9 Secondary explicit estimates
9.1 Definitions
In this section we define the basic types of secondary estimates we will work with in the project.
\(\pi (x)\) is the number of primes less than or equal to \(x\).
\(\mathrm{li}(x) = \int _0^x \frac{dt}{\log t}\) (in the principal value sense) and \(\mathrm{Li}(x) = \int _2^x \frac{dt}{\log t}\).
For \(t {\gt} -1\), one has \(\log (1+t) \leq t\).
This follows from the mean value theorem.
For \(t \geq 0\), one has \(t - \frac{t^2}{2} \leq \log (1+t)\).
Use Taylor’s theorem with remainder and the fact that the second derivative of \(\log (1+t)\) is at most \(1\) for \(t \geq 0\).
For \(0 \leq t \leq t_0 {\lt} 1\), one has \(\frac{t}{t_0} \log (1-t_0) \leq \log (1-t)\).
Use concavity of log.
For \(0 {\lt} t \leq 1/2\), one has \(| \frac{1}{\log (1+t)} + \frac{1}{\log (1-t)}| \leq \frac{16\log (4/3)}{3}\).
The expression can be written as \(\frac{|\log (1-t^2)|}{|\log (1-t)| |\log (1+t)|}\). Now use the previous upper and lower bounds, noting that \(t^2 \leq 1/4\). NOTE: this gives the slightly weaker bound of \(16 \log (4/3) / 3\), but this can suffice for applications. The sharp bound would require showing that the left-hand side is monotone in \(t\), which looks true but not so easy to verify.
\(\operatorname {li}(x) - \operatorname {Li}(x) = \operatorname {li}(2)\).
This follows from the previous estimate.
\(\operatorname {li}(2) = 1.0451\dots \).
Symmetrize the integral and use and some numerical integration.
\(1.039 \leq \operatorname {li}(2) \leq 1.06\).
\(\int _0^1 \left(\frac{1}{\log (1+t)} + \frac{1}{\log (1-t)}\right) dt = \mathrm{li}(2)\)
\(\theta (x) = \sum _{p \leq x} \log p\) where the sum is over primes \(p\).
\(E_\pi (x) = |\pi (x) - \mathrm{Li}(x)| / \mathrm{Li}(x)\)
\(E_\theta (x) = |\theta (x) - x| / x\)
We say that \(E_\theta \) satisfies a classical bound with parameters \(A, B, C, R, x_0\) if for all \(x \geq x_0\) we have
We say that it obeys a numerical bound with parameter \(ε(x_0)\) if for all \(x \geq x_0\) we have
We say that \(E_\pi \) satisfies a classical bound with parameters \(A, B, C, R, x_0\) if for all \(x \geq x_0\) we have
We say that it obeys a numerical bound with parameter \(ε(x_0)\) if for all \(x \geq x_0\) we have
9.2 Chebyshev’s estimates
We record Chebyshev’s estimates on \(\psi \). The material here is adapted from the presentation of Diamond [ 9 ] .
\(T(x) := \sum _{n \leq x} \log n\).
For \(x \geq 1\), we have \(T(x) \leq x \log x - x + 1 + \log x\).
Upper bound \(\log n\) by \(\int _n^{n+1} \log t\ dt\) for \(n {\lt} x-1\) and by \(\log x\) for \(x-1 {\lt} n \leq x\) to bound
giving the claim.
For \(x \geq 1\), we have \(T(x) \leq x \log x - x + 1 - \log x\).
Drop the \(n=1\) term. Lower bound \(\log n\) by \(\int _{n-1}^{n} \log t\ dt\) for \(2 \leq n {\lt} x\) to bound
giving the claim.
For \(x \geq 0\), we have \(T(x) = \sum _{n \leq x} \Lambda (n) \lfloor x/n \rfloor \).
This follows from the identity \(\log n = \sum _{d|n} \Lambda (d)\) and rearranging sums.
If \(\nu : \mathbb {N}\to \mathbb {R}\), let \(E: \mathbb {R}\to \mathbb {R}\) denote the function \(E(x):= \sum _m \nu (m) \lfloor x / m \rfloor \).
If \(\nu : \mathbb {N}\to \mathbb {R}\) is finitely supported, then
\(\nu = e_1 - e_2 - e_3 - e_5 + e_{30}\), where \(e_n\) is the Kronecker delta at \(n\).
One has \(\sum _n \nu (n)/n = 0\)
This follows from direct computation.
One has \(E(x)=1\) for \(1 \leq x {\lt} 6\).
This follows from direct computation.
One has \(E(x+30) = E(x)\).
This follows from direct computation.
One has \(0 \leq E(x) \leq 1\) for all \(x \geq 0\).
This follows from direct computation for \(0 \leq x {\lt} 30\), and then by periodicity for larger \(x\).
We define \(U(x) := \sum _m \nu (m) T(x/m)\).
For any \(x {\gt} 0\), one has \(\psi (x) \geq U(x)\).
For any \(x {\gt} 0\), one has \(\psi (x) - \psi (x/6) \leq U(x)\).
We define \(a := -\sum _m \nu (m) \log m / m\).
We have \(0.92129 \leq a \leq 0.92130\).
For \(x \geq 30\), we have \(|U(x) - ax| \leq 5\log x - 5\).
For \(x \geq 30\), we have \(\psi (x) \geq ax - 5\log x - 1\).
For \(x \geq 30\), we have \(\psi (x) - \psi (x/6) \leq ax + 5\log x - 5\).
Use Lemma 9.2.10 and Proposition ??.
For \(0 {\lt} x \leq 30\), we have \(\psi (x) \leq 1.015 x\).
Numerical check (the maximum occurs at \(x=19\)). One only needs to check the case when \(x\) is a prime power.
For \(x \geq 30\), we have \(\psi (x) \leq 6ax/5 + (\log (x/5) / \log 6) (5 \log x - 5)\).
For \(0 {\lt} x \leq 11723\), we have \(\psi (x) \leq 1.11 x\).
