# 1.2.9. Discworld¶

Several complicated astrophysical environments can be simplified to discworlds.

## 1.2.9.1. Neutron Star Mergers and Accretion Discs¶

In the paper [Wu2017], they discussed the breaking of mirror symmetry.

Mirror Symmetry

Mirror symmetry in [Wu2017] is the symmetry of reflection with respect to y axis, i.e., symmetry for coordinate $$x$$ and $$-x$$.

Fig. 1.169 Geometry in [Wu2017]. Mirror symmetry corresponds to the symmetry of spectrum in $$\phi$$. The ELN (electron lepton number) distribution is symmetric for $$\phi\to -\phi$$.

In the polarization tensor, $$v^1$$ is related to the so called Mirror symmetry. We expect the dispersion relation related to $$\Pi_{22}$$ to be related to the mirror symmetry.

## 1.2.9.2. References and Notes¶

 [Wu2017] (1, 2, 3) Wu, M.-R., & Tamborra, I. (2017). Fast neutrino conversions: Ubiquitous in compact binary merger remnants, 1–7. arXiv:1701.06580.

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