# Evolution of bare quark stars in full general relativity: Single star case

**Authors:** Enping Zhou, Kenta Kiuchi, Masaru Shibata, Antonios Tsokaros, Koji Uryu  
**arXiv:** [2105.07498](https://arxiv.org/abs/2105.07498)  
**Date:** 2021-05-16  
**Summary page:** https://www.summarizepaper.com/en/paper/2105.07498v1/

## Key points

- Evolution of bare quark stars in numerical relativity simulations
- Modifications to the primitive recovery procedure
- Reliability and convergence of the implementation demonstrated
- Evolution of triaxially rotating quark star models with different masses
- Analysis of gravitational-wave emission from triaxially rotating quark stars
- Investigation of mass ejection phenomenon in differentially rotating quark stars
- Supramassive quark stars are unlikely to be significant sources of continuous gravitational waves
- Rapid decay of gravitational-wave amplitude within a timescale of 10 milliseconds for more massive models
- Confirmation that quark stars can undergo non-axisymmetric instabilities similar to neutron stars
- Occurrence of non-axisymmetric instabilities with relatively small degrees of differential rotation

## Summary

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This study focuses on the evolution of bare quark stars in numerical relativity simulations, specifically addressing the modifications made to the primitive recovery procedure. The authors demonstrate the reliability and convergence of their implementation by evolving two triaxially rotating quark star models with different masses, as well as a differentially rotating quark star model that is dynamically unstable due to its large kinetic energy. Through these simulations, the researchers are able to verify that their method effectively resolves the evolution of the discontinuous surface of quark stars and potential mass ejection from them. They also investigate the evolution of triaxial deformation and analyze the properties of gravitational-wave emission from triaxially rotating quark stars. Additionally, they examine the mass ejection phenomenon in the case of differentially rotating quark stars. The findings indicate that supramassive quark stars are unlikely to be significant sources of continuous gravitational waves. This is because these stars recover axisymmetry at a much faster rate compared to models with smaller masses, resulting in a rapid decay of gravitational-wave amplitude within a timescale of 10 milliseconds. However, it should be noted that while more massive models exhibit larger instantaneous amplitudes, they still experience a similar decay pattern. Furthermore, this study confirms previous indications that quark stars can undergo non-axisymmetric instabilities similar to neutron stars. However, these instabilities occur with relatively small degrees of differential rotation, aligning with expectations based on earlier initial data studies. In summary, this research provides valuable insights into the behavior and characteristics of bare quark stars in full general relativity simulations. The modifications made to the primitive recovery procedure enable accurate resolution of their surface evolution and potential mass ejection phenomena. The study's findings contribute to our understanding of gravitational-wave emission from triaxially rotating quark stars and confirm the occurrence of non-axisymmetric instabilities in these objects under specific conditions.