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Coxeter matrix of Dyck path

I am trying to understand Gjergji Zaimi's answer in What are the periodic Dyck paths?. In the third paragraph he claims that Next, we define the matrix $X_D$ similarly to the Cartan matrix except we ...
AlgebraicPhantom's user avatar
-3 votes
0 answers
132 views

A presentation for the group $GL(n,\mathbb{Z}_p)$

Let $n\ge 2$. Let $p$ be a prime and $\mathbb{Z}_p$ denote the finite field with $p$ elements. I want to know about the presentation for the group $GL(n,\mathbb{Z}_p)$ consisting of its generators and ...
SPDR's user avatar
  • 103
4 votes
0 answers
98 views

Dimension of the intersection of the commuting variety with a particular subspace

Let $\mathcal C$ denote the commuting variety of pairs of matrices in $M_n(\mathbb{C})$, defined as: $$ \mathcal C = \{ (A, B) \in M_n(\mathbb{C})^2 \mid [A, B] = 0 \}. $$ It is well known that $\...
darko's user avatar
  • 309
7 votes
1 answer
487 views

Invertibility of a matrix defined using inner product

Let $n,m \geq 1$. We fix $n$ distinct vectors $x_1, ... , x_n \in \mathbb{R}^m$. We define $A \in \mathbb{R}^{n\times n}$ as \begin{equation} A_{ij} = x_i^T \left(n x_j - \sum_{1 \leq k \leq n} x_k \...
Goulifet's user avatar
  • 2,306
2 votes
0 answers
101 views

An inequality related to Problem 10210 AMM 1992 No. 3

Problem. Let $A$ be a $N \times N$ real matrix whose $(i,j)$ entry is $a_{ij} \ge 0, \forall i, j$. Let $1$ denote $N\times 1$ all-ones vector. Prove that $$N^2 1^\top A^\top A A^\top 1 \ge (1^\top A ...
River Li's user avatar
  • 1,053
0 votes
0 answers
45 views

Artinian simple algebras with involution

Let $A$ be an Artinian simple $K$-algebra with involution $*$. The algebra $A$ has a primitive idempotent $e$, and $D_e:=eAe$ is a division $K$-algebra due to Schur's lemma and the isomorphism $(eAe)^{...
khashayar's user avatar
  • 143
0 votes
0 answers
46 views

max eigenvalue and schatten-1 norm of depolarizing channel acting on trace-0 Hermitian matrix

Denote $\mathcal{H}^n$ as the $n-$dimension Hermitian matrices. Depolarizing channel $\Delta_p:\mathcal{H}^2\to\mathcal{H}^2$ is defined as $\Delta_p(A)=p\text{ tr }(A)~I/2+(1-p)A$ where $A\in \...
qmww987's user avatar
  • 91
2 votes
0 answers
126 views

A property of matrices formed by pairing of roots and coroots

Let $A$ be an $n\times n$ integral matrix, define its level $l(A)$ as $$l(A) := \begin{cases}0 &\det A = 0 \\ \text{smallest integer } N \text{ such that } NA^{-1} \text{ is integral} &\det A \...
pisco's user avatar
  • 528
2 votes
1 answer
153 views

On generation of $A_n$ by elements of prime order

There is a question regarding generation of finite simple groups with elements of prime order. Recently, Guralnick, Shareshian, Woodroofe and Teräväinen made advances in this direction. We have, for ...
Lucas's user avatar
  • 329
4 votes
1 answer
90 views

Tight upper bound on a ratio involving symmetric PSD matrices and Kronecker products

Let $\mathbf{A}_i \in \mathbb{R}^{d \times d}$ ($i = 1, \dots, T$) be symmetric positive semidefinite (PSD) matrices. Define the quantity $$ m = \frac{\lambda_{\max}\left(\sum_{i=1}^T \mathbf{A}_i^2\...
Ran's user avatar
  • 73
2 votes
1 answer
147 views

Baer sums of extensions

Apologies in advance if this question is too basic, I looked briefly through Weibel and the stacks project and couldn't find any relevant reference. Let $\mathcal{A}$ denote an abelian category, and ...
kindasorta's user avatar
  • 2,907
8 votes
1 answer
436 views

Function $\phi$ such that $f(\phi(x,y)) = f(x) + f(y)$

I have a continuous function $f:\mathbb{R}^n\to\mathbb{R}$, and I am looking for a continuous (or at least measurable) function $\phi:\mathbb{R}^{2n}\to\mathbb{R}^n$ such that $f(\phi(x,y))=f(x)+f(y)$....
gmvh's user avatar
  • 3,065
1 vote
1 answer
80 views

