# Cosmology with Strong Lensing Systems

**Authors:** Shuo Cao, Marek Biesiada, Raphaël Gavazzi, Aleksandra Piórkowska, Zong-Hong Zhu  
**arXiv:** [1509.07649](https://arxiv.org/abs/1509.07649)  
**Date:** 2015-09-25  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/1509.07649v1/

## Key points

- Authors present a comprehensive analysis of 118 strong gravitational lensing systems from various surveys
- Main objective is to constrain the cosmic equation of state using these lensing systems
- Two different cases of dark energy phenomenology explored: $XCDM$ model and CPL parametrization
- Spherically symmetric mass distribution assumed in lensing galaxies, with consideration for evolving power-law index ($\gamma(z)$)
- Results for $XCDM$ cosmology show agreement with previous research on $w$ and $\gamma$
- Jointly constraining CPL parameters and $\gamma(z)$ leads to significantly better confidence regions than previous studies
- Strong gravitational lensing systems have potential for probing cosmological parameters such as dark energy's equation of state and its evolution over time
- Study confirms previous findings and provides more accurate and precise results
- Opens up new avenues for future research in cosmology using strong gravitational lensing systems

## Summary

In the paper "Cosmology with Strong Lensing Systems," authors Shuo Cao, Marek Biesiada, Raphaël Gavazzi, Aleksandra Piórkowska, and Zong-Hong Zhu present a comprehensive analysis of 118 strong gravitational lensing systems from SLACS, BELLS, LSD, and SL2S surveys. The main objective of their study is to constrain the cosmic equation of state using these lensing systems. The authors explore two different cases of dark energy phenomenology: the $XCDM$ model and the Chevalier-Polarski-Linder (CPL) parametrization. In the $XCDM$ model, dark energy is represented by a fluid with a constant equation of state parameter ($w$). On the other hand, in the CPL parametrization, $w$ is allowed to evolve with redshift according to $w(z) = w_0 + w_1 \frac{z}{1+z}$. To analyze these lensing systems, the authors assume a spherically symmetric mass distribution in lensing galaxies and relax the rigid assumption of a singular isothermal sphere (SIS) model by considering a more general power-law index ($\gamma$), which can also evolve with redshifts ($\gamma(z)$). The results obtained for the $XCDM$ cosmology show agreement with values previously obtained by other researchers regarding both $w$ and $\gamma$ parameters. Additionally, they go further and jointly constrain the CPL parameters along with $\gamma(z)$, resulting in significantly better confidence regions than those obtained through similar methods in previous studies. Furthermore, these confidence regions exhibit a complementary trend to supernova Ia data which suggests that strong gravitational lensing systems have great potential for probing cosmological parameters such as dark energy's cosmic equation of state and whether it evolves over time. In conclusion, this paper demonstrates how useful strong gravitational lensing systems are in understanding and constraining cosmological parameters. Not only do its results confirm previous findings but they also provide more accurate and precise ones. This study opens up new avenues for future research in cosmology using strong gravitational lensing systems.