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AlexKontorovich committed Jan 25, 2024
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/-%%
\begin{theorem}\label{chebyshev-asymptotic} One has
$$ \sum_{p \leq x} \log p = x + o(x).$$
\end{theorem}
\begin{proof}
\uses{StrongPNT}
From the prime number theorem we already have
$$ \sum_{n \leq x} \Lambda(n) = x + o(x)$$
so it suffices to show that
$$ \sum_{j \geq 2} \sum_{p^j \leq x} \log p = o(x).$$
Only the terms with $j \leq \log x / \log 2$ contribute, and each $j$ contributes at most $\sqrt{x} \log x$ to the sum, so the left-hand side is $O( \sqrt{x} \log^2 x ) = o(x)$ as required.
\end{proof}
\begin{corollary}[Bounds on primorial] We have
\begin{corollary}[Bounds on primorial] \label{primorial-bounds}
We have
$$ \prod_{p \leq x} p = \exp( x + o(x) )$$
\end{corollary}
\begin{proof}
\uses{chebyshev-asymptotic}
Exponentiate Theorem \ref{chebyshev-asymptotic}.
\end{proof}
Expand All @@ -25,7 +29,9 @@
as $x \to \infty$.
\end{theorem}
\begin{proof} We have the identity
\begin{proof}
\uses{chebyshev-asymptotic}
We have the identity
$$ \pi(x) = \frac{1}{\log x} \sum_{p \leq x} \log p
+ \int_2^x (\sum_{p \leq t} \log p) \frac{dt}{t \log^2 t}$$
as can be proven by interchanging the sum and integral and using the fundamental theorem of calculus. For any $\eps$, we know from Theorem \ref{chebyshev-asymptotic} that there is $x_\eps$ such that
Expand All @@ -43,7 +49,9 @@
as $x \to \infty$.
\end{corollary}
\begin{proof} An integration by parts gives
\begin{proof}
\uses{pi-asymp}
An integration by parts gives
$$ \int_2^x \frac{dt}{\log t} = \frac{x}{\log x} - \frac{2}{\log 2} + \int_2^x \frac{dt}{\log^2 t}.$$
We have the crude bounds
$$ \int_2^{\sqrt{x}} \frac{dt}{\log^2 t} = O( \sqrt{x} )$$
Expand All @@ -57,31 +65,41 @@
Let $p_n$ denote the $n^{th}$ prime.
\begin{proposition} One has
\begin{proposition}\label{pn-asymptotic}
One has
$$ p_n = (1+o(1)) n \log n$$
as $n \to \infty$.
\end{proposition}
\begin{proof} Use Corollary \ref{pi-alt} to show that for any $\eps>0$, and for $x$ sufficiently large, the number of primes up to $(1-\eps) n \log n$ is less than $n$, and the number of primes up to $(1+\eps) n \log n$ is greater than $n$.
\begin{proof}
\uses{pi-alt}
Use Corollary \ref{pi-alt} to show that for any $\eps>0$, and for $x$ sufficiently large, the number of primes up to $(1-\eps) n \log n$ is less than $n$, and the number of primes up to $(1+\eps) n \log n$ is greater than $n$.
\end{proof}
\begin{corollary} We have $p_{n+1} - p_n = o(p_n)$
\begin{corollary} \label{pn-pn+1}
We have $p_{n+1} - p_n = o(p_n)$
as $n \to \infty$.
\end{corollary}
\begin{proof} Easy consequence of preceding proposition.
\begin{proof}
\uses{pn-asymptotic}
Easy consequence of preceding proposition.
\end{proof}
\begin{corollary} For every $\eps>0$, there is a prime between $x$ and $(1+\eps x)$ for all sufficiently large $x$.
\begin{corollary} \label{prime-between}
For every $\eps>0$, there is a prime between $x$ and $(1+\eps x)$ for all sufficiently large $x$.
\end{corollary}
\begin{proof} Use Corollary \ref{pi-alt} to show that $\pi((1+\eps)x) - \pi(x)$ goes to infinity as $x \to \infty$.
\begin{proof}
\uses{pi-alt}
Use Corollary \ref{pi-alt} to show that $\pi((1+\eps)x) - \pi(x)$ goes to infinity as $x \to \infty$.
\end{proof}
\begin{proposition}\label{mun} We have $|\sum_{n \leq x} \frac{\mu(n)}{n}| \ll 1$.
\end{proposition}
\begin{proof} From M\"obius inversion $1_{n=1} = \sum_{d|n} \mu(d)$ and summing we have
\begin{proof}
From M\"obius inversion $1_{n=1} = \sum_{d|n} \mu(d)$ and summing we have
$$ 1 = \sum_{d \leq x} \mu(d) \lfloor \frac{x}{d} \rfloor$$
for any $x \geq 1$. Since $\lfloor \frac{x}{d} \rfloor = \frac{x}{d} + O(1)$, we conclude that
$$ 1 = x \sum_{d \leq x} \frac{\mu(d)}{d} + O(x)$$
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\begin{proposition}\label{mu-pnt} We have $\sum_{n \leq x} \mu(n) = o(x)$.
\end{proposition}
\begin{proof} From the Dirichlet convolution identity
\begin{proof}
\uses{mun, StrongPNT}
From the Dirichlet convolution identity
$$ \mu(n) \log n = - \sum_{d|n} \mu(d) \Lambda(n/d)$$
and summing we obtain
$$ \sum_{n \leq x} \mu(n) \log n = - \sum_{d \leq x} \mu(d) \sum_{m \leq x/d} \Lambda(m).$$
Expand All @@ -114,10 +134,13 @@
\end{proof}
\begin{proposition} We have $\sum_{n \leq x} \lambda(n) = o(x)$.
\begin{proposition} \label{lambda-pnt}
We have $\sum_{n \leq x} \lambda(n) = o(x)$.
\end{proposition}
\begin{proof} From the identity
\begin{proof}
\uses{mu-pnt}
From the identity
$$ \lambda(n) = \sum_{d^2|n} \mu(n/d^2)$$
and summing, we have
$$ \sum_{n \leq x} \lambda(n) = \sum_{d \leq \sqrt{x}} \sum_{n \leq x/d^2} \mu(n).$$
Expand All @@ -127,3 +150,5 @@
$$ \sum_{n \leq x} \lambda(n) = O(\eps x) + O_\eps(x^{1/2}).$$
Sending $\eps \to 0$ we obtain the claim.
\end{proof}
%%-/
2 changes: 1 addition & 1 deletion blueprint/blueprint.tex
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Expand Up @@ -70,7 +70,7 @@ \section{Strong PNT}