Hilbert symbol of a quaternion algebra given ramified places

I am reading the paper: https://projecteuclid.org/journals/experimental-mathematics/volume-17/issue-3/Derived-Arithmetic-Fuchsian-Groups-of-Genus-Two/em/1227121388.full in order to find an explicit ...
ah--'s user avatar
  • 155
3 votes
1 answer
114 views

Selmer complex and total complex

Thanks for your reading. I'm studying Selmer complex book by Jan Nekovar. For the definition of Selmer complex I meet a problem. In the introduction(page 9, 0.8.0) the author gives us a definition of ...
Rellw's user avatar
  • 319
13 votes
2 answers
1k views

What's the deal with De Morgan algebras and Kleene algebras?

The notion of Boolean algebras, and the corresponding classical propositional logic, is very standard, and it is easy to find information about them (for example, among many other such works, there is ...
Gro-Tsen's user avatar
  • 32.5k
6 votes
0 answers
102 views

Computer program for free restricted Lie polynomial

I am conducting numerical experiments involving the Gröbner–Shirshov Basis for restricted Lie algebras. At each step of the computation, I need to work with restricted Lie polynomials. Specifically, I ...
gualterio's user avatar
  • 1,013
3 votes
1 answer
103 views

References: rigorous algorithms for elementary computations in base-b with complexity estimates

Definitions/Notation: Fix positive integers $b$ and $M$. Consider the set of real numbers which can be exactly expressed with $2M+1$ coefficients in base $b$, defined by $$\mathcal{X}(b,M):=\{x\in \...
ABIM's user avatar
  • 5,405
47 votes
10 answers
6k views

Algebraic theorems with no known algebraic proofs

What are some good examples of algebraic theorems that have no known algebraic proofs? A few I know concern classifications of (not necessarily associative) division algebras over $\mathbb{R}$: the ...
4 votes
1 answer
171 views

Maximizing trace subject to two equality constraints

I am looking at the following optimization problem $$\begin{align} \underset{{\bf X}}{\text{maximize}} \qquad&\mathrm{tr}({\bf AX})\\ \text{subject to} \qquad& \mathrm{tr}({\bf X}) = 1,\\ &...
usergh's user avatar
  • 43
2 votes
0 answers
93 views

Free, easy-to-use program for noncommutative algebra over finite fields

I am looking for a computer program that can handle computations in noncommutative algebra over a finite field of prime order $p$. My requirements are: The program should be free, as I do not have ...
gualterio's user avatar
  • 1,013
4 votes
0 answers
167 views

How to prove the following equation (which involves binomials and determinant of 2×2 matrices)?

I have tried many ways to prove the following equation, such as the method of induction and expanding all the terms in the summation,but things got more complicated.I could not find an appropriate ...
tongjun's user avatar
  • 41
0 votes
0 answers
87 views

Is there a name for "applying linear operations to vector sequences from the right"?

Let $v_1,...,v_n\in\Bbb R^d$ be a sequence of vectors. When we say that we "linearly transform" this sequence, we mean that we apply a linear transformation $T\in\Bbb R^{d\times d}$ to each ...
M. Winter's user avatar
  • 13.6k
4 votes
1 answer
250 views

Connected Frobenius algebras non-semisimple as an object

A Frobenius algebra object $A$ in a tensor category $\mathcal C$ is said to be connected if $\text{Hom}_{\mathcal C}(\mathbb{1}, A)$ is a one dimensional vector space, where $\mathbb {1} $ denotes the ...
Mainak's user avatar
  • 43
4 votes
2 answers
365 views

Notion of prime congruences

We have the idea of a prime ideal in a commutative ring $R$ but in universal algebra, we generalize the notion of ideal to that of a congruence. I’ve thought over the question of what a prime ...
Lave Cave's user avatar
  • 293
1 vote
0 answers
153 views

Does it make sense to take a formal power series over a non-ring? [closed]

Suppose we have the set of nonnegative integers. This is obviously not a ring, and not even a group. But are we able to identify ring-like properties for it if we take a formal power series over it? ...
random's user avatar
  • 29
10 votes
2 answers
455 views

Is the number of similarity classes of integer matrices with given minimal and characteristic polynomial finite?

