Eisenstein layers of Lubin–Tate torsion (source code)

= Eisenstein layers of Lubin–Tate torsion

For $f(X)=\pi X+X^q$ and its iterates $f_n$, the quotient
$$
\Phi_n(X)=\frac{f_n(X)}{f_{n-1}(X)}
=\pi+f_{n-1}(X)^{q-1}
$$
is Eisenstein. A nonzero root of exact level $n$ therefore generates a totally ramified separable extension.