From Lemma 9.2.1 we can take \(x \geq 30\). If one considers the sequence \(x_1,x_2,\dots \) defined by \(27, 32, 37, 43, 50, 58, 67, 77, 88, 100, 114, 129, 147, 166, 187, 211, 238, 268, 302, 340, 381, 427, 479, 536, 600, 671, 750, 839, 938, 1048, 1172, 1310, 1464, 1636, 1827, 2041, 2279, 2544, 2839, 3167, 3534, 3943, 4398, 4905, 5471, 6101, 6803, 7586, 8458, 9431, 10515, 11723\) then one should have \(\psi (x_{j+1}-1) \leq 1.11 x_j\) for all \(j\), which suffices.
For \(x {\gt} 0\), we have \(\psi (x) \leq 1.11 x\).
9.3 An inequality of Costa-Pereira
We record here an inequality relating the Chebyshev functions \(\psi (x)\) and \(\theta (x)\) due to Costa Pereira [ 7 ] , namely
For every \(x {\gt} 0\) we have \(\psi (x) = \sum _{k \geqslant 1} \theta (x^{1/k})\).
This follows directly from the definitions of \(\psi \) and \(\theta \).
For every \(x {\gt} 0\) and \(n\) we have \(\psi (x^{1/n}) = \sum _{k \geqslant 1} \theta (x^{1/nk})\).
Follows from Sublemma 9.3.1 and substitution.
For every \(x {\gt} 0\) we have
For every \(x {\gt} 0\) we have
Follows from Sublemma 9.3.3 and rearranging the sum.
For every \(x {\gt} 0\) we have
Follows from Sublemma 9.3.2 and substitution.
For every \(x {\gt} 0\) we have
For every \(x {\gt} 0\) we have
Follows from Sublemma 9.3.6 and the fact that \(\theta \) is an increasing function.
For every \(x {\gt} 0\) we have
Follows from Sublemma 9.3.6 and the fact that \(\theta \) is an increasing function.
For every \(x {\gt} 0\) we have \(\psi (x) - \theta (x) \leqslant \psi (x^{1/2}) + \psi (x^{1/3}) + \psi (x^{1/5})\).
For every \(x {\gt} 0\) we have \(\psi (x) - \theta (x) \geqslant \psi (x^{1/2}) + \psi (x^{1/3}) + \psi (x^{1/7})\).
9.4 The prime number bounds of Rosser and Schoenfeld
In this section we formalize the prime number bounds of Rosser and Schoenfeld [ 20 ] .
TODO: Add more results and proofs here, and reorganize the blueprint
\(\vartheta (x) = x + O( x / \log ^2 x)\).
This in principle follows by establishing an analogue of Theorem 5.0.1, using mediumPNT in place of weakPNT.
The function \(\vartheta (x) = \sum _{p \leq x} \log p\) defines a Stieltjes function (monotone and right continuous).
Trivial
\(\sum _{p \leq x} f(p) = \int _{2}^x \frac{f(y)}{\log y}\ d\vartheta (y)\).
This follows from the definition of the Stieltjes integral.
\(\sum _{p \leq x} f(p) = \frac{f(x) \vartheta (x)}{\log x} - \int _2^x \vartheta (y) \frac{d}{dy}( \frac{f(y)}{\log y} )\ dy.\)
Follows from Sublemma 9.4.2 and integration by parts.
Follows from Sublemma 9.4.3 and integration by parts.
Follows from Sublemma 9.4.3 applied to \(f(t) = 1\).
Follows from Sublemma 9.4.3 applied to \(f(t) = 1/t\).
\(B := \lim _{x \to \infty } \left( \sum _{p \leq x} \frac{1}{p} - \log \log x \right)\).
Follows from Sublemma 9.4.3 applied to \(f(t) = 1/t\). One can also use this identity to demonstrate convergence of the limit defining \(B\).
\(E := \lim _{x \to \infty } \left( \sum _{p \leq x} \frac{\log p}{p} - \log x \right)\).
We have \(\psi (x) {\lt} c_0 x\) for all \(x{\gt}0\).
9.5 The estimates of Buthe
In this section we collect some results from Buthe’s paper [ 4 ] , which provides explicit estimates on \(\psi (x)\), \(\theta (x)\), and \(\pi (x)\).
TODO: Add more results and proofs here, and reorganize the blueprint
\(\pi ^*(x) = \sum _{k \geq 1} \pi (x^{1/k}) / k\).
If \(11 {\lt} x \leq 10^{19}\), then \(|x - \psi (x)| \leq 0.94\sqrt{x}\).
If \(1423 \leq x \leq 10^{19}\), then \(x - \vartheta (x) \leq 1.95\sqrt{x}\).
If \(1 \leq x \leq 10^{19}\), then \(x - \vartheta (x) {\gt} 0.05\sqrt{x}\).
If \(2 \leq x \leq 10^{19}\), then \(|\operatorname {li}(x) - \pi ^*(x)| {\lt} \frac{\sqrt{x}}{\log x}\).
If \(2 \leq x \leq 10^{19}\), then
If \(2 \leq x \leq 10^{19}\), then \(\mathrm{li}(x) - \pi (x) {\gt} 0\).
9.6 Numerical content of BKLNW
Purely numerical calculations from [ 2 ] . This is kept in a separate file from the main file to avoid heavy recompilations. Because of this, this file should not import any other files from the PNT+ project, other than further numerical data files.
The entries in Table 14 obey the criterion in Sublemma 9.7.2.
9.7 Tools from BKLNW
In this file we record the results from [ 2 ] , excluding Appendix A which is treated elsewhere. These results convert an initial estimate on \(E_\psi (x)\) (provided by Appendix A) to estimates on \(E_\theta (x)\). One first obtains estimates on \(E_\theta (x)\) that do not decay in \(x\), and then obtain further estimates that decay like \(1/\log ^k x\) for some \(k=1,\dots 5\).
