All Questions
Tagged with co.combinatorics reference-request
335 questions with no upvoted or accepted answers
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The semicat of morphisms which are neither right nor left invertible
Given a cat $\bf C$, the class $\mathcal{S}$ of all $\mathbf{C}$-morphisms that are neither left nor right invertible, generates a "genuine" subsemicat $\bf S$ of $\bf C$ (if necessary, see here for ...
- 10.5k
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168
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What is known about infinite diminished disjunctive compounds of loopfree partizan combinatorial games?
Background
Basic theories of loopy (normal-play) games which may go on forever under the usual disjunctive sum (the game ends when there are no moves available for you in any component on your turn) ...
- 613
1
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193
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Lattice-point enumeration question involving linear combinations of matrices
I would like to know some references to learn more about an answer to this question, if there are any references:
Let $A_1, \dots , A_m$ and $B$ be $n\times n$ symmetric matrices. Let $$S = \{(x_1, \...
- 170
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229
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Counting equivalence classes in the transitive closure of two equivalence relations
Let $X$ be a finite set, and let $P_i$ and $Q_j$ be two partitions of $X$:
$$\bigsqcup_i P_i = \bigsqcup_j Q_j = X.$$
The finest partition which is nevertheless coarser than both $P$ and $Q$ is ...
- 5,898
1
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0
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388
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Has anyone seen this version of ring toss (combinatorial object) before?
In reference to a
question on work of Westzynthius and another
question relating to Jacobsthal's function, I have formed a game which I immodestly call Paseman's Ring Toss. I hope that it has been ...
- 13k
1
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260
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Looking for paper "The cyclotomic identity" by Metropolis and Rota
I am looking for a copy of the paper in the title, appeared in the proceedings
"Combinatorics and algebra (Boulder 1983), Contemp. Math., 34"
and reprinted in
"Gian-Carlo Rota on Combinatorics, ...
- 4,482
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137
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State of the art on attempts to solve the elliptic curve discrete logarithm problem through transfering the problem to a weaker curve
Let an elliptic curve $E$, and 2 points on such curve $P$ and $O$ the methods I’m talking about consist in creating a weaker elliptic curve $F$ and mapping $P$ and $O$ to $F$ while successfully ...
- 87
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52
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Reference request for the determinant of a matrix constructed from Pascal's triangle
One can prove by induction that the matrix $M^{(n)}$ given by
$$ \begin{pmatrix}
1 & 1 & 1 & 1 & \dots & \binom{n}{0} \\
1 & 2 & 3 & 4 & \dots & \binom{n+1}{1} \...
- 5,546
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0
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117
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An interesting identity involving skew-Schur functions
Denote $\rho=(-\frac12,-\frac32,-\frac52,\dots)$. I was reading this interesting paper, where in particular, the authors claim that one can get the expression in (2.9)
\begin{align*}
\prod_{k\geq1}(1+...
- 43.2k
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57
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Reference for packing property and König property
Can someone please suggest reference material to study about the packing property and König property of ideals and some examples?
- 21
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217
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On characters of the symmetric group: Part 2
This question is related to my earlier MO quest.
For an integer partition $\lambda$, denote $\ell(\lambda)=$ length, $\vert\lambda\vert=$ size and $\lambda=$ conjugate of $\lambda$. Allow to write $\...
- 43.2k
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55
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Modeling player interactions in multi-dimensional rating systems
In traditional rating systems (such as Elo), a player's strength is represented by a single scalar value, which is assumed to be consistent across different opponents. However, in some games, the ...
- 1
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What should we call the area for which the lower border is a Motzkin path?
We can draw a Motzkin path from $(0,0)$ to $(n/2,n/2)$ using steps $(0,1)$, $(1,0)$ and $(1/2,1/2)$, such that the path never goes below the line $y=x$. Consider the area bounded by the Motzkin path, ...
- 135
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86
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Real world application of large sets like syndetic sets, central sets
Large sets in $\mathbb{N}$ have strong combinatorial structures. For example, it is known that central sets in $\mathbb{N}$ contain arbitrarily long arithmetic progressions. It also contains solutions ...
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109
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Applications of Jack polynomials
I developed four libraries (Julia, R, Python, Haskell) for the computation of Jack polynomials. I developed them for fun because I found this was programmatically interesting. But now I'd like them to ...
- 2,560
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84
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Bounds for smallest non-trivial designs
Given $s>t\ge 2$, let $N(s,t)$ be the smallest integer $n>s$ such that there exists an “$(n;s;t;1)$-design” (i.e., a collection of $s$-subsets $e_1,\dots,e_m$ of $[n]:=\{1,\dots,n\}$, such that ...
- 3,499
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145
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Bound on solutions of $Ax \ge b$
Let $A \in \mathbb{Z}^{m \times n}, b \in \mathbb{Z}^{m \times 1}$.
One can show that if there is a solution of $Ax \ge b, x \in \mathbb{R}^n$ then there is one such that $\|x\|_{\infty} \le c (\|A\|_{...
- 439
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55
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Comparing spectral radius of two graphs using the entry of Perron vector
Suppose we have a graph $G$.
Let $A$ be the adjacency matrix of $G$ and $x$ be the corresponding Perron vector.
