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TauCeti.NumberTheory.ArithmeticDirichletSeries.Prime.Psi

Chebyshev's ฯˆ for a set of prime ideals, and the removal of the higher prime powers #

For a set S of height-one primes of the ring of integers of a number field K, Chebyshev's ฯˆ weights every prime power ๐”ญ ^ k with ๐”ญ โˆˆ S and k โ‰ฅ 1 by log N(๐”ญ), while ฯ‘ weights only the primes themselves. This file defines ฯˆ, proves that the difference ฯˆ - ฯ‘ is exactly the higher-prime-power sum estimated in TauCeti/NumberTheory/ArithmeticDirichletSeries/HigherPrimePowers.lean, and spends that estimate on the transfer of an asymptotic ฯˆ(x) = ฮด x + o(x) to ฯ‘(x) = ฮด x + o(x).

Prime powers with k โ‰ฅ 2 are kept visible throughout: ฯˆ is defined with all of them present, and their removal is a named hypothesis, TauCeti.HasNegligibleHigherPrimePowers, discharged for the standard logarithmic weight by TauCeti.standardPrimePowerRemoval. A different coefficient system does not get that hypothesis for free; what it has to supply is the domination bound of TauCeti.primePowerSummatory_isLittleO_of_le_higherPrimePowerWeight.

Main definitions #

Main results #

Roadmap role #

This is Layer 10.2 of TauCetiRoadmap/ArithmeticDirichletSeries/README.md: "For the fixed standard nonnegative logarithmic prime-power weight, use Layer 5 to prove standardPrimePowerRemoval : HasNegligibleHigherPrimePowers K S and make primeTheta_asymptotic_of_primePsi consume that named estimate." It also supplies the arithmetic half of Layer 10.1, "Define primePsi with all prime powers present": the exact nonnegative von Mangoldt coefficient system and the identity presenting ฯˆ as its partial sum, which is the shape in which a Tauberian theorem delivers its conclusion. The analytic boundary package and the resulting prime-number-theorem transfer are in TauCeti/NumberTheory/ArithmeticDirichletSeries/Prime/Boundary.lean.

References #

The rational-prime case of ฯˆ, ฯ‘ and their difference is Mathlib's Mathlib/NumberTheory/Chebyshev.lean, whose Chebyshev.theta_le_psi and Chebyshev.abs_psi_sub_theta_le_sqrt_mul_log are the analogues of TauCeti.primeTheta_le_primePsi and TauCeti.standardPrimePowerRemoval; nothing is transported from there, since the estimate consumed here is proved over prime ideals in Layer 5.

The standard logarithmic prime-power weight #

noncomputable def TauCeti.primePowerWeight {K : Type u_1} [Field K] [NumberField K] (A : IdealPrimePower K) :

The standard logarithmic prime-power weight: the value log N(๐”ญ) at the prime power ๐”ญ ^ k, for every k โ‰ฅ 1. Unlike TauCeti.higherPrimePowerWeight it does not vanish on the primes themselves, so its summatory function is Chebyshev's ฯˆ rather than ฯˆ - ฯ‘.

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    The standard logarithmic prime-power weight is the real part of the ideal von Mangoldt function of Layer 2, restricted to the prime powers.

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    On a prime-power ideal the ideal von Mangoldt function is the standard logarithmic weight, as a complex number.

    The standard logarithmic prime-power weight is positive.

    The standard logarithmic prime-power weight is nonnegative.

    @[simp]

    On a prime the standard weight is the logarithm of its own absolute norm.

    Away from the primes the two prime-power weights agree: TauCeti.higherPrimePowerWeight is the standard weight with its exponent-one part deleted.

    Chebyshev's ฯˆ #

    Chebyshev's ฯˆ for a set of prime ideals: the inclusive sum of log N(๐”ญ) over the prime powers ๐”ญ ^ k of absolute norm at most x whose base ๐”ญ lies in S, with every exponent k โ‰ฅ 1 present.