9.7.1 Bounding Etheta uniformly
We first focus on getting bounds on \(E_\theta (x)\) that do not decay in \(x\). A key input, provided by Appendix A, is a bound on \(E_\psi (x)\) of the form
We also assume a numerical verification \(\theta (x) {\lt} x\) for \(x \leq x_1\) for some \(x_1 \geq e^7\).
\(\theta (x) {\lt} x\) for all \(1 \leq x \leq 10^{19}\).
This follows from Theorem 9.5.3.
We take \(\varepsilon \) as in Table 8 of [ 2 ] , and \(x_1 = 10^{19}\).
With the hypotheses as above, we have \(\theta (x) \leq (1+\varepsilon (\log x_1)) x)\) for all \(x {\gt} 0\).
Follows immediately from the given hypothesis \(\theta (x) \leq \psi (x)\), splitting into the cases \(x ≥ x_1\) and \(x {\lt} x_1\).
With the hypotheses as above, we have
for all \(x \geq e^b\) and \(b{\gt}0\), where \(c_0 = 1.03883\) is the constant from [ 20 , Theorem 12 ] .
For any fixed \(X_0 \geq 1\), there exists \(m_0 {\gt} 0\) such that, for all \(x \geq X_0\)
For any fixed \(X_1 \geq 1\), there exists \(M_0 {\gt} 0\) such that, for all \(x \geq X_1\)
For \(X_0, X_1 \geq e^{20}\), we have
and
One has \(x(1-m) \leq \theta (x) \leq x(1+M)\) whenever \(x \geq e^b\) and \(b,M,m\) obey the condition that \(b \geq 20\), \(\varepsilon (b) \leq M\), and \(\varepsilon (b) + c_0 (e^{-b/2} + e^{-2b/3} + e^{-4b/5}) \leq m\).
The previous theorem holds with \((b,M,m)\) given by the values in [ 2 , Table 14 ] .
\(\theta (x) \leq (1 + 1.93378 \times 10^{-8}) x\).
We take \(\alpha = 1.93378 \times 10^{-8}\), so that we have \(\theta (x) \leq (1 + \alpha ) x\) for all \(x\).
9.7.2 Bounding psi minus theta
In this section we obtain bounds of the shape
for all \(x \geq x_0\) and various \(a_1, a_2, x_0\).
Let \(x \geq x_0\) and let \(\alpha \) be admissible. Then
Bound each \(\theta (x^{1/k})\) term by \((1 + \alpha )x^{1/k}\) in Sublemma 9.3.1.
\(f\) decreases on \([2^n, 2^{n+1})\).
Clear.
\(f(2^n) = 1 + u_n\).
Clear.
\(u_{n+1} {\lt} u_n\) for \(n \geq 9\).
We have
Define \(s(k, n) := 2^{\frac{n+1}{k}}(2^{\frac{1}{3} - \frac{1}{k}} - 1)\). Note that \(s(k, n)\) is monotone increasing in \(n\) for each fixed \(k \geq 4\). By numerical computation (using the trick \(x \le 2 ^{p / q} \iff x ^q \le 2 ^p\) to verify decimal lower bounds \(x\)), \(\sum _{k=4}^{n} s(k, n) \ge \sum _{k=4}^{9} s(k, 9) {\gt} 2.12 {\gt} 2\). Thus \(u_{n+1} - u_n {\lt} 0\).
\(f(2^n) {\gt} f(2^{n+1})\) for \(n \geq 9\).
\(f(x) \leq f(2^{\lfloor \frac{\log x_0}{\log 2} \rfloor + 1})\) on \([2^{\lfloor \frac{\log x_0}{\log 2} \rfloor + 1}, \infty )\).
\(f(x) \leq f(x_0)\) for \(x \in [x_0, 2^{\lfloor \frac{\log x_0}{\log 2} \rfloor + 1})\).
Follows since \(f(x)\) decreases on \([2^{\lfloor \frac{\log x_0}{\log 2} \rfloor }, 2^{\lfloor \frac{\log x_0}{\log 2} \rfloor + 1})\).
\(f(x) \leq \max \left(f(x_0), f(2^{\lfloor \frac{\log x_0}{\log 2} \rfloor + 1})\right)\).
Combines previous sublemmas.
Let \(x_0 \geq 2^9\). Let \(\alpha {\gt} 0\) exist such that \(\theta (x) \leq (1 + \alpha )x\) for \(x {\gt} 0\). Then for \(x \geq x_0\),
where
with
Combines previous sublemmas.
Let \(b \geq 7\). Assume \(x \geq e^b\). Then we have
where
We apply Proposition 9.7.1 with \(x_0 = e^b\) where we observe that \(x_0 = e^b \geq e^7 {\gt} 2^9\).
If \(7 \leq b \leq 2\log x_1\), then we have
Note that in the paper, the inequality in Proposition 4 is strict, but the argument can only show nonstrict inequalities. If \(e^b \leq x \leq x_1^2\), then \(x^{1/2} \leq x_1\), and thus
On the other hand, if \(x^{1/2} {\gt} x_1 = e^{\log x_1}\), then we have by (2.7)
since \(\log x_1 \geq 7\). The last two inequalities for \(\theta (x^{1/2})\) combine to establish (2.8).
If \(b {\gt} 2\log x_1\), then we have
Note that in the paper, the inequality in Proposition 4 is strict, but the argument can only show nonstrict inequalities. As in the above subcase, we have for \(x \geq e^b\)
since \(x^{1/2} {\gt} e^{b/2} {\gt} x_1 \geq e^7\).
\(a_1\) is equal to \(1 + \varepsilon (\log x_1)\) if \(b \leq 2\log x_1\), and equal to \(1 + \varepsilon (b/2)\) if \(b {\gt} 2\log x_1\).
\(a_2\) is defined by
Let \(\alpha {\gt} 0\) exist such that
Assume for every \(b \geq 7\) there exists a positive constant \(\varepsilon (b)\) such that
Assume there exists \(x_1 \geq e^7\) such that
Let \(b \geq 7\). Then, for all \(x \geq e^b\) we have
where
and
We have \(\psi (x) - \theta (x) = \theta (x^{1/2}) + \sum _{k=3}^{\lfloor \frac{\log x}{\log 2} \rfloor } \theta (x^{1/k})\). For any \(b \geq 7\), setting \(x_0 = e^b\) in Proposition 4, we bound \(\sum _{k=3}^{\lfloor \frac{\log x}{\log 2} \rfloor } \theta (x^{1/k})\) by \(\eta x^{1/3}\) as defined in (2.3). We bound \(\theta (x^{1/2})\) with Proposition ?? by taking either \(a_1 = 1 + \varepsilon (\log x_1)\) for \(b \leq 2\log x_1\) or \(a_1 = 1 + \varepsilon (b/2)\) for \(b {\gt} 2\log x_1\).
Let \(b \geq 7\). Then for all \(x \geq e^b\) we have \(\psi (x) - \vartheta (x) {\lt} a_1 x^{1/2} + a_2 x^{1/3}\), where \(a_1 = a_1(b) = 1 + 1.93378 \times 10^{-8}\) if \(b \leq 38 \log 10\), \(1 + \varepsilon (b/2)\) if \(b {\gt} 38 \log 10\), and \(a_2 = a_2(b) = (1 + 1.93378 \times 10^{-8}) \max \left( f(e^b), f(2^{\lfloor \frac{b}{\log 2} \rfloor + 1}) \right)\), where \(f\) is defined by (2.4) and values for \(\varepsilon (b/2)\) are from Table 8.
This is Theorem 5 applied to the default inputs in Definition 9.7.2.
We have the following values for \(a_2\), given by the table after [ 2 , Corollary 5.1 ] .
9.7.3 Bounding theta(x)-x with a logarithmic decay, I: large x
In this section and the next ones we obtain bounds of the shape
for all \(x \geq X_0\) and
for all \(x \geq X_1\), for various \(k, m_k, M_k, X_0, X_1\), with \(k \in \{ 1,\dots ,5\} \).
For this section we focus on estimates that are useful when \(x\) is extremely large, e.g., \(x \geq e^{25000}\).
Suppose there exists \(c_1, c_2, c_3, c_4 {\gt} 0\) such that
Let \(k {\gt} 0\) and let \(b \geq \max \left(\log c_4, \log \left(\frac{4(c_2 + k)^2}{c_3^2}\right)\right)\). Then for all \(x \geq e^b\) we have
where
We denote \(g(x) = (\log x)^{c_2 + k} \exp (-c_3 (\log x)^{\frac{1}{2}})\). By ??, \(|\theta (x) - x| {\lt} \frac{c_1 g(x) x}{(\log x)^k}\) for all \(x \geq c_4\). It suffices to bound \(g\): by calculus, \(g(x)\) decreases when \(x \geq \frac{4(c_2 + k)^2}{c_3^2}\). Therefore \(|\theta (x) - x| \leq \frac{c_1 g(e^b) x}{(\log x)^k}\). Note that \(c_1 g(e^b) = \mathcal{A}_k(b)\) and the condition on \(b\) follows from the conditions \(e^b \geq c_4\) and \(e^b \geq \frac{4(c_2 + k)^2}{c_3^2}\).
Suppose one has an asymptotic bound \(E_\psi \) with parameters \(A,B,C,R,e^{x_0}\) (which need to satisfy some additional bounds) with \(x_0 \geq 1000\). Then \(E_\theta \) obeys an asymptotic bound with parameters \(A', B, C, R, e^{x_0}\), where
and \(a_1(x_0), a_2(x_0)\) are as in Corollary 9.7.3.
We write \(\theta (x) - x = \psi (x) - x + \theta (x) - \psi (x)\), apply the triangle inequality, and invoke Corollary ?? to obtain
The function in brackets decreases for \(x \geq e^{x_0}\) with \(x_0 \geq 1000\) (assuming reasonable hypotheses on \(A,B,C,R\)) and thus we obtain the desired bound with \(A'\) as above.
9.7.4 Bounding theta(x)-x with a logarithmic decay, II: medium x
In this section we tackle medium \(x\).
TODO: formalize Lemma 8 and Corollary 8.1
9.7.5 Bounding theta(x)-x with a logarithmic decay, III: small x
In this section we tackle small \(x\).
TODO: formalize (3.17), (3.18), Lemma 9, Corollary 9.1
9.7.6 Bounding theta(x)-x with a logarithmic decay, IV: very small x
In this section we tackle very small \(x\).
TODO: Formalize Lemma 10
9.7.7 Final bound on Etheta(x)
Now we put everything together.
TODO: Section 3.7.1; 3.7.2; 3.7.3; 3.7.4
Let \(k\) be an integer with \(1 \leq k \leq 5\). For any fixed \(X_0 {\gt} 1\), there exists \(m_k {\gt} 0\) such that, for all \(x \geq X_0\)
For any fixed \(X_1 {\gt} 1\), there exists \(M_k {\gt} 0\) such that, for all \(x \geq X_1\)
In the case \(k = 0\) and \(X_0, X_1 \geq e^{20}\), we have
and
See [ 2 , Table 15 ] for values of \(m_k\) and \(M_k\), for \(k \in \{ 1,2,3,4,5\} \).
9.7.8 Computational examples
Now we apply the previous theorem.
TODO: Corollary 11.1, 11.2
9.8 The implications of FKS2
In this file we record the implications in the paper [ 14 ] . Roughly speaking, this paper has two components: a "\(\psi \) to \(\theta \) pipeline" that converts estimates on the error \(E_\psi (x) = |\psi (x)-x|/x\) in the prime number theorem for the first Chebyshev function \(\psi \) to estimates on the error \(E_\theta (x) = |\theta (x)-x|/x\) in the prime number theorem for the second Chebyshev function \(\theta \); and a "\(\theta \) to \(\pi \) pipeline" that converts estimates \(E_\theta \) to estimates on the error \(E_\pi (x) = |\pi (x) - \operatorname {Li}(x)|/(x/\log x)\) in the prime number theorem for the prime counting function \(\pi \). Each pipeline converts "admissible classical bounds" (Definitions 8.1.2 9.1.6, 9.1.7) of one error to admissible classical bounds of the next error in the pipeline.
There are two types of bounds considered here. The first are asymptotic bounds of the form
for various \(A,B,C,R\) and all \(x \geq x_0\). The second are numerical bounds of the form
for all \(x \geq x_0\) and certain specific numerical choices of \(x_0\) and \(\varepsilon _{num}(x_0)\). One needs to merge these bounds together to obtain the best final results.
9.8.1 Basic estimates on the error bound g
Our asymptotic bounds can be described using a certain function \(g\). Here we define \(g\) and record its basic properties.
For any \(a,b,c,x \in \mathbb {R}\) we define \(g(a,b,c,x) := x^{-a} (\log x)^b \exp ( c (\log x)^{1/2} )\).
We have
This follows from straightforward differentiation.
\(\frac{d}{dx} g(a, b, c, x) \) is negative when \(-au^2 + \frac{c}{2}u + b {\lt} 0\), where \(u = \sqrt{\log (x)}\).
Clear from previous sublemma.
If \(a{\gt}0\), \(c{\gt}0\) and \(b {\lt} -c^2/16a\), then \(g(a,b,c,x)\) decreases with \(x\).
We apply Lemma 9.8.2. There are no roots when \(b {\lt} -\frac{c^2}{16a}\), and the derivative is always negative in this case.
For any \(a{\gt}0\), \(c{\gt}0\) and \(b \geq -c^2/16a\), \(g(a,b,c,x)\) decreases with \(x\) for \(x {\gt} \exp ((\frac{c}{4a} + \frac{1}{2a} \sqrt{\frac{c^2}{4} + 4ab})^2)\).
We apply Lemma 9.8.2. If \(a {\gt} 0\), there are two real roots only if \(\frac{c^2}{4} + 4ab \geq 0\) or equivalently \(b \geq -\frac{c^2}{16a}\), and the derivative is negative for \(u {\gt} \frac{\frac{c}{2} + \sqrt{\frac{c^2}{4} + 4ab}}{2a}\).
If \(c{\gt}0\), \(g(0,b,c,x)\) decreases with \(x\) for \(\sqrt{\log x} {\lt} -2b/c\).
If \(B \geq 1 + C^2 / 16R\) then \(g(1,1-B,C/\sqrt{R},x)\) is decreasing in \(x\).
This follows from Lemma 9.8.1 applied with \(a=1\), \(b=1-B\) and \(c=C/\sqrt{R}\).
When integrating expressions involving \(g\), the Dawson function naturally appears; and we need to record some basic properties about it.
The Dawson function \(D_+ : \mathbb {R} \to \mathbb {R}\) is defined by the formula \(D_+(x) := e^{-x^2} \int _0^x e^{t^2}\ dt\).
The Dawson function has a single maximum at \(x \approx 0.942\), after which the function is decreasing.
The Dawson function satisfies the differential equation \(F'(x) + 2xF(x) = 1\) from which it follows that the second derivative satisfies \(F''(x) = −2F(x) − 2x(−2xF(x) + 1)\), so that at every critical point (where we have \(F(x) = \frac{1}{2x}\)) we have \(F''(x) = −\frac{1}{x}\). It follows that every positive critical value gives a local maximum, hence there is a unique such critical value and the function decreases after it. Numerically one may verify this is near 0.9241 see https://oeis.org/ A133841.
9.8.2 From asymptotic estimates on psi to asymptotic estimates on theta
To get from asymptotic estimates on \(E_\psi \) to asymptotic estimates on \(E_\theta \), the paper cites results and arguments from the previous paper [ 2 ] , which is treated elsewhere in this blueprint.
Suppose that \(A_\psi ,B,C,R,x_0\) give an admissible bound for \(E_\psi \). If \(B {\gt} C^2/8R\), then \(A_\theta , B, C, R, x_0\) give an admissible bound for \(E_\theta \), where
with
The proof of Corollary 9.7.4 essentially proves the proposition, but requires that \(x_0 \geq e^{1000}\) to conclude that the function
is decreasing. By Lemma 9.8.1, since \(B {\gt} C^2/8R\), the function is actually decreasing for all \(x\).
We have an admissible bound for \(E_\theta \) with \(A = 121.0961\), \(B=3/2\), \(C=2\), \(R = 5.5666305\), \(x_0=2\).
By Corollary 8.3.23, with \(R = 5.5666305\), and using the admissible asymptotic bound for \(E_\psi (x)\) with \(A_\psi = 121.096\), \(B = 3/2\), \(C = 2\), for all \(x \geq x_0 = e^{30}\), we can obtain \(\nu _{asymp}(x_0) \leq 6.3376 \cdot 10^{-7}\), from which one can conclude an admissible asymptotic bound for \(E_\theta (x)\) with \(A_\theta = 121.0961\), \(B = 3/2\), \(C = 2\), for all \(x \geq x_0 = e^{30}\). Additionally, the minimum value of \(\varepsilon _{\theta ,asymp}(x)\) for \(2 \leq x \leq e^{30}\) is roughly \(2.6271\ldots \) at \(x=2\). The results found in [ 2 , Table 13 and 14 ] give \(E_\theta (x) \leq 1 {\lt} \varepsilon _{\theta ,asymp}(2) \leq \varepsilon _{\theta ,asymp}(x)\) for all \(2 \leq x \leq e^{30}\).
If \(\log x_0 \geq 1000\) then we have an admissible bound for \(E_\theta \) with the indicated choice of \(A(x_0)\), \(B = 3/2\), \(C = 2\), and \(R = 5.5666305\).
From [ 13 , Table 6 ] we have \(\nu _{asymp}(x_0) \leq 10^{-200}\). Thus, one easily verifies that the rounding up involved in forming [ 13 , Table 6 ] exceeds the rounding up also needed to apply this step. Consequently we may use values from \(A_\theta \) taken from [ 13 , Table 6 ] directly but this does, in contrast to Corollary 9.8.2, require the assumption \(x {\gt} x_0\), as per that table.
9.8.3 From asymptotic estimates on theta to asymptotic estimates on pi
To get from asymptotic estimates on \(E_\theta \) to asymptotic estimates on \(E_\pi \), one first needs a way to express the latter as an integral of the former.
For any \(2 \leq x_0 {\lt} x\) one has
This follows from Sublemma 9.4.6.
The following definition is only implicitly in FKS2, but will be convenient:
For any \(x_0{\gt}0\), we define
We can now obtain an upper bound on \(E_\pi \) in terms of \(E_\theta \):
For any \(x \geq x_0 {\gt} 0\),
This follows from applying the triangle inequality to Sublemma 9.8.3.
Next, we bound the integral appearing in Sublemma 9.8.3.
Suppose that \(E_\theta \) satisfies an admissible classical bound with parameters \(A,B,C,R,x_0\). Then, for all \(x \geq x_0\),
where
Since \(\varepsilon _{\theta ,\mathrm{asymp}}(t)\) provides an admissible bound on \(\theta (t)\) for all \(t \geq x_0\), we have
We perform the substitution \(u = \sqrt{\log (t)}\) and note that \(u^{2B-3} \leq m(x_0, x)\) as defined in (21). Thus the above is bounded above by
Then, by completing the square \(u^2 - \frac{Cu}{\sqrt{R}} = \left( u - \frac{C}{2\sqrt{R}} \right)^2 - \frac{C^2}{4R}\) and doing the substitution \(v = u - \frac{C}{2\sqrt{R}}\), the above becomes
Now we have
Combining the above completes the proof.
For \(x_0,x_1 {\gt} 0\), we define
.
We obtain our final bound for converting bounds on \(E_\theta \) to bounds on \(E_\pi \).
If \(B \geq \max (3/2, 1 + C^2/16 R)\), \(x_0 {\gt} 0\), and one has an admissible asymptotic bound with parameters \(A,B,C,x_0\) for \(E_\theta \), and
then
for all \(x \geq x_1\). In other words, we have an admissible bound with parameters \((1+\mu _{asymp}(x_0,x_1))A, B, C, x_1\) for \(E_\pi \).
The starting point is Sublemma 9.8.4. The assumption (\(\varepsilon _{\theta ,\mathrm{asymp}}(x)\) provides an admissible bound on \(\theta (x)\) for all \(x \geq x_0\)) to bound \(\frac{\theta (x) - x}{\log (x)}\) and Lemma 9.8.4 to bound \(\int _{x_0}^{x} \frac{\theta (t) - t}{t (\log (t))^2} dt\). We obtain
We recall that \(x \geq x_1 \geq x_0\). Note that, by Corollary 9.8.1,
is decreasing for all \(x\). Thus,
In addition, we have the simplification
by Definition 9.1.6 and by \(m(x_0,x) = (\log (x))^{(2B - 3)/2}\), since \(B \geq 3/2\). Finally, since \(\sqrt{\log (x_1)} - \frac{C}{2\sqrt{R}} {\gt} 1\), the Dawson function decreases for all \(x \geq x_1\):
We conclude by combining the above:
from which we deduce the announced bound.
9.8.4 From numerical estimates on psi to numerical estimates on theta
Here we record a way to convert a numerical bound on \(E_\psi \) to a numerical bound on \(E_\theta \).
Let \(x {\gt} x_0 {\gt} 2\). If \(E_\psi (x) \leq \varepsilon _{\psi ,num}(x_0)\), then
where
The upper bound is immediate since \(\theta (x) \leq \psi (x)\) for all \(x\). For the lower bound, we have
By Theorem 9.3.1, we have
We use [ 4 , Theorem 2 ] , that for \(0 {\lt} x {\lt} 11\), \(\psi (x) {\lt} x\), and that \(\varepsilon _{\psi ,num}(10^{19}) {\lt} 2 \cdot 10^{-8}\). In particular when \(2 {\lt} x {\lt} 10^{38}\),
when \(10^{38} \leq x {\lt} 10^{54}\),
when \(10^{54} \leq x {\lt} 10^{95}\),
and finally when \(x \geq 10^{95}\),
The result follows by combining the worst coefficients from all cases and dividing by \(x\).
9.8.5 From numerical estimates on theta to numerical estimates on pi
Here we record a way to convert a numerical bound on \(E_\theta \) to a numerical bound on \(E_\pi \). We first need some preliminary lemmas.
Let \(x_1 {\gt} x_0 \geq 2\), \(N \in \mathbb {N}\), and let \((b_i)_{i=1}^N\) be a finite partition of \([x_0,x_1]\). Then
We split the integral at each \(e^{b_i}\) and apply the bound
Thus,
We conclude by using the identity: for all \(2 \leq a {\lt} b\),
The function \(\operatorname {Li}(x) - \frac{x}{\log x}\) is strictly increasing for \(x {\gt} 6.58\).
Differentiate
to see that the difference is strictly increasing. Evaluating at \(x = 6.58\) and applying the mean value theorem gives the announced result.
Assume \(x {\gt} 6.58\). Then \(\operatorname {Li}(x) - \frac{x}{\log x} {\gt} \frac{x-6.58}{\log ^2 x} {\gt} 0\).
This follows from Lemma 9.8.6 and the mean value theorem.
Now we can start estimating \(E_\pi \). We make the following running hypotheses. Let \(x_0 {\gt} 0\) be chosen such that \(\pi (x_0)\) and \(\theta (x_0)\) are computable, and let \(x_1 \geq \max (x_0, 14)\). Let \(\{ b_i\} _{i=1}^N\) be a finite partition of \([\log x_0, \log x_1]\), with \(b_1 = \log x_0\) and \(b_N = \log x_1\), and suppose that \(\varepsilon _{\theta ,\mathrm{num}}\) gives numerical bounds for \(x = \exp (b_i)\), for each \(i=1,\dots ,N\).
With the above hypotheses, for all \(x \geq x_1\) we have
This is obtained by combining Sublemma ?? with the admissibility of \(\varepsilon _{\theta ,num}\) and Lemma 9.8.5.
With the above hypotheses, for all \(x \geq x_1\) we have
Call the left-hand side \(f(x)\). We have
Using integration by parts, its derivative can be written as
From which we see that \(f'(x_1) = \frac{1}{\log x_1} {\gt} 0\), and that \(f'(x)\) is eventually negative. Thus there exists a critical point for \(f(x)\) to the right of \(x_1\). Moreover, by bounding \(\int _{x_1}^x \frac{6}{\log ^4 t} dt {\lt} 6 \frac{x - x_1}{\log ^4 x_1}\), one finds that \(f'(x_1 \log x_1) {\gt} 0\) if \(x_1 {\gt} e\). Now we write \(f'(x) = \frac{f_1(x)}{x^2}\) with
Its derivative is \(f_1'(x) = -\frac{1}{x} \int _{x_1}^x \frac{1}{\log ^2 t} dt\), which is negative for \(x {\gt} x_1\). Thus \(f_1(x)\) decreases and vanishes at most once, giving \(f(x)\) at most one critical point, \(x_m {\gt} x_1\), which is then the maximum of \(f(x)\). In other words, \(x_m\) satisfies \(f_1(x_m) = 0\), i.e. \(\mathrm{Li}(x_m) - \mathrm{Li}(x_1) + \frac{x_1}{\log x_1} = -\frac{x_m}{1 - \log x_m}\), which shows that \(f(x)\) attains its maximum at \(x = x_m\), where
Now, because \(x_m {\gt} x_1 \log x_1\) we obtain the bound
which gives the announced result.
With the above hypotheses, for all \(x \geq x_1\) we have
Let \(f(x)\) be as in the previous sublemma. Notice that by assumption \(x_1 \leq x \leq x_2 \leq x_1 \log x_1 {\lt} x_m\), so that
We can merge these sublemmas together after making some definitions.
For \(x_1 \leq x_2 \leq x_1 \log x_1\), we define
For \(x_2 \geq x_1 \log x_1\), we define
We define \(\mu _{num}(x_0, x_1, x_2)\) to equal \(\mu _{num,1}(x_0,x_1,x_2)\) when \(x_2 \leq x_1 \log x_1\) and \(\mu _{num,2}(x_0,x_1)\) otherwise.
For \(x_1 \leq x_2\), we define \(\epsilon _{\pi ,num}(x_0,x_1,x_2) := \epsilon _{\theta ,num}(x_1) (1 + \mu _{num}(x_0,x_1,x_2))\).
If
then \(\mu _{num,1}(x_0,x_1,x_2) {\lt} \mu _{num,2}(x_0,x_1)\).
This follows from the definitions of \(\mu _{num,1}\) and \(\mu _{num,2}\).
This gives us the final result to obtain numerical bounds for \(E_\pi \) from numerical bounds on \(E_\theta \).
Let \(x_0 {\gt} 0\) be chosen such that \(\pi (x_0)\) and \(\theta (x_0)\) are computable, and let \(x_1 \geq \max (x_0, 14)\). Let \(\{ b_i\} _{i=1}^N\) be a finite partition of \([\log x_0, \log x_1]\), with \(b_1 = \log x_0\) and \(b_N = \log x_1\), and suppose that \(\varepsilon _{\theta ,\mathrm{num}}\) gives computable admissible numerical bounds for \(x = \exp (b_i)\), for each \(i=1,\dots ,N\). For \(x_1 \leq x_2 \leq x_1 \log x_1\), we define
and for \(x_2 {\gt} x_1 \log x_1\), including the case \(x_2 = \infty \), we define
Then, for all \(x_1 \leq x \leq x_2\) we have
This follows by combining the three substeps.
Let \(\{ b'_i\} _{i=1}^M\) be a set of finite subdivisions of \([\log (x_1),\infty )\), with \(b'_1 = \log (x_1)\) and \(b'_M = \infty \). Define
Then \(E_\pi (x) \leq \varepsilon _{\pi ,num}(x_1)\) for all \(x \geq x_1\).
This follows directly from Theorem 9.8.2 by taking the supremum over all partitions ending at infinity.
9.8.6 Putting everything together
By merging together the above tools with various parameter choices, we can obtain some clean corollaries.
Let \(B \geq \max (\frac{3}{2}, 1 + \frac{C^2}{16R})\) and \(B {\gt} C^2/8R\). Let \(x_0, x_1 {\gt} 0\) with \(x_1 \geq \max (x_0, \exp ( (1 + \frac{C}{2\sqrt{R}})^2))\). If \(E_\psi \) satisfies an admissible classical bound with parameters \(A_\psi ,B,C,R,x_0\), then \(E_\pi \) satisfies an admissible classical bound with \(A_\pi , B, C, R, x_1\), where
for all \(x \geq x_0\), where
where
and
One has
for all \(x \geq 2\).
We fix \(R = 1\), \(x_0 = 2\), \(x_1 = e^{100}\), \(A_\theta = 9.2211\), \(B = 1.5\) and \(C = 0.8476\). By Corollary 9.8.2, these are admissible for all \(x \geq 2\), so we can apply Theorem 9.8.1 and calculate that
This implies that \(A_\pi = 121.103\) is admissible for all \(x \geq e^{20000}\).
As in the proof of [ 13 , Lemmas 5.2 and 5.3 ] one may verify that the numerical results obtainable from Theorem 9.8.2, using Corollary 9.8.3, may be interpolated as a step function to give a bound on \(E_\pi (x)\) of the shape \(\varepsilon _{\pi ,asymp}(x)\). In this way we obtain that \(A_\pi = 121.107\) is admissible for \(x {\gt} 2\). Note that the subdivisions we use are essentially the same as used in [ 13 , Lemmas 5.2 and 5.3 ] . In Table 5 we give a sampling of the relevant values, more of the values of \(\varepsilon _{\pi ,num}(x_1)\) can be found in Table 4. Far more detailed versions of these tables will be posted online in https://arxiv.org/src/2206.12557v1/anc/PrimeCountingTables.pdf.
