theorem convergence_rate_cubic {k : ℕ} (hk : 2 ≤ k) (L : ℕ) (a₀ : ℝ) :
|modeAfterL k 3 L a₀| ≤ |a₀| := by
simp only [modeAfterL, abs_mul]
have ⟨hpos, hlt⟩ := modeRate_in_unit_interval hk (le_refl 3)
have hle : modeRate k 3 ^ L ≤ 1 := pow_le_one₀ hpos.le hlt.le
calc |modeRate k 3 ^ L| * |a₀|
= modeRate k 3 ^ L * |a₀| := by
rw [abs_of_nonneg (pow_nonneg hpos.le L)]
_ ≤ 1 * |a₀| :=
mul_le_mul_of_nonneg_right hle (abs_nonneg a₀)
_ = |a₀| := one_mul _Aggregation-invariant class results from Paper 1, Section 5: