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This tag is used if a reference is needed in a paper or textbook on a specific result.
1
vote
1
answer
105
views
Question about properties of affine varieties defined by bihomogeneous polynomials
Let $F_1(\mathbf{x}, \mathbf{y}), \ldots, F_r(\mathbf{x}, \mathbf{y})$ be bihomogeneous polynomials with rational coefficients with bidegree $(d_1, d_2)$, which means
$$
F_i( s x_1, \ldots, s x_{n_1} …
0
votes
0
answers
93
views
A way to bound $\sum_{1 \leq n \leq X} \min ( \| \alpha n \|^{-1} , X/n)$?
Let $\alpha$ be a real number and $|| \cdot ||$ be the distance to
the nearest integer.
I want to find a non-trivial upper bound for
$$
\sum_{1 \leq n \leq X} \min ( || \alpha n ||^{-1} , X/n),
$$
w …
2
votes
1
answer
706
views
rank of a linear combination of matrices
Let $A_1,..., A_s \in M_n(\mathbb{R})$ be symmetric matrices and suppose they are linearly independent over $\mathbb{R}$. This means that
$$
m = \min_{(c_1, ..., c_s) \in \mathbb{R}^s \backslash \{0\} …
4
votes
4
answers
540
views
An upperbound for divisor function squared on a short interval
Let $d(n)$ be the divisor function defined by $d(n) = \sum_{m|n} 1$. I am in need of estimate of the following type:
$$
\sum_{Q \leq n \leq Q + H} d^2(n) \ll H (\log (Q + H))^T
$$
where $T$ can be any …
1
vote
0
answers
143
views
Estimating the sum of Dirichlet character $\sum_{0 \leq x < q} \chi(F(x))$ where $F(x)$ is a...
Let $q \in \mathbb{N}$ and $\chi$ a Dirichlet character mod $q$. Let $F(x)$ be a polynomial with integer coefficients. I was wondering if a bound for the following sum was available or not:
$$
\sum_{0 …
3
votes
1
answer
460
views
Reference for explicit formula for $\sum_n \Lambda(n) \chi(n)$ with smooth weights
Let $\Lambda$ be the von Mangoldt function and $\chi$ a primitive character mod $q$, then we have the explicit formula
$$
\sum_{n \leq X} \Lambda(n) \chi(n) = \delta_{\chi} X - \sum_{ |Im \ \rho| \leq …
5
votes
1
answer
351
views
How can I prove that $(n-1)$-dimensional manifold is not contained in a $(n-2)$-dimensional ...
I am having trouble proving the following statement, which I think is true (and possibly very basic). Let $M$ be a real differentiable manifold of dimension $(n-1)$ sitting inside $\mathbb{R}^n$. Let …
3
votes
1
answer
246
views
number of integers $n$ with $\|n \alpha \|$ small?
Let $\alpha \in \mathbb{R}$ and $N$ a positive integer. I am interested in the quantity
$$
D(\alpha, N) := \# \{ n \in [1, N]: \| n \alpha \| < 1/N \},
$$
$\| x \|$ denotes the distance to the closes …
1
vote
2
answers
262
views
Average value of a fractional part of a function
Let $f(x): \mathbb{R} \to \mathbb{R}_{\geq 0}$ be a smooth function. I am interested in estimating
sums of the form
$$
\sum_{ A < n \leq B } \{ f(n)\}
$$
where $\{ c \}$ denotes the fractional part of …
1
vote
1
answer
439
views
Distribution of Mobius function
Let $\mu(n)$ be the Mobius function.
Let us define $\mu^+(n)$ to be $\mu(n)$ if $\mu(n)>0$ and $0$ otherwise. Is there a known asymptotic formula for
$$
\sum_{n \leq N} \mu^+(n),
$$
and similarly f …
0
votes
1
answer
204
views
Are there Vaughn's identity type decompositions for other arithmetic functions?
Vaughn's identity is a useful way to decompose the von Mangoldt function $\Lambda(n)$ into Type I and Type II components, and this is used in many problems involving prime numbers. I was wondering if …
10
votes
1
answer
1k
views
A generalisation of theorem of Landau on sum of two squares?
Let
$r(B)$ be the number of integers $1 \leq n \leq B$ such that $n = x^2 + y^2$ for some $x, y \in \mathbb{Z}.$
Then it is a known theorem of Landau that
$$
r(B) \sim C \frac{B}{\sqrt{\log B}}
$$
f …
-1
votes
3
answers
296
views
Reference for Siegel-Walfisz Theorem under GRH
Let $\Lambda$ be the von Mangoldt function.
I think the following is known to hold under GRH: Given any $q \geq 1$, $(a,q)=1$, and $X \geq 1$, we have
$$
\sum_{\substack{1 \leq n \leq X \\ n \equiv …
4
votes
1
answer
510
views
Siegel-Walfisz Theorem with smooth weights
Let
$$\psi(x;q,a)=\sum_{n\leq x\atop n\equiv a\pmod q}\Lambda(n)$$
where $\Lambda$ denotes the von Mangoldt function and $\phi$ to be Euler's totient function.
Then the Siegel-Wafisz theorem states t …
10
votes
1
answer
539
views
Sidon sets of $\mathbb{Z}/p\mathbb{Z}$
A set $S \subseteq \mathbb{Z}/p\mathbb{Z}$ is called a Sidon set if given $a, b, c, d \in S$ and $a+ b = c+ d$, then $\{a, b\} = \{c,d\}$. I was interested in knowing about the largest possible Sidon …