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5
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0answers
99 views
Has Reifegerste's Theorem on RSK and Knuth relations received a slick proof by now?
For the notations I am using, I refer to the Appendix at the end of this post.
Here is what, for the sake of this post, I consider to be Reifegerste's theorem:
Theorem 1. Let $n\in\mathbb N$ and ...
6
votes
3answers
345 views
Arithmetic product of symmetric functions: why is it integral?
For every commutative ring $A$, let $\mathbf{Symm}_A$ be the ring of symmetric functions over $A$. Let $\mathbf{Symm}$ without a subscript denote $\mathbf{Symm}_{\mathbb{Z}}$.
We can define a ...
11
votes
0answers
247 views
Conjectural identities for Young symmetrizers and Young-Jucys-Murphy elements
The following questions I have found in my own notes from about 3 years ago. Unfortunately, I lost much of the context; I believe I made these conjectures reading Okounkov-Vershik, arXiv:0503040v3, ...
0
votes
2answers
247 views
Morse matching with 0-cells and (n-1)-cells
Suppose one has a Morse matching (acyclic matching) of a poset $P$ of rank $n$ in which the only unmatched cells are 0-cells and $(n-1)$-cells, the same number $k$ of each one.
If $P$ is connected ...
7
votes
0answers
116 views
Reference request: Grothendieck groups of Hecke algebras at root of unity and symmetric functions
Let $\zeta$ be an $\ell^{\text{th}}$ root of unity, and consider $H_n(\zeta)$, the (finite) Hecke algebra of type A. One can consider a dual pair of Hopf algebras arising from this data, denoted ...
8
votes
1answer
196 views
Plethysm of $\mathrm{QSym}$ into $\mathrm{QSym}$: can it be defined?
I will denote by $\Lambda$ the ring of symmetric functions, and by $\mathrm{QSym}$ the ring of quasisymmetric functions (both in infinitely many variables $x_1$, $x_2$, $x_3$, ..., both over $\mathbb ...
9
votes
2answers
202 views
How exactly does Schützenberger promotion relate to Striker-Williams promotion?
Schützenberger promotion, studied (for example) in Richard Stanley, Promotion and Evacuation, 2009, is a permutation of the set of all linear extensions of a finite poset. Since one can identify the ...
6
votes
2answers
412 views
What are the most important open problems in algebraic combinatorics? [closed]
I have seen the paper of Stanley http://math.mit.edu/~rstan/pubs/pubfiles/116.pdf
but it is quite old and many of the problems are solved. I would like to know the two or three biggest open problems ...
3
votes
1answer
157 views
Semi-planar partition monoid/algebra
Here are some beginner questions on partition algebras...
I am trying to understand the monoid called $P_k$ in Tom Halverson, Arun Ram, Partition Algebras. For the sake of simplicity, let $k$ be a ...
7
votes
3answers
499 views
bijection between number of partitions of 2n satisfying certain conditions with number of partitions of n
Suppose $\lambda = (\lambda_1,\lambda_2,.....,\lambda_k)$ is a partition of $2n$ where $n \in \mathbb N$ satisfying the following conditions:
(1) $\lambda_{k} = 1$.
(2) $\lambda_{i} - \lambda_{i+1} ...
1
vote
1answer
375 views
Combinatorial Inequality
Consider a set of $2^n-1$ non negative integers $S= ${$ a_{i,j}|1\le i\le n; 1\le j\le 2^{i-1} $} such that:
\begin{align}{}
1.\ \ &a_{i,j}\le 2^{n+1-i} \\\\
2.\ \ &a_{i,j}\le a_{i-1,j} \\\\
...
1
vote
1answer
124 views
principal specialization of projective Schur functions
Is there a nice/known formula for the (some) principal specialization of a projective (P or Q) Schur polynomial? That is, I am talking about a projective analogue of Stanley's hook content formula ...
4
votes
1answer
147 views
Is the “renormalized third comultiplication” on $\mathbf{Symm}$ integral?
Background:
For any commutative ring $R$, let $\mathbf{Symm}_R$ be the ring of symmetric functions in countably many variables $x_1$, $x_2$, $x_3$, ... over $R$. ("Symmetric functions" really means ...
0
votes
2answers
191 views
Alternating sum of binomial coefficients times logarithm
Trying to find a closed form expression for the following sum, or an asymptotic expression in terms of well known functions (like the Gamma function, for instance).
Let $m,n$ be positive integers ...
10
votes
1answer
409 views
Analogues of the Knuth and Forgotten equivalences on permutations: have they been studied?