Latimer and MacDuffee proved that there is a bijection between similarity classes of integer matrices with irreducible characteristic polynomial $\chi$ and the ideal class monoid of $\mathbb{Z}[\alpha]...
Ben Marlin's user avatar
0 votes
0 answers
32 views

Right maximal ideals in skew-Laurent rings over division Rings

Let $R$ be a Noetherian domain, and let $D$ denote its division ring. Define $S = D_q[x_1^{\pm 1}, x_2^{\pm 1}]$ as an iterated skew-Laurent polynomial ring with the relation $x_1 x_2 = q x_2 x_1$. Is ...
Sky's user avatar
  • 923
0 votes
0 answers
92 views

Finitely generated module over a skew Laurent polynomial ring $\mathbb{K}[x_1^{\pm 1},x_2^{\pm1}]$

Let $A := \mathbb{K}_{\Lambda}[x_1^{\pm 1}, x_2^{\pm 1}, x_3^{\pm 1}, x_4^{\pm 1}]$, $B := \mathbb{K}_{\Lambda'}[x_1^{\pm 1}, x_2^{\pm 1}, x_3^{\pm 1}]$, and $C := \mathbb{K}_{\Lambda''}[x_1^{\pm 1}, ...
Sky's user avatar
  • 923
-1 votes
0 answers
21 views

Choosing between matrix normal and multivariate normal for Bayesian inference

I’m working on a Bayesian inference problem where I need to estimate a graph structure G with a spike-and-slab prior on each edge of G. My likelihood model is built on observed data R and covariance ...
JJbox's user avatar
  • 1
0 votes
0 answers
61 views

$\mathcal{R}$ is finite over $L_0[e,A]$

Let $\sigma:L \longrightarrow L$ an automorphism of infinite order, where $L_0 \subset L$ is its fixed field. Let $R$ be a commutative subring of $L\{\sigma\}$. Let \begin{equation} \mathcal{R}=\...
MChocko's user avatar
  • 69
1 vote
1 answer
109 views

Orbit spaces of n-tuples of square matrices under simultaneous conjugation

Let $n, p, \geq 1$ be integers. Denote the set of ordered partitions of $p$ by $\Pi$: each $\pi \in \Pi$ is an ordered $k$-tuple $(p_1,p_2, \dotsc, p_k)$ where $p_1+\dotsb+p_k = p$. Write $\pi \leq \...
Jon Elmer's user avatar
  • 185
4 votes
0 answers
131 views

Ring theoretical aspects of the DAHA

The double affine Hecke algebras (DAHA) were introduced by Cherednik in his study of Macdonald's inner product conjectures (which were solved affirmatively). Nowdays there are many variations of the ...
jg1896's user avatar
  • 3,318
6 votes
0 answers
139 views

Can an algebra be isomorphic to its own algebra of $n^2 \times n^2$ matrices but not its own algebra of $n \times n$ matrices?

Is there an associative unital algebra $A$ which is isomorphic to its own algebra of $n^2\times n^2$ matrices $\operatorname{Mat}_{n^2}(A)$, but not isomorphic to its algebra of $n \times n$ matrices $...
Theo Johnson-Freyd's user avatar
2 votes
0 answers
76 views

Does a matrix ring over a ring satisfy the Koethe conjecture if the coefficient ring itself satisfies the Koethe conjecture?

I just want to know whether the following statement is true or false. If $R$ is a ring satisfying the Koethe conjecture, then the matrix ring over $R$ also satisfies the Koethe conjecture. Or is it ...
Eunnaya First's user avatar
2 votes
0 answers
69 views

Link between Carathéodory's criterion and commutation in an orthomodular lattice?

In the theory of outer measures, Carathéodory's criterion constructs from an outer measure $\mu^*$ on $X$ a $\sigma$-algebra $\Sigma$ of subsets of $X$, on which the restriction of $\mu^*$ is a ...
Olius's user avatar
  • 193
9 votes
3 answers
1k views

Examples of combinatorial problems where the only known solutions, or most "natural" solutions, use representation theory?

In Solution of two difficult combinatorial problems with linear algebra, Robert Proctor presents two simply stated combinatorial problems, and gives solutions to them using a linear algebraic approach ...
4 votes
0 answers
211 views

When does a short exact sequence of abelian groups with $B\cong A\oplus C$ split?

