Shear viscosity in neutron star cores

Understand

We calculate the shear viscosity $\eta = \eta_{e\mu}+\eta_{n}$ in a neutron star core composed of nucleons, electrons and muons ($\eta_{e\mu}$ being the electron-muon viscosity, mediated by collisions of electrons and muons with charged particles, and $\eta_{n}$ the neutron viscosity, mediated by neutron-neutron and neutron-proton collisions).

• Deriving $\eta_{e\mu}$, we take into account the Landau damping in collisions of electrons and muons with charged particles via the exchange of transverse plasmons.
• It lowers $\eta_{e\mu}$ and leads to the non-standard temperature behavior $\eta_{e\mu}\propto T^{-5/3}$.
• The viscosity $\eta_{n}$ is calculated taking into account that in-medium effects modify nucleon effective masses in dense matter.