# Matrix Definition and 121 Discussions

The Multistate Anti-Terrorism Information Exchange Program, also known by the acronym MATRIX, was a U.S. federally funded data mining system originally developed for the Florida Department of Law Enforcement described as a tool to identify terrorist subjects.
The system was reported to analyze government and commercial databases to find associations between suspects or to discover locations of or completely new "suspects". The database and technologies used in the system were housed by Seisint, a Florida-based company since acquired by Lexis Nexis.
The Matrix program was shut down in June 2005 after federal funding was cut in the wake of public concerns over privacy and state surveillance.

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1. ### The Cooper pair box Hamiltonian in the matrix form

Hello, In my problem I need to We are advised to create the Cooper pair box Hamiltonian in a matrix form in the charge basis for charge states from 0 to 5. Here is the Hamiltonian we are given H=E_C(n-n_g)^2 \left|n\right\rangle\left\langle...
2. ### What is the necessary condition for matrix commutation?

Hi all! I was wondering what the necessary condition is for two arbitrary matrices, say A and B, to commute: AB = BA. I know of several sufficient conditions (e.g. that A, B be diagonal, that they are symmetric and their product is symmetric etc), but I can't think of a necessary one. Thanks...
3. ### Direction cosine matrix of rolling disk on circular ring

Hey all, I'm stuck on this problem and not sure how to proceed/if I'm in the right direction. Problem: One reference frame N sits at the origin (inertial frame) while another frame, B, describes a disk rolling on a circular ring about the other frame. Picture below (A) find the direction...
4. ### Relation between image(A) and image(A^2+A)

Homework Statement What is the relation between the image of A and the image of A2 + A? Homework Equations The Attempt at a Solution im (A^2 + A) for x (A^2+A) is within the image. Linear combination properties show A^2 x + A x. Not sure where to go from here
5. ### Identity for Matrix*Vector differentiation w.r.t a vector

I have J - matrix x and y - vector d [ J(x) y(x)] / dx I can multiply the matrix and vector together and then differentiate but I think for my application it would be better to find an identity like {d [ J(x) y(x)] / dx } = J(x) d y(x) / dx + d J (x) / dx y(x) I am not sure if this identity...
6. ### Matrix Proof (Linear Systems)

Homework Statement The question relates to iterative refinement. The idea is that the computer generates a solution to the linear system Ax=b which is inexact (due to roundoff errors), denoted by x0. You then iterate the algorithm given in (1) until it converges to (something much closer to)...
7. ### Structure of a Matrix With Empty Null Space

Hi guys, I hope you are having a great day, this is Paul and, as you have seen in the title, that's what I'm looking for, let me explain: When you have a square matrix with empty null space, that is, the only solution to the equation Ax=0 (with dim(A)=n x n) is the vector x=0n x 1, means that...
8. ### The geometric shape of parametric equations

Hello everyone, I have another question mark buzzing inside my head. After the elimination steps of a matrix, I'm having some problems about imagining in 3D. For example, x=t , y=2t, z=3t what it shows us? Or, x=t+2, y=t,,z=t ? Or another examples you can think of. ( Complicated ones of...
9. ### A question about permutatioms

Homework Statement In the text, the products pq and qp of the permutations (2 3 4) and (1 3 5) were seen to be different. However, both products turned out to be 3-cycles. Is this an accident? Homework Equations p=(3 4 1)(2 5) q=(1 4 5 2) where p and q are permutations The Attempt at a...
10. ### Matlab Issue with aligning text in table format in .txt file

Homework Statement uData is a 30x5 matrix with numbers. name_Database is a 30x1 cell array with strings of Names (e.g. Fake Subject 1, Fake Subject 2, Bob). What would fix the code so that the data aligns? (please see image for the misalignment). Homework Equations The Attempt at a...
11. ### Fortran Textbook wrong?

See attached image. I have never heard that before. Why wouldn't one be able to implement a data structure that stores a matrix by its columns using C? Is that true?
12. ### Is it possible to determine a basis for non-subspace spaces?

The title may seem a little confusing and possibly stupid :D What I mean is like a plane doesn't go through the origin? Can we describe a basis for this? If so, how?
13. ### Matrix Mechanics

I would like to know more about how Heisenberg developed his matrix mechanics.He wanted to represent the quantum state in terms of observable quantities such as spectral frequencies and intensities,rather than via the more abstract wave function of Schrodinger.But how did he assemble the arrays...
14. ### Multiplication of an Identity Matrix by a Column

Homework Statement [/B] This is a seemingly simple problem. All I have to do is multiply two matrices: [ 1 0 ] [ 0 1 ] (A) and [ 2 ] [ 3 ] (B) The Attempt at a Solution [/B] Because the matrix A has the same number of columns as matrix B has rows, and because matrix A is an identity...
15. ### Matrix, solve, parametres

Homework Statement hi. i have a linear equation with parameters that i am trying to solve. unknowns are x, y and z. (12-3t)x + 2y +2z =2 x +0*y +2z =0 12x + (2-t)y + (2-t)z = 12 i am using a matrix-approach with Gaussian-elimination, and my results (for values of t which allows for a...
16. ### Finding the value of a variable in a matrix

Homework Statement Given :  x+y+5z = 2   x+2y+7z = 1   2x−y+4z = a . a) Determine the value of a which will make the given system have many solutions. Explain your answer. b) Choose a value of a which will make the given system have NO solutions. Explain your answer. c) Is it possible...
17. ### Linear Algebra: Solving a system with free variables

Here is a picture of the problem. Can anyone give me some hints on the problem? I've looked in my textbook, but I don't know what "s" means. I found stuff on the parametric vector form, and it gives me the equation x = su + tv, but I don't see any "t"'s in this problem. I first tried...
18. ### Pfaffian and determinants of skew symmetric matrices

Can anyone explain or point me to a good resource to understand these operators? I'm trying to the understand determinants for skew symmetric matrices, more specifically the Moore determinant and it's polarization of mixed determinants. Can hone shed some light? I'm confused as to how the...
19. ### [Differential Geometry] Matrix of Differential Equations in SO(3)

Homework Statement Suppose that ##s \to A(s) \subset \mathbb{M}_{33}(\mathbb{R})## is smooth and that ##A(s)## is antisymmetric for all ##s##. If ##Q_0 \in SO(3)##, show that the unique solution (which you may assume exists) to $$\dot{Q}(s) = A(s)Q(s), \quad Q(0) = Q_0$$ satisfies ##Q(s) \in...
20. ### Variable Set Distribution - Buckingham Pi Theorum

Background: I am trying to write a program for Buckingham Pi Groups. I need to find a way to list all the input varialbes as different sets. For example if I have 4 variables [V D p u] and I want to distribute them 3 ways I get 4 sets. Number of Sets = Binomial(Number of Variables...
21. ### Vector Loops and Theo Jansen

I'm studying the work of Theo Jansen and want to derive a set of general equations for motion, velocity and acceleration at each point of his linkage mechanism. I've read a general equation can be derived through the use of vector loops but I am having some trouble as my equations have 10...