Questions tagged [algebraic-combinatorics]
For problems involving algebraic methods in combinatorics (especially group theory and representation theory) as well as combinatorial methods in abstract algebra.
264
questions
0
votes
1
answer
34
views
Exercise 9.6 in Algebraic Combinatorics by Stanley
Exercise 6 in chapter 9 of Algebraic Combinatorics by Stanley: Let $G$ be a finite graph on $p$ vertices with Laplacian matrix $L(G)$. Let $G'$ be obtained from $G$ by adding a new vertex $v$ and ...
2
votes
1
answer
51
views
Regarding the number of variables in Symmetric Functions
I'm studying Symmetric Functions and I came across a doubt that could be considered stupid but I need clarifications.
In the course I'm following we introduced symmetric functions as formal series of ...
4
votes
1
answer
56
views
Exercise 8.6 of Algebraic Combinatorics by Stanley
Problem 6 in Chapter 8 of Algebraic Combinatorics by Stanley: Show that the total number of standard Young tableaux (SYT) with $n$ entries and at most two rows is ${n \choose \lfloor n/2 \rfloor}$. ...
1
vote
1
answer
37
views
Exercise 7.2 in Algebraic Combinatorics by Stanley
This is exercise 2 in chapter 7 of Algebraic Combinatorics by Stanley.
For part (a), I first found the entire automorphism group. By labeling the root 1, and then numbering off the remaining vertices ...
1
vote
0
answers
34
views
Exercise 3.1 of Algebraic Combinatorics by Richard Stanley
Exercise 3.1: Let $G$ be a (finite) graph with vertices $v_1, \ldots, v_p$. Assume that some power of the probability matrix $M(G)$ defined by $(3.1)$ has positive entries. (It's not hard to see that ...
0
votes
0
answers
116
views
find the general solution the recurrence equation $b_n = 3b_{n-1} - b_{n-3}$
here are the steps I have done to try and find the general solution of this relation:
$$ b_n = 3b_{n-1} - b_{n-3}\\ = b^n = 3b^{n-1} - b^{n-3}$$
then divide by $b^{n-3}$ to get $$b^3 = 3b^2 - 1$$
then ...
- 15
1
vote
1
answer
44
views
find the number of ways to distribute 30 students into 6 classes where there is max 6 students per classroom
here is the full question:
Use inclusion/exclusion to find the number of ways of distributing 30
students into six classrooms assuming that each classroom has a maximum capacity
of six students.
Let $...
- 15
1
vote
2
answers
78
views
Identity of Schur polynomials
Let $p_n$ be the power sum symmetric polynomial,
$$p_n=x_1^n+x_2^n+\dots x_n^n$$
in $n$ variables, and let $s_\lambda$ be the Schur polynomials. I am new to Schur polynomials so I'm not sure what ...
- 83
0
votes
1
answer
35
views
create a recurrence relation for the number of ways of creating an n-length sequence with a, b, and c where "cab" is only at the beginning
This is similar to a problem called forbidden sequence where you must find a recurrence relation for the number of ways of creating an n-length sequence using 0, 1, and 2 without the occurrence of the ...
- 15
0
votes
0
answers
14
views
Isometric automorphisms of the ring of symmetric functions
I was trying to understand how special the $\omega$ involution on the ring of symmetric functions $\Lambda$ or $\Lambda^n$ (restriction to $n$ variables, just in case if by some magic, the situation ...
- 143
1
vote
0
answers
16
views
Composition of homomorphisms of association schemes
In Zieschang's "Theory of Association Schemes", in section 5.2, he remarks that the composition of homomorphisms is not always a homomorphism. I've been struggling to find an example of that ...
- 235
2
votes
0
answers
77
views
Restriction of induced representation over a Young subgroup and Littlewood-Richardson coefficients
I'm inexperienced in the representation theory of the symmetric group, so please correct my possible mistakes. Fix $m\leq n$, $G:=S_n$ and $H:=S_m\times S_{n-m}$ as a Young subgroup of $G$. Let $V^{\...
- 4,886
0
votes
0
answers
23
views
Affiness, $U_{2,4}$ and $M(K_4).$
I do not know why $M(K_4)$ is not affine over $GF(2)$ or $GF(3)$ but it is affine over all fields with more than 3 elements. I proved that $U_{2,4}$ is $\mathbb F$-representable iff $|\mathbb F| \geq ...
- 3,181
0
votes
0
answers
20
views
Lift and frame matroids.
I want to read more about lift matroid and frame matroid and their flats and relations to signed graphs, do you know any basic resources for this?
- 2,087
1
vote
0
answers
23
views
Characteristic polynomial and bounded regions.
I know that the number of bounded regions of a homogeneous hyperplane arrangement $\mathcal{A}$(a collection of n hyperplanes) in $\mathbb R^d$is ${ n - 1 \choose d}$ but how can this be expressed in ...
- 3,181