# Questions tagged [nt.number-theory]

Questions in number theory

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### Complexity of exponential function

We know that the exponential function $\exp(x,y) = x^y$ over natural numbers is not computable in polynomial time, because the size of the output is not polynomially bounded in the size of the inputs. ...
1answer
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### Efficiently computable function as a counter-example to Sarnak's Mobius conjecture

Recently, Gil Kalai and Dick Lipton both wrote nice articles on an interesting conjecture proposed by Peter Sarnak, an expert in number theory and the Riemann Hypothesis. Conjecture. Let $\mu(k)$ ...
3answers
2k views

### complexity of greatest common divisor (gcd)

Consider the following counting problem (or the associated decision problem): Given two positive integers encoded in binary, compute their greatest common divisor (gcd). What is the smallest ...
6answers
2k views

### Is there a natural problem on the naturals that is NP-complete?

Any natural number can be regarded as a bit sequence, so inputting a natural number is the same as inputting a 0-1 sequence, so NP-complete problems with natural inputs obviously exist. But are there ...
2answers
1k views

### How hard is it to count the number of factors of an integer?

Given an integer $N$ of length $n$ bits, how hard is it to output the number of prime factors (or alternatively number of factors) of $N$? If we knew the prime factorization of $N$, then this would ...
2answers
1k views

### Finding a prime greater than a given bound

Is a deterministic polynomial-time algorithm known for the following problem: Input: a natural number $n$ (in binary encoding) Output: a prime number $p > n$. (According to a list of open ...
2answers
1k views

### Complexity of factoring in number fields

What is known about the computational complexity of factoring integers in general number fields? More specifically: Over the integers we represent integers via their binary expansions. What is the ...
4answers
12k views

### How to check if a number is a perfect power in polynomial time

The first step of the AKS primality testing algorithm is to check if the input number is a perfect power. It seems that this is a well known fact in number theory since the paper did not explain it in ...
2answers
2k views

### Implications of proof of abc conjecture for cs theory

What implications would a proof of the abc conjecture have for tcs? http://quomodocumque.wordpress.com/2012/09/03/mochizuki-on-abc/
5answers
764 views

### Easy problems with hard counting versions

Wikipedia provides examples of problems where the counting version is hard, whereas the decision version is easy. Some of these are counting perfect matchings, counting the number of solutions to $2$-...
2answers
1k views

### Decidability of diophantine equations over {=, +, gcd}

It is well-known that polynomial diophantine equations are undecidable (Hilbert's 10th problem): that is, given a quantifier-free formula over the language $\{=, +, \cdot, 1\}$ (of equality, addition, ...
1answer
463 views

### Is prime-counting function #P-complete?

Recall $\pi(n)$ the number of primes $\le n$ is the prime-counting function. By "PRIMES in P", computing $\pi(n)$ is in #P. Is the problem #P-complete? Or, perhaps, there is a complexity reason to ...
4answers
686 views

### How to obtain the unknown values $a_i,b_j$ given an unordered list of $a_i-b_j\mod N$?

Can anyone help me with the following problem? I want to find some values $a_i,b_j$ (mod $N$) where $i=1,2,…,K, j=1,2,…,K$ (for example $K=6$), given a list of $K^2$ values that correspond to the ...
1answer
827 views

### Is solving systems of equations modulo $k$ in $\mathsf{coMod}_k\mathsf L$ for $k$ composite?

I'm interested in the complexity of solving linear equations modulo k, for arbitrary k (and with a special interest in prime powers), specifically: Problem. For a given system of $m$ linear ...
1answer
964 views

### Why does Odlyzko improvement of Shor's Algorithm reduces the number of trials to $O(1)$

In his 1995 paper Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer, Peter W. Shor discusses an improvement on the order-finding part of his ...
0answers
329 views

### Does Factoring have a Statistical Zero Knowledge Proof?

The title should be pretty self-explanatory, but to be more precise, consider the decision version of factoring, which is given input $(x,k)$, where $x$ and $k$ are binary encodings of integers, to ...
2answers
929 views

### Collatz Conjecture & Grammars / Automata

I was wondering if there is a good bibliography of attempts to investigate the Collatz conjecture as a formal grammar? (or any other attempts in the CS community to deal with this class of generative ...
2answers
4k views

### What is the “nearest” problem to the Collatz conjecture that has been successfully resolved?

I am interested in the "nearest" (and "most complex") problem to the Collatz conjecture that has been successfully solved (which Erdos famously said "mathematics is not yet ...
0answers
440 views

1answer
337 views

### Algorithm to compute distance between powers

Given coprime $a, b$, can you quickly compute $$\min_{x, y > 0} |a^x - b^y|$$ Here $x, y$ are integers. Obviously taking $x = y = 0$ gives an uninteresting answer; in general how close can these ...
1answer
439 views

### Formalizing the “no formula for primes” intuition

I was trying to formalize the intuition is that there is no formula for primes, and this is my best attempt: Conjecture: There is no $O(n^2)$ expected time randomized algorithm to generate $\ge n$-...
2answers
789 views

### Is square removal easier than factoring?

It seems to me that the square removal task can be reduced to the factoring task, but that there is no way to reduce factoring to square removal. Is there a way to make this "feeling" more precise, i....
1answer
240 views

2answers
179 views

### Difference Sets

Suppose we have a set $$P=\{p_1,p_2,...,p_K\}$$ where $$1\leq p_k\leq N , k=1,...,K \qquad \& \quad p_k \in \mathbb{N}$$ and $p_k$'s are distinct. We calculate the differences as: d=p_i-p_j\mod ...