# Tagged Questions

**5**

votes

**2**answers

402 views

### Complexity of Membership-Testing for finite abelian groups

Consider the following abelian-subgroup membership-testing problem.
Inputs:
A finite abelian group $G=\mathbb{Z}_{d_1}\times\mathbb{Z}_{d_1}\ldots\times\mathbb{Z}_{d_m}$ with ...

**4**

votes

**1**answer

276 views

### Hermit H-machines

I call an H-machine a machine that can be connected to turing machines and that takes as input a natural integer n and instantly returns the n'th digit of the mathematical constant H.
Is there a ...

**7**

votes

**1**answer

591 views

### Finding colinear points in F_q^n

Forgive me if this is well known, it's not really my field, but it's a problem I've run across and thought about a bit.
Let $\mathbb{F}_q$ be a finite field with $q$ elements, let $n\ge2$, and let ...

**2**

votes

**0**answers

258 views

### Reducing factoring prime products to factoring integer products (in average-case)

My question is about the equivalence of the security of various candidate one-way functions that can be constructed based on the hardness of factoring. (This question has been asked also in the CS ...

**8**

votes

**2**answers

400 views

### Efficient computation of the least fraction with square denominator greater than the square root of 2.

The least rational number greater than $\sqrt{2}$ that can be written as a ratio of integers $x/y$ with $y\le10^{100}$ can be found in a moment using a little Python program. Can anyone write a ...

**1**

vote

**1**answer

270 views

### Computation for composition of polynomials

Let $R$ be a ring, $f(X)$ be a polynomial with coefficients in $R$ of degree $n$. It's known that for any $\alpha \in R$, one can evaluate $f$ at $\alpha$, i.e compute $f( \alpha) $ in $O(n)$ ...

**37**

votes

**2**answers

5k views

### Walsh Fourier Transform of the Möbius function

This question is related to this previous question where I asked about ordinary Fourier coefficients.
Special case: is MÃ¶bius nearly Orthogonal to Morse
!
Harold Calvin Marston Morse (24 March ...

**5**

votes

**1**answer

256 views

### Speeding the quadratic sieve with an oracle

Suppose we have an odd composite $N$ and want to find numbers $a_1,\ldots,a_k$ such that each $a_i^2$, reduced mod $N$, is $b$-smooth. Of course we can use the quadratic sieve algorithm (minus the ...

**5**

votes

**4**answers

659 views

### Reconstructing a fraction from its first digits

It is not difficult to see that any reduced fraction $\frac{p}{q}$
where $0 < p < q $ and both $p$ and $q$ have at most $N$
digits (where $N$ is a fixed integer) can be reconstructed
from its ...