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fedja
  • Member for 13 years
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49 votes

What is the simplest lower bound on prime counting functions proof wise?

42 votes

What's the sign of $\det\left(\sqrt{i^2+j^2}\right)_{1\le i,j\le n}$?

23 votes
Accepted

Math contest: Find number of roots of $F(x)=\frac{n}{2}$ involving a strange integral.

22 votes

If $\int_{\mathbb R^2} \frac{\vert f(x)-f(y)\vert}{\vert x-y\vert^2}dxdy<+\infty$ then $f$ is a.e. constant

20 votes

Level of Rigor in Mathematical Physics

18 votes
Accepted

Is the series $\sum_{i=k}^\infty\frac{\sin\left(\frac{x}{i}\right)}{i}$ bounded?

17 votes

Optimizing response times of an ambulance corp: short-term versus average

15 votes

Why can't $p^p-(p-1)^{p-1}=n^2$ be a square?

14 votes

How to say $(a,b]$ and $[a,b)$ in English?

13 votes

A Knight and Knave Problem

12 votes
Accepted

Is it possible to characterize completeness of a normed vector space by convergence of Neumann series?

11 votes

$w^4+(w')^2 = g(t)$

11 votes
Accepted

Strange inequality involving *nested* binomial coefficients and combinatorial interpretation

11 votes
Accepted

Given $n+1$ points, bound the product of the distances from one of them

10 votes
Accepted

About $2$-periodic continuous solutions of $f(x)+f(x+1)=f(2x+1)$

10 votes
Accepted

Is the matrix square root uniformly continuous?

9 votes
Accepted

Find function $f(x)$ satisfying $\int_{0}^{\infty} \frac{f(x)}{1+e^{nx}}dx=0$

9 votes
Accepted

Is this function decreasing in $x$?

9 votes
Accepted

Is the Laplacian surjective on $C_0^{\infty}$?

9 votes
Accepted

Method of dominant balance

8 votes

Why is "for all $x\in\varnothing$, $P(x)$" true, but "there exists $x\in\varnothing$ such that $P(x)$" false?

8 votes

Projection of tetrahedron to complex plane

8 votes
Accepted

Possibility that all lights $\mathbf{X}=(X_1,X_2,\cdots)$ turn off again with every time turn a light with its number $n\sim\text{geom}(\frac{1}{2})$.

8 votes
Accepted

An inequality $ k\frac{\sum_{i\neq j} x_i x_j ( (1-x_i-x_j)^{k-1}- (1-x_i)^k(1-x_j)^k)}{\sum_{i=1}^n x_i (1-(1-x_i)^k)} \leq 2$

8 votes
Accepted

Finding $\int_{0}^\infty f(u)du$ where $f$ solves $\frac{\pi}{2}f(u) = \frac{1}{1+u^2} - \int_{0}^\infty \frac{f(v) dv}{4+(u-v)^2}$

8 votes

Minimum number of straight lines to cover $n \times n$ grid?

7 votes

A question about Cauchy product

7 votes

How long does it take to get to "Olympiad-Bronze-level" of math problem solving ability from no competition experience?

7 votes

Does real analysis have new theorems, or is it just a collection of proofs of old calculus theorems?

7 votes

What is the coefficient of the $x^3$ term in the expansion of $(x^2+x-5)^7$ (See details)?

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