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      Chebyshev's ฯˆ as an explicit sum over the inclusive prime-power carrier.

      @[simp]
      theorem TauCeti.primePsi_empty {K : Type u_1} [Field K] [NumberField K] (x : โ„) :

      The empty set of primes contributes nothing to ฯˆ.

      Chebyshev's ฯˆ is nonnegative.

      Chebyshev's ฯˆ is monotone in the inclusive cutoff.

      Below the cutoff 2 there is no prime power to weight.

      The higher prime powers as the gap between ฯˆ and ฯ‘ #

      Splitting the exponent-one part off a restricted prime-power sum. For a set T of prime powers containing exactly the primes of S, the summatory function of the standard logarithmic weight restricted to T exceeds ฯ‘ by the higher-prime-power sum over T.

      The difference between ฯˆ and ฯ‘ is the higher-prime-power sum. Both sides run over the prime powers whose base lies in S; the exponent-one part of ฯˆ is exactly ฯ‘.

      Chebyshev's ฯ‘ never exceeds ฯˆ.

      Removing the higher prime powers #

      The higher prime powers of S are negligible: ฯˆ - ฯ‘ is o(x). Naming the hypothesis keeps the estimate an input to the prime-number-theorem transfer instead of a definitional simplification of ฯˆ.

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        Removal of the higher prime powers for the standard logarithmic weight. This is the o(x) corollary of the Layer 5 bound ฯˆ(x) - ฯ‘(x) โ‰ค [K:โ„š] / (2 log 2) ยท โˆšx logยฒ x.

        For x โ‰ฅ 1, a finite set of primes contributes at most #S ยท log x to ฯˆ. Fibring over the prime base, the exponents k โ‰ฅ 1 with N(๐”ญ) ^ k โ‰ค x contribute at most log x in total for each of the finitely many ๐”ญ.

        A counting argument can therefore discard a finite exceptional set of primes โ€” those ramifying in an extension, say, or lying above such โ€” at a cost of O(log x).

        The fibre step is TauCeti.card_mul_log_absNorm_le_of_pow_le_of_base_eq, which bounds the total weight of the prime powers over a single base by log x.

        A finite set of primes is O(log x) for ฯˆ, the asymptotic form of the bound above.

        A finite set of primes is negligible for ฯˆ, the form the total discard estimate sums.

        theorem TauCeti.primeTheta_asymptotic_of_primePsi {K : Type u_1} [Field K] [NumberField K] {S : Set (IsDedekindDomain.HeightOneSpectrum (NumberField.RingOfIntegers K))} {ฮด : โ„} (h : HasNegligibleHigherPrimePowers K S) (hฯˆ : (fun (x : โ„) => primePsi K S x - ฮด * x) =o[Filter.atTop] fun (x : โ„) => x) :
        (fun (x : โ„) => primeTheta K S x - ฮด * x) =o[Filter.atTop] fun (x : โ„) => x

        Transfer of a linear asymptotic from ฯˆ to ฯ‘. If the higher prime powers of S are negligible and ฯˆ(x) = ฮด x + o(x), then ฯ‘(x) = ฮด x + o(x).

        theorem TauCeti.primePsi_asymptotic_of_primeTheta {K : Type u_1} [Field K] [NumberField K] {S : Set (IsDedekindDomain.HeightOneSpectrum (NumberField.RingOfIntegers K))} {ฮด : โ„} (h : HasNegligibleHigherPrimePowers K S) (hฯ‘ : (fun (x : โ„) => primeTheta K S x - ฮด * x) =o[Filter.atTop] fun (x : โ„) => x) :
        (fun (x : โ„) => primePsi K S x - ฮด * x) =o[Filter.atTop] fun (x : โ„) => x

        Transfer of a linear asymptotic from ฯ‘ to ฯˆ, the converse direction.

        The asymptotic-equivalence form of TauCeti.primeTheta_asymptotic_of_primePsi, for a nonzero density ฮด. At ฮด = 0 an equivalence would force ฯ‘ to vanish eventually, so the o(x) form above is the one that covers that case.

