47
votes
33answers
7k views
Experimental Mathematics
I would like to ask about examples where experimentation by computers have led to major mathematical advances.
Motivation
I am aware about a few such cases and I think it will b …
12
votes
2answers
971 views
The behavior of a certain greedy algorithm for Erdős Discrepancy Problem
Let $N$ be a positive integer.
We want to find a completely multiplicative functions f(n) with values $\pm 1$ for $n \le N$ such that the discrepancy
$$D=\max_{n \le N} |{\sum_{i …
58
votes
5answers
6k views
Why does the Riemann zeta function have non-trivial zeros?
This is a very basic question of course, and exposes my serious ignorance of analytic number theory, but what I am looking for is a good intuitive explanation rather than a formal …
26
votes
6answers
4k views
How many surjections are there from a set of size n?
It is well-known that the number of surjections from a set of size n to a set of size m is quite a bit harder to calculate than the number of functions or the number of injections. …
18
votes
3answers
806 views
The probability for a sequence to have small partial sums
The question
Let $a_1,a_2,\dots,a_n$ be a sequence whose entries are +1 or -1. Let t be a parameter. My question is to give an estimate for the number of such sequences so that
…
22
votes
5answers
2k views
Partial sums of multiplicative functions
It is well known that some statements about partial sums of multiplicative functions are extremely hard. For example, the Riemann hypothesis is equivalent to the assertion that |&m …
11
votes
3answers
1k views
An elementary number theoretic infinite series
For a positive integer k, let d(k) be the number of divisors of k. So d(1)=1, d(p) =2 if p is a prime, d(6)=4, and d(12)=6.
What is the precise asymptotics of SUM_{k=1}^n 1/(kd(k …
26
votes
3answers
1k views
Improving a sequence of 1s and -1s
Suppose you take a $\pm 1$ sequence and you want to "improve it" by taking pointwise limits of translates. What properties can you guarantee to get in the limit?
Two examples ill …
11
votes
0answers
773 views
A question about Mobius inversion
I don't know how precise I can make this question. I want to know whether there is a theorem that says that a certain phenomenon always happens, but I think the best I can do in or …
7
votes
2answers
715 views
Analytic continuation of Dirichlet series with completely multiplicative coefficients of modulus 1
A sequence $a_n \in \mathbb{T}$ ($n \geq 1$) satisfying $a_{mn} = a_m a_n$ for all $m, n \geq 1$ defines a Dirichlet series $f(s) = \sum_n a_n n^{-s}$, absolutely convergent for $\ …
11
votes
0answers
432 views
Making a character small at a reciprocal
The following question emerged from thinking about the Erdős discrepancy problem. I don't know whether an answer would be directly helpful, but it might, and in any case I fin …
10
votes
1answer
461 views
Is this a well-known probabilistic model?
While I was thinking about the Erdős discrepancy problem, the following random walk model arose rather naturally. You fix a positive integer k, and you take a random step of 1 …
4
votes
2answers
262 views
Finding the codomain of a monoid homomorphism
We have a monoid M, and a function $f: M \rightarrow \{0, 1\}$. We're promised that this function factors through a (surjective) homomorphism to a finite abelian group (considered …

