All Questions
16 questions
19
votes
4
answers
1k
views
Generalization of a mind-boggling box-opening puzzle
Motivation. Suppose we are given $6$ boxes, arranged in the following manner:
$$\left[\begin{array}{ccc} 1 & 2 & 3 \\ 4 & 5 & 6 \end{array}\right]$$
Two of these boxes contain a ...
- 48.9k
1
vote
0
answers
84
views
How can one build a min-2-wise independent small sample space from min-3-wise permutations?
I have been studying a polynomial-size set of permutations from one of my lectures. The below image, taken from the lecture notes PDF, illustrates how to construct min-3-wise permutations.
My ...
- 43
4
votes
1
answer
167
views
A probability problem in the conjugacy classes of symmetric group
Assume that $\sigma\in S_n$ has the cycle type $(p,.,p,1,..,1)$ where $p>2$ is a prime and the numbers of $1$ maybe $0$. If $\sigma_1$ and $\sigma_2$ are chosen uniformly in the conjugacy class of $...
- 253
3
votes
1
answer
135
views
Cycle counts in Ewens measure as $\theta$ diverges
For $w$ a permutation, let $c(w)$ denote the total number of cycles and $c_i(w)$ denote the number of $i$-cycles.
The Ewens measure is a one-parameter probability distribution on permutations where ...
- 1,989
3
votes
1
answer
161
views
Probability permutation in turned to cycle
Let $M$ be a $0/1$ square matrix having one $1$ per row and column (permutation matrix).
If you permute the columns and rows independently what is the probability resulting permutation matrix is a ...
- 13.9k
8
votes
2
answers
475
views
Random permutations without double rises (avoiding consecutive pattern $\underline{123}$)
A permutation avoiding a consecutive pattern $\underline{123}$ is permutation
$\pi = \pi_1 \pi_2 \ldots \pi_n$ with the property that there does not exists $i \in [1, n-2]$
such that $\pi_i < \pi_{...
- 345
12
votes
2
answers
947
views
How rare are unholey permutations?
For $S\subset [n]:=\{1,2,\dotsc,n\}$, define $\delta(S)$ to be the number of $m\in S$ such that $m+1\notin S$.
Given a permutation $\pi$ of $[n]$, we define the holeyness $D(\pi)$ of $\pi$ as being $...
- 20.2k
4
votes
0
answers
216
views
How frequent are permutations with small interleaving?
For $S\subset [n]:=\{1,2,\dotsc,n\}$, define $\delta(S)$ to be the number of $m\in S$ such that $m+1\notin S$.
Let $\pi$ be a permutation of $[n]$. For simplicity, assume that $\pi$ is an $n$-cycle. ...
- 20.2k
3
votes
1
answer
647
views
Regarding left-to-right minima
Let $\rho$ be a permutation on $[1,n]$ and $l_i$ be the number of left-to-right minima in $\rho_{i\ldots n}$, I know that for a random permutation $E[l_1] = H_n$ (the $n$-th Harmonic number) but is ...
- 31
8
votes
1
answer
227
views
Distribution of entries of a doubly-sorted random matrix
Take an $n \times n$ random matrix whose entries are i.i.d. with uniform distribution in $[0,1]$. Look at the sums of the elements of each row and then permute the rows so that these sums form an ...
- 2,479
1
vote
1
answer
101
views
Probability of seeing m nonzero bits in off any d consecutive bits in a circle of n bits
Suppose n bits are arranged circularly with given condition that random k of them are 1 and rest 0, and all possible d consecutive bits (total n possibilities) are looked at, what is the probability ...
- 11
22
votes
2
answers
1k
views
Laws of Iterated Logarithm for Random Matrices and Random Permutation
The law of iterated logarithm asserts that if $x_1,x_2,\dots$ are i.i.d $\cal N(0,1)$ random variables and $S_n=x_1+x_2+\cdots+x_n$, then
$$\limsup_{n \to \infty} S_n/\sqrt {n \log \log n} = \sqrt 2, $...
- 24.7k
3
votes
0
answers
251
views
Permutations & Balanced Distribution
I would like to implement a form of consistent hashing using a set of permutations.
The rules are as follows:
I have Y=~32 buckets and X items. Buckets may be "alive" or "dead". Items are to be ...
- 31
4
votes
1
answer
1k
views
Probabilty of two permutations having common elements?
What is the probability of two permutations on set X of size m (i.e. |X|=m) having at least n points of intersection? By this I mean that if two permutations, which I'll call g(x) and h(x), map a ...
- 55
2
votes
1
answer
467
views
Distribution on permutations derived from probability of pairwise orderings
A followup question to Probability estimates for pairwise majority votes - I think it doesn't actually give an answer in any terribly precise sense, but it would give something I'd be happy to use in ...
- 1,331
19
votes
9
answers
3k
views
How can I generate random permutations of [n] with k cycles, where k is much larger than log n?
I've been thinking a lot lately about random permutations. It's well-known that the mean and variance of the number of cycles of a permutation chosen uniformly at random from Sn are both ...
- 14k