        The von Mangoldt coefficient system of a set of primes #

        The von Mangoldt weight of a set S of height-one primes, as a real weight on the nonzero integral ideals of ๐“ž K: the value log N(๐”ญ) at ๐”ญ ^ k for ๐”ญ โˆˆ S and k โ‰ฅ 1, and 0 at every other nonzero ideal.

        It is the ideal von Mangoldt function of Layer 2 cut down to the prime powers whose base lies in S, taken in its real form, because the Tauberian input of Layer 9 is a nonnegative real coefficient system. Cutting down by "some prime of S divides A" rather than by the prime base of A avoids naming that base at ideals which are not prime powers, where the ideal von Mangoldt function vanishes anyway.

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          At an ideal divisible by a prime of S, the von Mangoldt weight of S is the ideal von Mangoldt value.

          The von Mangoldt weight of S vanishes at an ideal with no prime factor in S.

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          The empty set of primes carries no von Mangoldt weight.

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          The von Mangoldt weight of S vanishes away from the prime-power ideals.

          The von Mangoldt weight of S at a positive power of a prime of S.

          theorem TauCeti.primeVonMangoldtWeight_of_pow_of_notMem {K : Type u_1} [Field K] [NumberField K] {S : Set (IsDedekindDomain.HeightOneSpectrum (NumberField.RingOfIntegers K))} {๐”ญ : IsDedekindDomain.HeightOneSpectrum (NumberField.RingOfIntegers K)} (h๐”ญ : ๐”ญ โˆ‰ S) {k : โ„•} (hk : 0 < k) {A : โ†ฅ(nonZeroDivisors (Ideal (NumberField.RingOfIntegers K)))} (hA : ๐”ญ.asIdeal ^ k = โ†‘A) :

          The von Mangoldt weight of S vanishes at a positive power of a prime outside S.

          The von Mangoldt weight is monotone in the set of primes.

          The von Mangoldt weight of S on the prime-power carrier is exactly the summand of Chebyshev's ฯˆ: the standard logarithmic weight at the prime powers with base in S, and 0 elsewhere.

          @[simp]

          Over all height-one primes the weight is the real form of the ideal von Mangoldt function of Layer 2.

          The von Mangoldt coefficient system of a set S of height-one primes: its value at n is the sum of log N(๐”ญ) over the prime powers ๐”ญ ^ k of absolute norm exactly n whose base ๐”ญ lies in S.

          This is the nonnegative arithmetic function whose inclusive partial sums are Chebyshev's ฯˆ, by TauCeti.primePsi_eq_sum_range, and whose Dirichlet series is the one a Tauberian theorem sees.

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            The von Mangoldt coefficient at n is the total weight of the absolute-norm fibre at n.

            The von Mangoldt coefficients are nonnegative, as the Tauberian input requires.

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            The empty set of primes has vanishing von Mangoldt coefficients.

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            The von Mangoldt coefficient at 1 vanishes: the unit ideal is the only ideal of absolute norm one, and it is not a prime power.

            The von Mangoldt coefficients are monotone in the set of primes.

            The support of the coefficient system: a von Mangoldt coefficient vanishes unless its index is a prime power, since the absolute norm of a prime-power ideal is again a prime power.

            The coefficient system is the Layer 1 norm regrouping of the von Mangoldt weight of S, read in โ„‚.

            Over all height-one primes the coefficient system regroups the ideal von Mangoldt function of Layer 2 by absolute norm.

            Chebyshev's ฯˆ is the inclusive partial sum of the von Mangoldt coefficient system.

            This is what lets a Tauberian theorem stated for xโปยน โˆ‘_{n โ‰ค x} a n speak about ฯˆ(x) / x: Layer 9's conclusion is about the left-hand side, and Layer 10 needs it about the right.

            Chebyshev's ฯˆ at a natural cutoff, the form in which the coefficient system is summed.

            Over โ„š, the von Mangoldt coefficients of any set of primes are bounded by ฮ›.