Fit-free pipeline computation of the shear viscosity of pure neutron matter: Quantum enhancement, Fermi-liquid turnover, and in-medium corrections

We deliver a fit-free computational pipeline — no stage adjusted to any observable — from a single fixed nucleon–nucleon potential to a simulation-ready shear-viscosity table η(T,n) of pure neutron matter, spanning the non-degenerate to degenerate regimes under fourteen machine-checked acceptance gates. Three findings. At neutron-star-crust temperatures (1–10 MeV), quantum diffraction enhances the viscosity over the classical value by factors 4.34–3.16, the quantum-to-classical ratio crossing unity near 92 MeV. With Pauli blocking, the T^0.75 growth law and the degenerate T⁻² law (measured slope −1.835) join near the Fermi temperature into a rise-then-fall turnover — the textbook Fermi-liquid morphology reproduced without fitting. In-medium corrections act through a verified 1/m*² mechanism, modifying the table by up to 48.9% while the T⁻² exponent stays intact (slope drift 0.0285). The delivered table v1.1 covers n = 0.5–2 n₀ and T = 0.5–100 MeV; the ratio η/s exceeds the KSS bound everywhere, at minimum 38-fold, placing pure neutron matter at the rheological extreme opposite to the quark–gluon plasma. The absolute values are potential-dependent (the input is an unfitted model potential with a positive ¹S₀ scattering length); the structural conclusions are robust, and the pipeline accepts any fixed NN potential as-is.