All Questions
2,026 questions with no upvoted or accepted answers
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Expressing a polynomal as products of shifted Riemann zeta functions and reciprocals.
Suppose I have a polynomial $f$ in $p,t,$ say $f=1 \pm p^{a_1}t^{b_1} \pm \cdots \pm p^{a_s}t^{b_s}$ with $a_i,b_i \in \mathbb{N}\cup0$ and $b_i$ is non-zero. Let $X:=${$ \ (1-p^it^j) | i,j \in \...
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186
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Ring of Integers as subring with most irreducibles
Let $L$ be a number field. Is it possible to define its ring of integers $R$ by saying it's the subring with (in a fuzzy sense) the "most" irreducibles?
user11863
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98
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Is the inverse operation on an ordered division ring continuous?
Let $R\hspace{.005 in}$ be a division ring. $\;\;$ Let $\:\leq\:$ be a total order on $R\hspace{.005 in}$ such that for all elements $x,y,z$ of $R$ :
if $\: x\leq y \:$ then $\:\: x+z\:\leq\:y+z \:\:$...
user5810
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157
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Matrices satisfying certain pair-wise constraints
Consider given pairs of variables: $a_{ir1},a_{ir2}\in \mathbb{R}^{m \times m}$ and $a_{jr1},a_{jr2}\in \mathbb{R}^{m \times m}$, where $r \in \{1,2,\cdots,t\}$, consider the constraints:
$\sum_{r=1}^...
- 13.9k
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241
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Does regularity of a D-module for an unusual filtration imply regularity for the usual one?
One definition of regular D-modules on affine space is that a D-module is regular if it has a filtration compatible with the order filtration on differential operators whose associated graded is ...
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185
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Why does the OLS estimator simplify as follows for the single regressor case?
I was reading in "A Guide to Econometrics" that given $Y = X \beta + \epsilon$, the variance covariance matrix of $\beta^\text{OLS}$ is given by $\sigma^2 (X' X)^{-1}$ where $\sigma^2$ is the variance ...
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Eigenvalues of anti-circulant matrices
Is there any theorem to find the eigenvalues of any anti-circulant matrix using the equivalent (with the same first row) circulant matrix. I found out that,
for any anti-circulant matrix, the ...
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148
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Bogus(?) proof for equivalence of normal and dual distributivity conditions in lattices
I am attempting to prove the equivalence of the following two definitions of distributive lattices:
$(a \lor b) \land c = (a \land c) \lor (b \land c)$
$(a \land b) \lor c = (a \lor c) \land (b \lor ...
- 101
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168
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Working in a ring with something similar to elliptic curve factorization?
Elliptic curve factorization tries to factor integer $n=pq$ by working on an elliptic curve $E(\mathbb{Z}/n\mathbb{Z})$ and for a point $P$ computes $Q=kP , k \in \mathbb{N}$ hoping to find the point ...
- 454
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177
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Exotic isomorphism of matrix rings (2)
Let $R,S,T$ be (associative, with a 1) rings, and $m,n,r,s$ be non-negative integers.
If
(a) $R$ is isomorphic to $M_{m\times m}(T)$ and $S$ is isomorphic to $M_{n\times n}(T)$ and $m\cdot r = n\...
user5810
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667
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Looking for product of symmetric polynomials evaluated at roots of unity
Consider $a_{1} = \alpha^{N-n}, a_{2} = \alpha^{N-n+1}, a_{3} = \alpha^{N-n+2}, a_{4} = \alpha^{N-n+3}, \cdots, a_{n} = \alpha^{N-1}$ where $\alpha$ is a complex $N$th root of unity where $N = 2 + (n-...
- 13.9k
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289
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Good and/or standard notation for the abelianization of a Lie algebra
I'd like to solicit good notations for the abelianization of a Lie algebra $\mathfrak g$. One could write $\mathfrak g/[\mathfrak g,\mathfrak g]$, or even $H_1(\mathfrak g)$ but I'd like something ...