\(A_\pi , B, C, x_0\) as in [ 14 , Table 6 ] give an admissible asymptotic bound for \(E_\pi \) with \(R = 5.5666305\).
The bounds of the form \(\varepsilon _{\pi , asymp}(x)\) come from selecting a value \(A\) for which Corollary ?? provides a better bound at \(x = e^{7500}\) and from verifying that the bound in Corollary ?? decreases faster beyond this point. This final verification proceeds by looking at the derivative of the ratio as in Lemma ??. To verify these still hold for smaller \(x\), we proceed as below. To verify the results for any \(x\) in \(\log (10^{19}) {\lt} \log (x) {\lt} 100000\), one simply proceeds as in [ 13 , Lemmas 5.2, 5.3 ] and interpolates the numerical results of Theorem 9.8.2. For instance, we use the values in Table 4 as a step function and verifies that it provides a tighter bound than we are claiming. Note that our verification uses a more refined collection of values than those provided in Table 4 or the tables posted online in https://arxiv.org/src/2206.12557v1/anc/PrimeCountingTables.pdf. To verify results for \(x {\lt} 10^{19}\), one compares against the results from Theorem 9.5.1, or one checks directly for particularly small \(x\).
We have the bounds \(E_\pi (x) \leq B(x)\), where \(B(x)\) is given by Table 7.
Same as in Corollary ??.
One has
for all \(x \geq 2\).
We numerically verify that the inequality holds by showing that, for \(1 \leq n \leq 25\) and all \(x \in [p_n, p_{n+1}]\),
For \(x\) satisfying \(p_{25} = 97 \leq x \leq 10^{19}\), we use Theorems 9.5.5, 9.5.6 and verify
For \(x {\gt} 10^{19}\), we use Theorem ?? as well as values for \(\varepsilon _{\pi ,num}(x)\) found in Table 4 to conclude
9.9 Dusart’s explicit estimates for primes
In this section we record the estimates of Dusart [ 12 ] on explicit estimates for sums over primes.
TODO: add more results and proofs here, and reorganize the blueprint
For \(x \geq e^{b}\) we have \(\psi (x) - x| \leq \varepsilon \), where \(b, \varepsilon \) are given by [ 12 , Table 1 ] .
We have \(|\psi (x) - x| {\lt} \eta _k x / \log ^k x\) for \(x \geq 2\) with \((k,\eta )\) given by the table in [ 12 , Theorem 3.3 ] .
We have \(\vartheta (x)\) and \(\psi (x)-\vartheta (x)\) for various \(x\) given by [ 12 , Table 2 ] , in particular \(\vartheta (10^{15}) = 999999965752660.939839805291048\dots \)
We have \(|\vartheta (x) - x| {\lt} \eta _k x / \log ^k x\) for \(x \geq x_k\) with \((k,\eta _k,x_k)\) given by the table in [ 12 , Theorem 4.2 ] .
For \(x \geq 121\), we have
For \(x {\gt} 0\), we have
For \(x {\gt} 0\), we have
For \(x \geq 4 \times 10^9\), we have
For \(x \geq 17\), we have
For \(x {\gt} 1\), we have
For \(x \geq 599\), we have
For \(x {\gt} 1\), we have
For \(x \geq 88789\), we have
For \(x {\gt} 1\), we have
For \(x \geq 5393\), we have
For \(x {\gt} e^{1.112}\), we have
For \(x \geq 468049\), we have
For \(x {\gt} 5.6\), we have
There exists a constant \(X_0\) (one may take \(X_0 = 89693\)) with the following property: for every real \(x \geq X_0\), there exists a prime \(p\) with
For all \(x \geq 468991632\), there exists a prime \(p\) such that
We have for \(x \geq 2278383\),
We have for \(x \geq 912560\),
We have for \(x \geq 2278382\),
We have for \(x \geq 2278382\),
We have for \(k \geq 4\), \(p_k \leq k \log p_k\).
We have for \(k \geq 2\), \(\log p_k \leq \log k + \log \log k + 1\).
We have for \(k \geq 198\),
We have for \(p_k \geq 10^{11}\),
We have for \(p_k \geq 10^{15}\),
We have for \(k \geq 781\),
We have for \(k \geq 178974\),
We have for \(k \geq 688383\),
We have for \(k \geq 3\),
9.10 Summary of results
Here we list some papers that we plan to incorporate into this section in the future, and list some results that have not yet been moved into dedicated paper sections.
References to add:
Dusart [ 12 ]
PT: D. J. Platt and T. S. Trudgian, The error term in the prime number theorem, Math. Comp. 90 (2021), no. 328, 871–881.
JY: D. R. Johnston, A. Yang, Some explicit estimates for the error term in the prime number theorem, arXiv:2204.01980.
One has
for all \(x \geq \exp (2000)\).
One has
for all \(x \geq 2\).
One has
for all \(x \geq 2\).
TODO: input other results from JY
The results below are taken from https://tme-emt-wiki-gitlab-io-9d3436.gitlab.io/Art09.html
If \(x {\gt} 2010760\), then there is a prime in the interval
If \(x {\gt} 10,726,905,041\), then there is a prime in the interval \((x(1-1/28314000), x]\).
If \(x {\gt} \exp (53)\), then there is a prime in the interval
If \(x {\gt} \exp (60)\), then there is a prime in the interval
If \(x {\gt} \exp (60)\), then there is a prime in the interval
If \(x {\gt} \exp (60)\), then there is a prime in the interval
If \(x {\gt} 2,898,242\), then there is a prime in the interval
If \(x {\gt} \exp (\exp (34.32))\), then there is a prime in the interval
If \(x {\gt} \exp (\exp (33.99))\), then there is a prime in the interval
Assuming the Riemann Hypothesis, for \(x \geq 2\), there is a prime in the interval
Assuming the Riemann Hypothesis, for \(x \geq 2\), there is a prime in the interval
Assuming the Riemann Hypothesis, for \(x \geq 4\), there is a prime in the interval