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Enumerative combinatorics, graph theory, order theory, posets, matroids, designs and other discrete structures. It also includes algebraic, analytic and probabilistic combinatorics.

0 votes

Number of tuples satisfying the following condition

If you just care about asymptotics, then you can use central limit theorem or LDP techniques to get an exponential estimate. Here is how: let $x_1, \ldots, x_M$ be iid uniform random variables in $[0, …
John Jiang's user avatar
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2 votes

Linear Recurrence Relations in 2 Variables with Variable Coefficients

I don't think constant is the only tempered growth solution to your 2d recurrence. Essentially the recurrence needs a 1-dimensional subspace in $\mathbb{Z}^2$ of boundary conditions. Then your recurre …
John Jiang's user avatar
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3 votes

What is the probability that every pair of students is at some point in the same classroom?

The answer is given in terms of inclusion exclusion principle, much as the solution for coupon collector's problem. Let $p_t$ be the probability that at time $t$ there are still two vertices with no e …
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3 votes
1 answer
242 views

Bounding the success time of a coupon collector like problem

Consider the complete graph on $n$ vertices. Each step, one chooses one of the $\binom{n}{2}$ edges iid uniformly at random. Say a sequence of choice is successful if there is some permutation of the …
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1 vote
0 answers
206 views

understanding some derivation in random XORSAT problem

This question is concerned about the paper "The 3-XORSAT threshold" by O. Dubois, J.Mandler. Here is the link: http://dx.doi.org/10.1016/S1631-073X(02)02563-3 Basically one would like to know when is …
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0 votes
1 answer
111 views

how to find a sequence of digits in base b such that each consecutive block of size k appear...

My question is most precisely stated in the title. As an example, if we consider base 10, and k=4, then I am asking, is it possible to have a sequence of length 10^4 + 3, such that each 4 digit number …
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2 votes

Some questions concerning a random number process

The process described is also known as the stick-breaking process for sampling the cycle type of a uniformly chosen permutation in $S_n$. So we have the set $[n]$ and we want to choose a uniformly …
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3 votes
1 answer
365 views

counting the number of ordered pairs in a permutohedron

Recall that a permutohedron is a graph on the set of permutations $S_n$ with an edge between $\sigma$ and $\tau$ if they differ by one adjacent transposition: $\tau = (i,i+1) \circ \sigma$ for some $i …
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2 votes
1 answer
117 views

A problem about the existence of increasing coloring groups

Got stuck on this one for months. Given a sequence of non decreasing positive integers $a_1, .., a_n$, let there be $a_i$ balls labeled the number i, for each $1 \leq i \leq n$. Suppose there is a k c …
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17 votes
4 answers
1k views

universality of Macdonald polynomials

I have been recently learning a lot about Macdonald polynomials, which have been shown to have probabilistic interpretations, more precisely the eigenfunctions of certain Markov chains on the symmetri …
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5 votes
1 answer
168 views

An extension of Hadamard maximum determinant problem

Consider the Vandermonde product $\prod_{1\le j < k \le n} |z_j - z_k|$. It is well-known that under the constraint $|z_j| \le 1$ for all $j$, the product is maximized at a picket fence configuration …
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2 votes

Applications of measure, integration and Banach spaces to combinatorics

Markov chains on symmetric groups converging to various distributions other than uniform provide a fertile ground for the marriage between modern combinatorics such as Macdonald polynomials and hard a …
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2 votes
0 answers
627 views

analogues of power sum polynomials for symmetric Laurent polynomials

To deal with root systems of type B C D, one needs to understand symmetric Laurent polynomials $\Lambda$. I am wondering if the naive definition of power sum symmetric Laurent polynomials form a basis …
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2 votes
0 answers
104 views

Bounding Schur polynomials of a particular shape

Consider Schur polynomials $s_\lambda$ with $\lambda = (2m, m, m, \ldots, m, 0)$ and $\ell(\lambda) = n$ (that is, $\lambda$ has $n$ rows). Here $m \gg n$, which, for the sake of concreteness, let's a …
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2 votes

What is known about zero-sets of Schur polynomials?

For $k :=|\lambda| \ge r$, the statement that all $s_\lambda(x_1, \ldots, x_r)$ vanish is equivalent to all the elementary polynomials $e_j(x_1, \ldots, x_r) := \sum_{i_1 < \ldots < i_j} x_{i_1} \ldot …
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