English
For a LieModule homomorphism f, the image of the k-th lower central series is contained in the k-th lower central series of the target.
Русский
Гомоморфизм f сохраняет нижнюю центральную серию на каждом уровне: map(lcs_k(M)) ≤ lcs_k(M₂).
LaTeX
$$(lowerCentralSeries(R,L,M,k)).map f ≤ lowerCentralSeries(R,L,M₂,k)$$
Lean4
theorem map_lowerCentralSeries_le (f : M →ₗ⁅R,L⁆ M₂) :
(lowerCentralSeries R L M k).map f ≤ lowerCentralSeries R L M₂ k := by
induction k with
| zero => simp only [lowerCentralSeries_zero, le_top]
| succ k ih =>
simp only [LieModule.lowerCentralSeries_succ, LieSubmodule.map_bracket_eq]
exact LieSubmodule.mono_lie_right ⊤ ih