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3 edited body

Let $x$ be a real number and $N$ a positive integer. Define

$E(N,\delta) = \{(p,q) \in \mathbb{Z}^2: |p + - q x| \leq \frac{\delta}{N}, |p|, |q| \leq N \}$,

i.e., the set of solutions to rational approximation of $x$ with accuracy $\frac{\delta}{N}$.

I am interested in the behavior of the cardinality of $E(N,\delta)$. Question:

For which $x$ do we have $|E(N,\delta)| \leq c(\delta) N$ where $c(\delta) \to 0$ as $\delta \to 0$?

Of course $x$ has to be irrational. Is this true for all irrational $x$? I am very unfamiliar with Diophantine approximation. I googled a bit and found that Schmidt proved that $|E(N,\delta)| = O(\log N)$ for a.e. $x$. Lang proved that this holds for all quadratic irrational $x$. But $O(\log N)$ is much stronger than what I asked, which is even weaker than $o(N)$.

(One further question: if we replace $\frac{1}{N}$ by $\frac{1}{N^{1+\epsilon}}$, how does the number of solutions behave?)

2 corrected spelling

Let $x$ be a real number and $N$ a positive integer. Define

$E(N,\delta) = \{(p,q) \in \mathbb{Z}^2: |p + q x| \leq \frac{\delta}{N}, |p|, |q| \leq N \}$,

i.e., the set of solutions to rational approximation of $x$ with accurracy accuracy $\frac{\delta}{N}$.

I am interested in the behavior of the cardinality of $E(N,\delta)$. Question:

For which $x$ do we have $|E(N,\delta)| \leq c(\delta) N$ where $c(\delta) \to 0$ as $\delta \to 0$?

Of course $x$ has to be irrational. Is this true for all irrational $x$? I am very unfamiliar with Diophantine approximation. I googled a bit and found that Schmidt proved that $|E(N,\delta)| = O(\log N)$ for a.e. $x$. Lang proved that this holds for all quadratic irrational $x$. But $O(\log N)$ is much stronger than what I asked, which is even weaker than $o(N)$.

(One further question: if we replace $\frac{1}{N}$ by $\frac{1}{N^{1+\epsilon}}$, how does the number of solutions behave?)

1

# number of solutions of diophantine approximation

Let $x$ be a real number and $N$ a positive integer. Define

$E(N,\delta) = \{(p,q) \in \mathbb{Z}^2: |p + q x| \leq \frac{\delta}{N}, |p|, |q| \leq N \}$,

i.e., the set of solutions to rational approximation of $x$ with accurracy $\frac{\delta}{N}$.

I am interested in the behavior of the cardinality of $E(N,\delta)$. Question:

For which $x$ do we have $|E(N,\delta)| \leq c(\delta) N$ where $c(\delta) \to 0$ as $\delta \to 0$?

Of course $x$ has to be irrational. Is this true for all irrational $x$? I am very unfamiliar with Diophantine approximation. I googled a bit and found that Schmidt proved that $|E(N,\delta)| = O(\log N)$ for a.e. $x$. Lang proved that this holds for all quadratic irrational $x$. But $O(\log N)$ is much stronger than what I asked, which is even weaker than $o(N)$.

(One further question: if we replace $\frac{1}{N}$ by $\frac{1}{N^{1+\epsilon}}$, how does the number of solutions behave?)