English
Same as above: χ convolved with χ·μ equals δ.
Русский
То же самое: свертка χ с χ·μ дают δ.
LaTeX
$$$(\chi \cdot) * (\chi \cdot \mu) = \delta.$$$
Lean4
/-- The L-series of the twist of `f` by a Dirichlet character converges at `s` if the L-series
of `f` does. -/
theorem LSeriesSummable_mul {N : ℕ} (χ : DirichletCharacter ℂ N) {f : ℕ → ℂ} {s : ℂ} (h : LSeriesSummable f s) :
LSeriesSummable (↗χ * f) s :=
by
refine .of_norm <| h.norm.of_nonneg_of_le (fun _ ↦ norm_nonneg _) fun n ↦ norm_term_le s ?_
simpa using mul_le_of_le_one_left (norm_nonneg <| f n) <| χ.norm_le_one n