theorem
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zeta_isMultiplicative
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IndisputableMonolith.NumberTheory.Primes.ArithmeticFunctions on GitHub at line 231.
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228 simp only [zeta, ArithmeticFunction.zeta_apply, ↓reduceIte]
229
230/-- ζ is multiplicative. -/
231theorem zeta_isMultiplicative : ArithmeticFunction.IsMultiplicative zeta := by
232 simp only [zeta]
233 exact ArithmeticFunction.isMultiplicative_zeta
234
235/-! ### Möbius inversion fundamentals -/
236
237/-- The key identity: μ * ζ = ε (the Dirichlet identity).
238This is the foundation of Möbius inversion. -/
239theorem moebius_mul_zeta : (mobius : ArithmeticFunction ℤ) * ↑zeta = 1 := by
240 simp only [mobius, zeta]
241 exact ArithmeticFunction.moebius_mul_coe_zeta
242
243/-- Symmetric form: ζ * μ = ε. -/
244theorem zeta_mul_moebius : (↑zeta : ArithmeticFunction ℤ) * mobius = 1 := by
245 simp only [mobius, zeta]
246 exact ArithmeticFunction.coe_zeta_mul_moebius
247
248/-- For the identity (Dirichlet unit), we wrap ε = δ_1. -/
249abbrev dirichletOne : ArithmeticFunction ℤ := 1
250
251@[simp] theorem dirichletOne_def : dirichletOne = 1 := rfl
252
253/-- ε(1) = 1. -/
254theorem dirichletOne_one : dirichletOne 1 = 1 := by
255 simp [dirichletOne]
256
257/-- ε(n) = 0 for n > 1. -/
258theorem dirichletOne_ne_one {n : ℕ} (hn : n ≠ 1) : dirichletOne n = 0 := by
259 simp [dirichletOne, hn]
260
261/-! ### Additional multiplicativity lemmas -/