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Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions
14
votes
Congruence equation and quadratic residue
An element $x$ of $\bar{\mathbb{F}_p}$ satisfies
$$\sum_{k=0}^{M}{M \choose k}^2x^k=0$$
iff the elliptic curve given by the equation $Y^2 = X(X-1)(X-x)$ is supersingular : see the paragraph on the Leg …
14
votes
Accepted
A simple number theory confirmation
Yes. If we set $\alpha = (a+b)/2$ and $\beta=(a-b)/2$, then the lattice generated by the four vectors
$$
\binom{\alpha}{\beta},\binom{-\beta}{\alpha},\binom{\alpha+\beta}{\alpha -\beta},\binom{\beta …
7
votes
0
answers
441
views
Closed form evaluation of the sum of the Legendre symbol over an interval ?
Let $p$ be a prime with $p \equiv 3 \mod 4$, $p \neq 3$, with its associate Legendre symbol $\left( \frac{.}{p} \right)$, and let $h$ be the class number of $\mathbb{Q} ( i \sqrt{p} )$. If $x \mapsto …
0
votes
Special divisor function summation
This is also directly related to the size of $\sum_{n \leq X} \mu(n)$ as follows :
Assume that the estimate $\sum_{n \leq X} \frac{\mu(n)}{n} = O(\varepsilon(X))$ holds for some non increasing functi …
10
votes
2
answers
2k
views
Prime numbers in arithmetic progressions : uniformity with respect to the modulus
Most of the proofs of Dirichlet's theorem on primes in arithmetic progressions actually give a Mertens-like theorem, and then the (weaker) statement
Chebyshev-like bound : if $(a,q) = 1$ then
…
10
votes
Accepted
Changing values of digits of an algebraic irrational number
Let $x_j = \sum_{n \geq 1} \mathrm{1}_{a_n=j} 3^{-n}$. Then
$$
x_0 + x_1 + x_2 = \frac{1}{2} \\
x_1 + 2x_2 = x \\
x_0 + 2x_1 = f(x).
$$
If $x$ and $f(x)$ are algebraic then the equations above would …
1
vote
Geometry of numbers argument: counting integers with some linear condition
I can show the (exact) inequality
$$(*) \ \ \ \ \ \ V(Z_1) \geq \left(\frac{Z_1}{Z_2} \right)^2 V(Z_2) \ \ \quad (\frac{2}{A} \leq Z_1 \leq Z_2 \leq \frac{A}{2}), $$
for a smoothed version of $U$ def …
7
votes
3
answers
413
views
Covering a (hyper)cube with lines
Let $K_n$ be the sets of vectors $x \in \mathbb{Z}^d $ with each coordinates $x_i$ between $1$ and $n$. For any subset $A$ of $K_n$, let $S(A)$ be the set of points $x \in K_n$ which are on some line …
2
votes
An estimate of the sum related to primes
By juan's answer above, one only needs to show $\sum_{p \leq e^{\frac{2}{\delta}}} \frac{1}{p^{1-\delta}} \leq \log \frac{1}{\delta} + O(1) $. But by estimating $p^{\delta} = 1 + O( \delta \log p )$, …
8
votes
Accepted
Averaging $2^{\omega(n)}$ over a region
Your guess is correct. Since $2^{\omega(n)} = \sum_{d | n} \mu^2(d)$ one has
$$
S = \sum_{(a,b,c) \in R(X)} 2^{\omega(4ac-b^2)} = \sum_{d \leq X} \mu^2(d) |R_d(X)|
$$
where $R_d(X)$ is the set of inte …
2
votes
Accepted
Computability of a relation connected to the discrete logarithm
Of course since $R = \{ (a,b) \in \mathbb{N} \times \mathbb{N} \ | \ (a=1) \implies (b=1) \} $.
Indeed for $a > 1$ one can take $n = a^k-b$ for $k$ large enough.
9
votes
Accepted
Estimates for $\sum_{n\leq x} d(n)^a$
One has $S_a(x) \sim C(a) x (\log x)^{2^a -1}$ where
$$
C(a) = \Gamma(2^a)^{-1} \prod_p \left( 1 - \frac{1}{p} \right)^{2^a} \left( \sum_{k \geq 0} \frac{(k+1)^a}{p^k}\right).
$$
This follows for exam …
5
votes
Accepted
Polynomials $P$ with integer roots near to $X^{\mathrm{deg}(P)}$
One can take $r = 1 + \frac{d(d-1)}{2}$.
Indeed, one can consider the map
$$
(\alpha_i)_{i=1}^r \in [|1,N|]^{r} \mapsto (\sum_{i=1}^r \alpha_i^k)_{k=1}^{d-1} \in \prod_{i=1}^{d-1} [|1,rN^k|].
$$
The …
9
votes
Accepted
Asymptotic estimate of double summation
Using the decomposition
$$
H(x) := \sum_{a \leq x} \frac{1}{a} = \log(x) + \gamma - \frac{\psi(x)}{x} + \int_{x}^{+\infty} \frac{\psi(t) d t}{t^2},
$$
where $\psi(t) = \{ t \} - \frac{1}{2}$, one ge …
4
votes
Large prime divisors in small intervals
You can simplify Ramachandra's method by bounding the last sum of p.305 using Brun-Titchmarsh inequality (or Montgomery & Vaughan error-term free version of it) instead of Van der Corput's method + Se …