What is Eigenvalue: Definition and 400 Discussions

In linear algebra, an eigenvector () or characteristic vector of a linear transformation is a nonzero vector that changes at most by a scalar factor when that linear transformation is applied to it. The corresponding eigenvalue, often denoted by



λ


{\displaystyle \lambda }
, is the factor by which the eigenvector is scaled.
Geometrically, an eigenvector, corresponding to a real nonzero eigenvalue, points in a direction in which it is stretched by the transformation and the eigenvalue is the factor by which it is stretched. If the eigenvalue is negative, the direction is reversed. Loosely speaking, in a multidimensional vector space, the eigenvector is not rotated.

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  1. S

    Find a 2x2 Matrix A for Given Eigenspaces E_2 and E_4

    Find a 2\times 2 matrix A for which E_4 = span [1,-1] and E_2 = span [-5, 6] where E_(lambda) is the eigenspace associated with the eigenvalue (lambda) relevant equations: Av=(lambda)v The Attempt at a Solution I've pretty much gotten most of the eigenspace/value problems down, but this...
  2. S

    Finding the Multiplicity of Eigenvalues for a 2x2 Matrix with a Variable Element

    For which value of k does the matrix A= |4 k| |-7 -5| have one real eigenvalue of multiplicity 2? The Attempt at a Solution - I tried by setting this problem up with det(A-(lambda)I) and trying to solve like that, but I can't seem to get it that way either. I am getting...
  3. Q

    Solving Eigenvalue Problem for Operator d2/dx2 - bx2, Function psi=e^-ax2

    Homework Statement operator is d2/dx2 - bx2 function is psi=e^-ax2 if this fuction is eigenfuction for this operator, what is "a" and "b" constants value? Homework Equations The Attempt at a Solution
  4. J

    Linear algebra show eigenvalue

    I hava a problem finding out how this is showned If A is n x n and r is not 0. Show that CrA(x) = (r^n) * CA(x/r) What rule should I think of in defanition.
  5. E

    Good book to understand eigenvalue for quantum mechanics?

    Guys I read a little on how Heisenberg's quantum mechanics equations (solving with eigenvectors) were derived in the book "What is quantum mechanics: A physical adventure". There is no exercise in the book. After reading, I still don't understand eigenvalue. What is it for? How to use it...
  6. N

    Solving the Eigenvalue Problem: Proving \ e ^ A \psi=\ e ^\lambda\psi

    Homework Statement Consider the following problem: if \ A \psi=\lambda\psi,prove that \ e ^ A \psi=\ e ^\lambda\psi Homework Equations The Attempt at a Solution This is my attempt.Please check if I am correct. If \ e ^ A \psi=\ e ^\lambda\psi is correct, we should...
  7. S

    Eigenvalue of a rotation matrix

    cos a -sin a sin a cos a How do I find the eigenvalue of this rotation matrix? I did the usual way, but didn't work! Could someone tell me how to start this problem?
  8. M

    Proving Eigenvalues and Eigenvectors for T and T*: A Comprehensive Guide

    I know that if T has eigenvalue k, then T* has eigenvalue k bar. But if T has eigenvector x, does T* also have eigenvector x? If so, how do you prove it? I don't see that in my textbook.
  9. B

    Eigenfunction, Eigenvalue, Wave Function and collapse

    Reading Sam Treiman's http://books.google.de/books?id=e7fmufgvE-kC" he nicely explains the dependencies between the Schrödinger wave equation, eigenvalues and eigenfunctions (page 86 onwards). In his notation, eigenfunctions are u:R^3\to R and the wavefunction is \Psi:R^4\to R, i.e. in contrast...
  10. T

    In an experiment, do we measure the eigenvalue or expectation value?

    In an experiment, do we measure the eigenvalue or the expectation value ? If both can be measured, how can we distinguish one from another ?
  11. J

    Obtain an eigenvector corresponding to each eigenvalue

    Homework Statement The linear operator T on R^2 has the matrix [4 -5; -4 3] relative to the basis { (1,2), (0,1) } Find the eigenvalues of T. Obtain an eigenvector corresponding to each eigenvalue.Homework Equations The Attempt at a Solution I was able to find the eigenvalues (8 and -1)...
  12. R

    Interpreting Complex Eigenvalues in Comsol Analysis

    Hey, Im working with Comsol and doing some eigenvalue analysis. Why is sometimes the eigenvalues are complex numbers and not real number frequencies? How should I interpret these complex eigenvalues? Thanks
  13. M

    What is the method for solving the eigenvalue problem with integration by parts?