Consider a totally ordered alphabet $A$ of $n$ letters. Let $W$ be the set of all words over $A$ which have no two letters equal. Then, for example, we can define the Knuth equivalence on $W$ as the ...
20
votes
1answer
649 views
A strange sum over bipartite graphs
While mucking around with some generating functions related to enumeration of regular bipartite graphs, I stumbled across the following cutie. I wonder if anyone has seen it before, and/or if anyone ...
2
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0answers
267 views
Software for Combinatorial Algebra sought
I am looking for software which helps me do straightforward tasks in combinatorial algebra. Let me give an example of what I mean by a straightforward task:
I have two graded (generally ...
8
votes
2answers
531 views
Ubiquitous Zimin words
Let $w$ be a word in letters $x_1,...,x_n$. A value of $w$ is any word of the form $w(u_1,...,u_n)$ where $u_1,...,u_n$ are words. For example, $abaaba$ is a value of $x^2$. A word $u$ is called ...
8
votes
1answer
585 views
Connected graded involutive bialgebras (Hopf algebras) sought (for Dynkin idempotent checking)
Again, there is a general and a concrete question:
Concrete question. Let $H$ be a connected graded bialgebra over a commutative ring $k$ with unity (where graded means $\mathbb N$-graded). Then, it ...
3
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6answers
233 views
Do stunted exponential series give projections of a cocommutative bialgebra on its coradical filtration?
Let $k$ be a field of characteristic $0$.
Let $H$ be a cocommutative connected filtered bialgebra over $k$. ("Connected" means that the counit, restricted to the $0$-th part of the filtration, is an ...
2
votes
1answer
275 views
Rational Binomial Identity
Can anyone give a reference, a proof, or a reference that explains why Maple can evaluate this identity mathematically correctly:
...
6
votes
1answer
232 views
Simplices in convex polytopes
This question is a direct generalization of:
Counting the (additive) decompositions of a quadratic, symmetric, empty-diagonal and constant-line matrix into permutation matrices
Given a convex ...
15
votes
2answers
1k views
Regular, Gorenstein and Cohen-Macaulay
All the statements below are considered over local rings, so by regular, I mean a regular local ring and so on;
It is well-known that every regular ring is Gorenstein and every Gorenstein ring is ...
3
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1answer
253 views
Monotonicity of complete homogeneous symmetric polynomials
The complete homogeneous symmetric polynomials are defined as
$$
h_k (x_1, \dots,x_n) = \sum_{1 \leq i_1 \leq i_2 \leq \cdots \leq i_k \leq n} x_{i_1} x_{i_2} \cdots x_{i_k}.
$$
For example,
$$
...
4
votes
1answer
275 views
On MacMahon's conjecture and a Schur function identity
Recently I am reading Professor Bressoud's book "Proofs and confirmations"。And chapter 4 of his book is about using Schur functions to prove Macmahon's conjecture on symmetric plane partitions: ...
12
votes
1answer
1k views
Sublattices of Young's Lattice
Young's Lattice is the lattice of inclusions of Young tableaux, or integer partitions.
In R. Stanley's Enumerative Combinatorics Vol. 1, Proposition 1.4.4., there is a generalization of integer ...
2
votes
1answer
196 views
Reference for: the Bruhat-minimal permutations not less than a fixed permutation pi?
Let $\pi\in S_n$. I recently needed to understand the permutations $\rho$ such that $\rho\not\leq\pi$ in Bruhat order. Since there are $O(n!)$ of those I really wanted a description of the $O(n^2)$ ...
6
votes
4answers
2k views
When is an algebra of commuting matrices (contained in one) generated by a single matrix?
Let C be an nxn matrix, then the polynomials in C (with appropriate coefficients) form an algebra of commuting matrices. I feel that I should know if the converse is true but I do not. So my first ...
4
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0answers
286 views
Can the Littlewood-Richardson cone be used for combinatorial optimization?
The Littlewood-Richardson cone $LR_{n, k}$ consists of all $k-$tuples $(a_1, a_2, \dots, a_k)$ of real $n-$vectors with monotonically decreasing entries such that there exist $k$ $n \times ...
6
votes
2answers
638 views
What is the most general “two in one row for A & in one column for B” theorem?
Let $A$ and $B$ be two Young tableaux, i. e. Young diagrams filled with the numbers $1$, $2$, ..., $n$ for some $n$ (not necessarily the same $n$). (They need not be semistandard.)
(a) (Etingof's ...