$\hspace{20pt}$Duplicate on stackexchange. This question, in a way, extends this one. The question is what are some sufficient conditions on the abelian group $B$ so that if $B\cong A\oplus C$ and a ...
cnikbesku's user avatar
  • 171
0 votes
0 answers
57 views

Class of covariance matrices invariant under permutations

I am reading a paper on covariance matrix estimation, and in this paper is introduced a class of covariance matrices: \begin{equation} U(q, c_0(p),M)=\{\Sigma: \sigma_{ii}\leq M,\quad \max_j\sum_{j=1}^...
spenziak's user avatar
4 votes
1 answer
347 views

Do Frobenius subalgebras form a lattice?

A finite-dimensional, unital, associative algebra $A$ over a field $k$ is termed a Frobenius algebra if it is endowed with a nondegenerate bilinear form $\sigma : A \times A \to k$ satisfying the ...
Sebastien Palcoux's user avatar
5 votes
1 answer
539 views

Under what circumstances Is a symmetric matrix representable as a Coulomb matrix?

Question: I am exploring a neural network architecture inspired by physical interactions, where each neuron has associated "mass" and "position" vectors. The weight matrix between ...
mathoverflowUser's user avatar
5 votes
1 answer
178 views

Semisimplicity of algebras in fusion categories

Let $\mathcal{C}$ be a fusion category and $A \in \mathcal{C}$ be an algebra object. We say that $A$ is semisimple if its category of (right) modules $\mathsf{mod}_A(\mathcal{C})$ is a semisimple ...
AffSch's user avatar
  • 61
5 votes
0 answers
112 views

Finitely generated projective modules over Noetherian endomorphism ring

Let $\mathcal A$ be a locally Noetherian Grothendieck abelian category and $M\in \mathcal A$ be a Noetherian object. Set $B:=\text{End}_{\mathcal A}(M)$. Let $B$-mod be the category of finitely ...
Snake Eyes's user avatar
1 vote
0 answers
55 views

How computationally efficient are kernel tricks? [closed]

"If we compare to non-kernel polynomial regression it is O(Tnp) where is p is dimension of polynomial while kernel polynomial is O(n^2d) + O(T*n^2) where d is original number of attributes, ...
Saransh Gupta's user avatar
0 votes
0 answers
54 views

What properties do these "norm-equal" polynomials have?

Let us first define the "norm-equal" polynomials : For $f(x),g(x)\in \mathbb{C}[x]$, if $\forall z\in \mathbb{C},|z|=1$, we have $|f(z)|=|g(z)|$, then we call $f(x)$ and $g(x)$ are "...
aftermather's user avatar
1 vote
0 answers
92 views

Proposition 6.2.7 from Goss

I'm following David Goss's book Basic structures of function field arithmetic. Let $L$ be an extension field of $L_0$ and $\sigma$ an automorphism of infinite order which fixes $L_0$. Let $L\{\sigma\}$...
MChocko's user avatar
  • 69
0 votes
0 answers
104 views

Non-degenerate bilinear pairing of finite dimensional algebras

A finite dimensional algebra (over $\mathbb{C}$, say) is said to be Frobenius if it comes equipped with a nondegenerate bilinear pairing \begin{align*} \langle -, - \rangle : A \times A \rightarrow \...
James Steele's user avatar
2 votes
1 answer
198 views

Maximal sub-$\mathbb{C}$-algebras of $\mathbb{C}[x,y]$

After asking this question and finding this relevant paper, I would like to ask the following question: For every $a,b \in \mathbb{C}$, denote: $A_{a,b}=\mathbb{C}[(x-a)(x-b),x(x-a)(x-b),y]$ and $B_{a,...
user237522's user avatar
  • 2,837
6 votes
3 answers
490 views

Boolean rings with many automorphisms

Does there exist an infinite Boolean ring $R$ (not assume unital, only associative) with the property that for any nonzero $x,y\in R$, there is a ring automorphism $\varphi\colon R\to R$ such that $\...
Greg Oman's user avatar
  • 131
2 votes
0 answers
67 views

Preserving invertibility with adding rows

Suppose I have two $m\times n$ matrices $A$ and $B$ such that an $m\times m$ submatrix of $A$ is invertible if and only if the corresponding $m \times m$ submatrix of $B$ is. Now let's say I append a ...
Kevin S.'s user avatar
4 votes
1 answer
239 views

True or false? Every left or right cancellative, duo semigroup is cancellative

A semigroup $S$ is duo if $aS = Sa$ for all $a \in S$, where $aS := \{ax: x \in S\}$ and similarly for $Sa$; for instance, every commutative semigroup is duo, and so is every group. On the other hand, ...
Salvo Tringali's user avatar

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