ia to test the FLRW metric directly, independent of matter content assumptions.

Findings

Hundreds of lensed SNe Ia can constrain spatial curvature to ΔΩ_k=0.04

Method provides model-independent measurements of curvature

Constraints are comparable to Planck 2015 results

Abstract

We present a new idea of testing the validity of the Friedman-Lema\^{\i}tre-Robertson-Walker metric, through the multiple measurements of galactic-scale strong gravitational lensing systems with type Ia supernovae in the role of sources. Each individual lensing system will provide a model-independent measurement of the spatial curvature parameter referring only to geometrical optics independently of the matter content of the universe. This will create a valuable opportunity to test the FLRW metric directly. Our results show that with hundreds of strongly lensed SNe Ia observed by LSST, one would produce robust constraints on the spatial curvature with accuracy $\Delta \Omega_k=0.04$ comparable to the Planck 2015 results.