\chapter{Elementary Corollaries}

\input{consequences.tex}
\input{Consequences.tex}


\end{document}
13 changes: 8 additions & 5 deletions blueprint/wiener.tex
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Expand Up @@ -92,7 +92,8 @@
\begin{proof} This is a standard result in Fourier analysis.
\end{proof}

\begin{corollary} If $\Psi: (0,\infty) \to \C$ is smooth and compactly supported away from the origin, then, then
\begin{corollary}\label{WienerIkeharaSmooth}
If $\Psi: (0,\infty) \to \C$ is smooth and compactly supported away from the origin, then, then
$$ \sum_{n=1}^\infty f(n) \Psi( \frac{n}{x} ) = A x \int_0^\infty \Psi(y)\ dy + o(x)$$
as $u \to \infty$.
\end{corollary}
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Now we add the hypothesis that $f(n) \geq 0$ for all $n$.

\begin{proposition}
\label{prop:smooth-ury}
\label{WienerIkeharaInterval}
For any closed interval $I \subset (0,+\infty)$, we have
$$ \sum_{n=1}^\infty f(n) 1_I( \frac{n}{x} ) = A x |I| + o(x).$$
\end{proposition}
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Use Lemma \ref{smooth-ury} to bound $1_I$ above and below by smooth compactly supported functions whose integral is close to the measure of $|I|$, and use the non-negativity of $f$.
\end{proof}

\begin{corollary} We have
\begin{corollary}\label{WienerIkehara}
We have
$$ \sum_{n\leq x} f(n) = A x |I| + o(x).$$
\end{corollary}



\begin{proof}
\uses{prop:smooth-ury}
\uses{WienerIkeharaInterval, cheby}
Apply the preceding proposition with $I = [\varepsilon,1]$ and then send $\varepsilon$ to zero (using \eqref{cheby} to control the error).
\end{proof}



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