= Degenerate-plasma dielectric response
{title2=$\epsilon=1+\frac{3\omega_p^2}{k^2v_F^2}\left[1-\frac{s}{2}\log\frac{s+1}{s-1}\right],\quad s=\frac{\omega}{kv_F}>1$}
For an isotropic completely degenerate nonrelativistic <Fermi gas> in classical-trajectory collisionless <kinetic theory>, the parallel <marginal distribution> is $F(u)=3n(v_F^2-u^2)\mathbf1_{|u|<v_F}/(4v_F^3)$. Integrating $F'(u)/(u-\omega/k)$ yields the electron <dielectric function> in the title for fixed ions. Its real roots outside the occupied interval have no <Landau damping>. Quantum recoil, collisions and finite-temperature tails require an enlarged model.
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