Let $x = (x_1,x_2,\cdots,x_n)^t$, where $x_i$ corresponds to the vertex $i \in V(G)$.
We ...
- 199
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120
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Does an extension of the B.E.S.T. theorem for multiple Eulerian circuits exist?
Given a directed multigraph $G=(V,E)$ (multiple edges and loops are permitted) the number of distinct Eulerian circuits for $G$ can be calculated with the B.E.S.T. theorem. Does a similar theory for ...
- 1,295
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75
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Objects equinumerous with $3$-ary partitions?
There is a concept of the so-called RP-compositions of an integer discussed by K. Q. Ji and H. S. Wilf in Extreme palindromes. They proved the following result too:
Theorem. The number of RP-...
- 43.2k
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171
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Total sum of characters over partitions with distinct parts
In my earlier quest, we looked at $\chi_{\mu}^{\lambda}=$value of an irreducible character of the symmetric group $\frak{S}_n$, where $\mu$ and $\lambda$ are (unrestricted) partitions of $n$. Then, ...
- 43.2k
0
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0
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87
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Reference request for additive persistence of a number
It is well known fact that each natural number can be represented uniquely in any base. So we can define digit sum function whose value is sum of digits of the natural number in given base.
Let $f(n,b)...
- 249
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142
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Counting special paths on a certain rectangle integer grid (binary matrix)
Crossposting from MSE after getting no answers. The bounty on the MSE question is still open, but not for long. Be advised that the comments of the MSE question regard an obsolete version, and that ...
- 149
0
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0
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186
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Generalization of elementary symmetric polynomials
The elementary symmetric polynomials (ESPs) are defined as -
\begin{align*}
E_{1}^{1}
&= X_1,
\\
E_{1}^{2}
&= X_1 + X_2,
\\
E_{2}^{2}
&= X_1 X_2,
\\
E_{2}^{3}
&= X_1 X_2 + X_1 X_3 + ...
- 47
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0
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30
views
Maximum nonintersecting interval pick
This surely has been solved in the context of scheduling already! (Shall I ask on some computer SE instead?)
Assume we have a set of closed "intervals" on $\mathbb Z$ ($\mathbb R$ isn't ...
- 4,829
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135
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Reference for discrete Laplacian on $\mathbb{Z}$
For $x\in \mathbb{R}^\mathbb{Z}$, let the discrete Laplacian be defined as
\begin{align*}
(\Delta x)_k = 2x_k-x_{k+1}-x_{k-1}.
\end{align*}
I am looking for good references about its spectrum (or ...
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87
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Necessary Conditions for a Graph not possible to Rainbow Color?
Suppose we have a $t$-uniform hypergraph ($t \ge 3$) $G$, and have $t$ colors available. A question in my research is equivalent to asking what the necessary and sufficient conditions are on $G$ for ...
- 103
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0
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167
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Negative $q$-binomial series: reference request
There seems to be a result for formal series (I hope this is right) for all integer $r\ge 0$
$$
\sum_{n\ge 0} (-x)^n\ {{n+r}\choose{r}}_{q} = (1+x)^{-1}(1+qx)^{-1}\dots
(1+q^{r}x)^{-1}
$$
where the $q$...
- 1,143
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266
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Completing a dyadic sum
Suppose I knew the behaviour of a given sum in every other interval, for example:
$$
\sum_{\substack{0\leq a \leq x\\ a\equiv 1 (k)}} \sum_{x/(a+k/2)< b \leq x/a} f(b) \sim g(x),
$$
for any $x>1$...
- 3,799
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131
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terminology: monotone maps of posets such that the image of a lower set is a lower set
How are called in combinatorics
monotone maps of partially ordered sets such that the image of a lower set is a lower set, i.e. closed (or open) maps of finite topologies? Is there a classification ...
- 113
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105
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Counting path generating sentences in a specific formal language
Given a formal grammar of a language or an Turing machine of the language, can we count the path that generating sentences of the language?
For example, we know that if the grammar is context-free ...
- 3,094
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0
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141
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Reference Request: a paper by Yoseloff about a proof of Sperner's Lemma
Dear Overflow,
Apologies in advance if I'm posting this in the bad place, but I was hoping some of you could point out to me a place where I could read online the following paper by Yoseloff, where ...
- 625
0
votes
0
answers
71
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products/factoring of two hypergraphs with same vertex set?
all the basic products for graphs have been extended to hypergraphs[1].
is there a concept of a product of hypergraphs with the same vertex set? has this been studied?
normally the hypergraph ...
- 529
0
votes
1
answer
349
views
Log associahedra and log noncrossing partitions--raising ops and symmetric function theory for $A_n$ (references)
Where do the following three sets $[LA]$, $[ILA]$, and $[LN]$ of partition polynomials appear in the literature?
There are two sets of partition polynomials, not in the OEIS, that serve as the ...
- 10.5k
-1
votes
1
answer
105
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What type of graph is this? (Edges that are valid / invalid depending on route to node)
I'm trying to model a questionnaire where the flow between questions depends on the answers given in previous questions.
Example. (Node represent questions, edges represent answers).
As you can see ...
- 1