0
votes
0answers
43 views
Big eigenvalues of a special stochastic matrix
Given a matrix $M$ of size $n\times n,$ we write its different eigenvalues by $x_1,x_2,\ldots,x_m$ with $m\leq n$ such that $|x_1|>|x_2|>|x_3|>\cdots|x_m|,$ and call $x_2\doteq |\l …
0
votes
0answers
57 views
can I find the rotation matrix R and translation matrix T from 3x3 matrix?
In the pinhole camera model, I can get the homography 3x3 matrix of two images.
My problems is: provided an camera intrinsic matrix(the projection matrix), can I find the find the …
6
votes
1answer
167 views
Inverse of a totally unimodular matrix
A unimodular matrix $M$ is a square integer matrix having determinant $+1$ or $−1$.
A totally unimodular matrix (TU matrix) is a matrix for which every square non-singular submatr …
2
votes
1answer
73 views
Maximizing supermodular functions
I have a real supermodular objective function which I want to maximize with constraint. The constraint is on the size, like |A|=k .
I am wondering if anyone can give me more inf …
1
vote
1answer
126 views
Finding a point farthest away from $k$ points in a polygon
There are $k$ points placed inside a polygon and I am interested in finding a point inside the polygon (not necessarily on its boundary) who's minimum distance to any of the $k$ po …
8
votes
3answers
511 views
Is the tensor product of polyhedra a polyhedron?
Conventions: A polytope in a finite-dimensional $\mathbb R$-vector space $V$ is defined to be a convex hull of finitely many points in $V$. A polyhedron in a finite-dimensional $\m …
0
votes
1answer
202 views
Schur complement and negative definite matrices
Hello,
My question regards to the Schur complement lemma. Consider the matrix $M=\left( \begin{array}{cc}
A & B\\
B^T & C \end{array}\right)
$.
According to the lemma $M\ …
0
votes
0answers
94 views
Sum of piecewise linear functions
I have a problem minimizing sum of piecewise linear functions. Given $f:R\rightarrow R$ with $f(x) = \sum_{i=1}^n \max (a_ix,b_ix+c_i)$ and $a_i,c_i <0; b_i>0$ find an equation …
0
votes
0answers
155 views
Gradient Descent for Primal Kernel SVM with Soft-Margin(Hinge) Loss
Given the primal objective
$$F({\bf a})=L\sum_{i,j}a_{i}a_{j}k(x_i,x_j) + \sum_{i}max(0, 1-y_i \sum_{j}a_jk(x_i,x_j)$$
for the soft margin SVM, where ${\bf a}=(a_1,...,a_N)$, N be …
0
votes
1answer
188 views
Finding linearly independent columns of a large sparse rectangular matrix
I have a problem that necessitates solving a large non-negative least-squares
problem. My matrix A is large, sparse, highly rectangular (num rows >> num cols)
and nearly binary. …
1
vote
0answers
76 views
Matrix Minimax problem
I have the equation $\Sigma_k(M_k{p_k})V=EV$, where the $M_k$ are n*n real Hermitian matrices, $V$ is a n*n eigenvector matrix, $E$ a dim-n energy eigenvector and the $p_k$ scalar …
0
votes
1answer
157 views
Nonstandard Hessian approximations in Gauss-Newton
The Gauss-Newton algorithm optimizes functions
$$
E(x) = \sum f(x)^2
$$
by approximating f as (locally) linear, in which case the Hessian of $E$ is approximated as
$$
H = 2 \sum …
3
votes
2answers
125 views
Bounding the minimal maximum norm of a solution of a linear system.
I would be grateful for pointing me out a reference to some general bound on the $\ell_{\infty}$ norm of a solution of a linear system. To be specific, suppose that we have an unde …
1
vote
1answer
111 views
Results for minimizing the norm w.r.t a unitary matrix
Suppose $x \in \mathbb{R}^n$, $B,U \in \mathbb{R}^n\times\mathbb{R}^n$ and $U$ a unitary matrix. Define $g_{U}(x) = || BUx||$ where $||.||$ is some norm or norm-ish function on $\ …
2
votes
2answers
420 views
Dual Norm For Sum of 2-Norms
What is the dual of a norm that is the sum of two-norms? Specifically, say we have the following norm for $\mathbf{x}\in \mathbb{R}^n$ and $\mathbf{A}_i \in \mathbb{R}^{m \times n} …

