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MathlibNt.SieveTheory.LinearSieve.JurkatRichert.JurkatRichert1965ChenDelayFunctions

The Jurkat--Richert delay functions by finite method of steps #

We construct the weighted functions u F(u) and u f(u) from constant initial data, rather than postulating a delay-equation contract. Each finite approximant is continuous and the approximants stabilize on successively larger half-lines. The harmless cutoffs below extend the weighted functions to the whole real line; the sieve functions themselves are used only on the positive half-line.

The normalization is (5.5), and the integral and differential recurrences are (5.7) and (5.6) of Jurkat--Richert (1965). No asymptotic estimates are asserted.

false selects the upper function; true selects the lower function.

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    Finite method of steps for the weighted pair. The denominator is truncated only outside the domain of integration, where its value is immaterial.

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      theorem MathlibNt.SieveTheory.JurkatRichert1965ChenGammaOneQOne.delayStep_succ_eq (A : ) (n : ) (b : Bool) {u : } (hu : u n + 2) :
      delayStep A (n + 1) b u = delayStep A n b u

      One more step does not change the solution on the already constructed range.

      theorem MathlibNt.SieveTheory.JurkatRichert1965ChenGammaOneQOne.delayStep_eq_of_le (A : ) {n m : } (hnm : n m) (b : Bool) {u : } (hu : u n + 2) :
      delayStep A m b u = delayStep A n b u

      A globally defined weighted function, requiring only finitely many integrals at any argument. The ceiling is only a choice of a sufficiently large step.

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        Any sufficiently advanced finite step computes the global function exactly.

        The globally continuous delayed integrand, including an irrelevant extension to the left of the initial endpoint.

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          The global integral equation, proved by stabilization, not assumed.

          Formula (5.7), for the explicitly constructed pair.

          The right derivative at the initial endpoint, included in (5.6).

          The literal weighted differential equation (5.6) away from the endpoint.

          theorem MathlibNt.SieveTheory.JurkatRichert1965ChenGammaOneQOne.delayFunction_unique (A : ) (k : Bool) (hinit : ∀ (b : Bool) (u : ), 0 < uu 2k b u = delayInitial A b / u) (hint : ∀ (b : Bool) (u : ), 2 uu * k b u = delayInitial A b + (t : ) in 2..u, k (!b) (t - 1)) (b : Bool) (u : ) :
          0 < uk b u = delayFunction A b u

          Uniqueness of the integral initial-value problem on the positive half-line. This is a consequence of the construction, not an input to it.

          The first extended upper formula, Jurkat--Richert (5.8).

          theorem MathlibNt.SieveTheory.JurkatRichert1965ChenGammaOneQOne.jr1965g_integral_recurrence (ν : ) {v u : } (hv : 2 v) (hvu : v u) :
          u * jr1965g ν u = v * jr1965g ν v + (t : ) in v..u, jr1965g (ν + 1) (t - 1)
          theorem MathlibNt.SieveTheory.JurkatRichert1965ChenGammaOneQOne.hasDerivAt_mul_jr1965g (ν : ) {u : } (hu : 2 < u) :
          HasDerivAt (fun (x : ) => x * jr1965g ν x) (jr1965g (ν + 1) (u - 1)) u