Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 1898

The study of the properties of real and complex matrices that are more close to analysis and operator theory. For instance: the properties of positive definite matrices, matrix inequalities, perturbation analysis, matrix functions, inequalities between eigenvectors and singular values, majorization.

3 votes
Accepted

Algorithm for Computing Kronecker's Canonical Form for Matrix Pencils

GUPTRI by Jim Demmel and Bo Kagstrom computes a triangular decomposition that reveals the Kronecker structure of a pencil. It is Fortran code that can be called from Matlab using a Mex-file interface. …
Federico Poloni's user avatar
8 votes
Accepted

How to solve a non-homogeneous quadratic matrix equation?

(commenting about the equation with the plus sign, I hope that the correction was right). This is one of the few quadratic matrix equations that have a closed form solution. Set $A=-H^{-1}$; then $G …
Federico Poloni's user avatar
2 votes

The eigenvectors and eigenvalues of matrix geometric mean

As for visualization, I have seen SPD 2x2 matrices represented as ellipsoids (such as this one, which would be a 3D case), and the segment joining $A$ and $B$ in that Riemannian distance as a sequence …
Federico Poloni's user avatar
2 votes

How could I extend this result to a case where the matrices were not of full rank?

The natural way to relax the condition $A \geq XB^{-1}X^*$ to the case when $B$ is not full-rank is transforming it to $$ \begin{bmatrix} A & X\\ X^* & B \end{bmatrix} \geq 0, $$ which is equivalent b …
Federico Poloni's user avatar
8 votes

About Sylvester's determinant

The common ground of those two formulas is related to the Woodbury matrix identity. This relation is a useful statement that shows what happens to the inverse when one "updates" a matrix $A\in\mathbb{ …
Federico Poloni's user avatar
14 votes
Accepted

Are Diagonally dominant Tridiagonal matrices diagonalizable?

Counterexample: $$ \begin{bmatrix} -1 & 1 & 0 & 0\\ 0 & -1 & 1 & 0\\ 0 & 0 & -2 & 2\\ 0 & 0 & 2 & -2 \end{bmatrix} $$ is defective: its eigenvalues are $-1,-1, 0, -4$ (it is block triangular, so its …
Federico Poloni's user avatar
1 vote

Matrix Generator for M/M/1 Queue Waiting Time Distribution

Almost. The generator is ${\bf Q} =\left( \begin{array}{ccccc} -\lambda & \lambda & 0 & 0 & 0\\ \mu & -(\lambda+\mu) & \lambda & 0 & 0\\ 0 & \mu & -(\lambda+\mu) & \lambda & 0 \\ 0 & 0 …
Federico Poloni's user avatar
11 votes
Accepted

When the sum of positive definite matrices converges, does the sum of the norm of the associ...

You can bound $\|A_k\| \leq C(n)\max_{i,j} |(A_k)_{ij}|$ for some function of the dimension only $C(n)$, because all norms are equivalent in finite dimension. If I am not mistaken $C(n)=\sqrt{n}$, but …
Federico Poloni's user avatar
2 votes

Woodbury formula

Since there are only few answers, I'll add a shameless plug and advertise one of my papers. Basically, we first used SMW as a computational tool to speed up a matrix inversion, and then we found out …
Federico Poloni's user avatar
1 vote
Accepted

SVD of two matrices A and B having the same right singular vectors?

Those notes do not refer to the "usual" SVD, but to the generalized SVD, which is a different decomposition of a pair of matrices (and does not require $X$ to be orthogonal, in particular). For a qui …
Federico Poloni's user avatar
2 votes
Accepted

Reference request: continuity of Cholesky factor

A subtle issue is that $\Pi$ is not unique here. For instance, if $$ A = \begin{bmatrix} 1 & 0 & 0\\\\ 0 & 0 & 0\\\\ 0 & 0 & 0 \end{bmatrix} $$ then you can take both the identity and $(23)$ as the …
Federico Poloni's user avatar
3 votes

How do you solve this quadratic matrix equation?

This question is not an exact duplicate, but my answer gives you a pointer that applies also to your case.
Federico Poloni's user avatar
2 votes

Singularity of matrix pencil-like expression

The statement is false. Take $3\times 3$ matrices such that $A_{11}=B_{22}=1$ and all other entries are zero. Then $EA-hB$ has the third column equal to $0$, but the row spaces of $A$ and $B$ are disj …
Federico Poloni's user avatar
0 votes

Generate a low-rank sparse covariance matrix

Matlab's sprandsym generates a random sparse positive-definite matrix by starting from a diagonal matrix and applying to it Jacobi rotations, i.e., rotation matrices that act only on two components. I …
Federico Poloni's user avatar
4 votes

What are interesting heuristics of determining how far given matrix is from a singular one?

Another interesting concept in this direction is the pseudospectrum. (sorry for the one-line answer).
Federico Poloni's user avatar

15 30 50 per page