- 4,898
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306
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A finite direct product of Azumaya algebras may not be Azumaya?
Looking for an example, if it exists, of a finite set of Azumaya algebras $A_i$ such that $\oplus A_i$ is not Azumaya.
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206
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Vector-valued valuations on lattices
There's a fair amount of work on valuations on (modular) lattices, by which I mean functions $v : \mathcal{L} \rightarrow R$ that satisfy the modular expression
$$v(x) + v(y) = v(x \wedge y) + v(x \...
- 4,462
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199
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Intersection between a line and an n-dimensional parallelotope
Suppose that I have a line in an $n$-dimensional space described by
$$ X=A+Bk, \quad \quad X,A,B \in \mathbb{R}^n, k \in \mathbb{R} $$
here $A$ is known and I want to find all the possible vectors $B$ ...
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answer
257
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How to find $K,W,S$ in the Mostow decomposition theorem?
The Mostow decomposition theorem states:
Let $Z$ a nonsingular complex matrix, then $Z$ can be factored as:
$$Z=We^{iK}e^S$$ where: $W$ is unitary, $K$ is real and skew symmetric and $S$ is real and ...
- 399
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268
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Nonnegative Matrix
Let $A=E+\sqrt{-1}B$, where $E=diag\{0,1,\cdots,1\}$, $B$ is a real symmetric matrix. Let $A^*$ denote the adjoint matrix of $A$, i.e. $AA^*=\det A\cdot I$. I hope the real part of adjoint matrix ${\...
- 303
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180
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(probably simple) optimization question
Suppose you have a concave function defined over a non-polyhedral convex cone and you are interested in the infimum. What would be standard approaches to tackle the question? (The cone is actually PSD ...
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Choosing between matrix normal and multivariate normal for Bayesian inference
I’m working on a Bayesian inference problem where I need to estimate a graph structure G with a spike-and-slab prior on each edge of G. My likelihood model is built on observed data R and covariance ...
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1
answer
199
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Isomorphism between subgroups by preserving index
Let $C$ be a subgroup of a group $A$ such that $C\cong A/\{\pm1\}$ and $D$ be a subgroup of $B$ such that $D\cong B/\{\pm1\}$. Let $\pi:A\to B$ be a group homomorphism, and let $\pi$ induce a ...
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1
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293
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spectrum of a special class of tridiagonal matrices
Consider a real and symmetric tridiagonal matrix with zero diagonals and where subdiagonals and superdiagonals are equal to 1 except the (1,2)-th component being equal to $a$, i.e.,
$$\begin{bmatrix}...
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-1
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1
answer
492
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Upper bound on iterations count for power iteration algorithm
I'm stuck trying to get upper bound on iterations count for power iteration algroithm for finding first eigenvalue of adjacency matrix $A$ given tolerance value. I've tried to figure something out ...
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1
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445
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What is wrong with the argument that zero permanent is polynomial?
This Lecture summarizes some well known facts about $\#P$ completeness of permanent.
Given a CNF formula $\phi$ on $n$ variables, they construct
matrix $A$ such that:
$$perm(A)=4^{3m} \#SAT(\phi)$$
...
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-2
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1
answer
183
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Property of positive semi-definite
Let $A$ is a positive semi-definite matrix like this:
$$ A = \begin{bmatrix}
1 & \alpha_{1,2} & \alpha_{1,3} & \alpha_{1,4}\\
\alpha_{1,2} & 1 & \alpha_{2,3} & \alpha_{2,4}\\
\...
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113
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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 ...
- 103
-3
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1
answer
270
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Relationship of eigenvalue/eigenvector of hermitian matrix R and QRQ (Q is diagonal)
For a hermitian matrix R and a diagonal one Q, is there any relationship between eigenvalues/eigenvectors of R and QRQ?
To be specific, assuming the eigenvalue decomposition of R is R=VDV*, then can ...
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