    Solve the eigenvalue problem O_{6} \Psi(x) = \lambda \Psi(x) O_{6}\Psi(x) = \int from negative infinity to x of dxprime *\Psi(xprime) * xprime what values of eigenvalue \lambda lead to square integral eigenfuctions? (Hint: Differentiate both sides of the equation with respect to x) Im...
  14. S

    Functions, operator => eigenfunction, eigenvalue

    [SOLVED] Functions, operator => eigenfunction, eigenvalue Homework Statement Show, that functions f1 = A*sin(\theta)exp[i\phi] and f2 = B(3cos^{2}(\theta) - 1) A,B - constants are eigenfunctions of an operator http://img358.imageshack.us/img358/3406/98211270ob1.jpg and find...
  15. J

    Solving 1D/2D Eigenvalue Equation for Proving Function

    Hello, I want to prove that the function \mathcal{A} in the 1D case satisfy \mathcal{A}=\frac{48}{m}\sum_{j=1}^\infty \frac{\sin^2(qj/2)}{j^5}=\frac{12}{m}\left[2\zeta(5)-\text{Li}_5(e^{iq})-\text{Li}_5(e^{-iq})\right], with \text{Li}_n(z) the polylogarithm function, and the matrix...
  16. D

    Energy eigenvalue and eigen vector

    I have some question on energy eigenvalue and eigenfunction help please A particle, mass m , exists in 3 dimensions, confined in the region 0< x < 2L, 0 < y < 3L, 0 < z < 3L a) what are the energy eigenvalues and eigenfunctions of the particle? b) if the particel is a...
  17. T

    Solving WKB Eigenvalue Problem for Bound States

    Hi, This is just a quick question -- I'm puzzled by the way this answer sheet represents the potential function. The question asks us to determine the energy eigenvalues of the bound states of a well where the potential drops abruptly from zero to a depth Vo at x=0, and then increases...
  18. D

    QM - Eigenfunction / Eigenvalue Problem

    Homework Statement Find the eigenfunctions and eigenvalues for the operator: a = x + \frac{d}{dx} 2. The attempt at a solution a = x + \frac{d}{dx} a\Psi = \lambda\Psi x\Psi + \frac{d\Psi}{dx} = \lambda\Psi x + \frac{1}{\Psi} \frac{d\Psi}{dx} = \lambda x + \frac{d}{dx}...
  19. E

    The lowest energy eigenvalue

    Shankar 163 Homework Statement Show that for any normalized |psi>, <psi|H|psi> is greater than or equal to E_0, where E_0 is the lowest energy eigenvalue. (Hint: Expand |psi> in the eigenbasis of H.) Homework Equations The Attempt at a Solution I think the question assumes...
  20. E

    Eigenvalue of 0 and its physical meaning

    I need a bit of explanation on the conditions under which there is an eigenvalue that is equal to zero and what it's "physical" meaning. Thanks in advance.
  21. K

    Prove AB & BA Have Same Eigenvalues

    Homework Statement Two square matrices A and B of the same size do not commute.Prove that AB and BA has the same set of eigenvalues. I did in the following way:Please check if I am correct. Consider: det(AB-yI)*det(A) where y represents eigenvalues and I represents unit matrix...
  22. A

    Hint for Quantum Computing Question Regarding QFT's and Eigenvalue Estimation

    Homework Statement I've pasted the actual question below: http://www.zeta-psi.com/aj/qip5b.png I don't think there are many quantum computing specific things here other than the circuit (which I can derive easily if I can figure out the algorithm) Homework Equations The Quantum Fourier...
  23. N

    Small Eigenvalue Problems

    Dear experts! I have a small Hermitian matrix (7*7 or smaller). I need to find all eigenvalues and eigenvectors of this matrix. The program memory is bounded. What method is optimal in this case? Can you give any e-links? Thanks In Advance.
  24. S

    Proving \delta as Eigenvalue of Matrix A with Constant Column Sum

    eigenvalue "show that" Homework Statement Let A be a matrix whose columns all add up to a fixed constant \delta. Show that \delta is an eigenvalue of AHomework Equations The Attempt at a Solution My solution manual's hint is: If the columns of A each add up to a fixed constant \delta, then...
  25. S

    Find the Eigenvalues of the matrix and a corresponding eigenvalue

    Find the Eigenvalues of the matrix and a corresponding eigenvalue. Check that the eigenvectors associated with the distinct eigenvalues are orthogonal. Find an orthogonal matrix that diagonalizes the matrix. (1)\left(\begin{array}{cc}4&-2\\-2&1\end{array}\right) I found my eigenvalues to...
  26. P

    Continuous spectrum and weak solution of eigenvalue equation

    Hi All! Preliminaries: Let H denote the Hilbert-space, and let A be a densely defined closed operator on it, with domain $D(A) \subset H$. On D(A) one defines a finer topology than that of H such way that f_n->f in the topology on D(A) iff both f_n->f and Af_n->Af in the H-topology. Let...
  27. S

    How Do We Calculate Eigenvalues for Different Matrices?

    Hi Guys, I have got some enquires for eigenvalue and eigenvector. Consider the 1st matrix: A = [ 1 2 3] [ 0 5 6] [ 0 6 5] The characteristic polynomial is det(A-λI) = [ 1-λ 2 3] [ 0 5-λ 6] [ 0 6...
  28. B

    Solving Eigenvalue Questions for 2x2 Matrix & nxn Matrix

    I have two questions 1. If I have a 2x2 matrix A with entries a, b, c, d where a is the upper left corner, b upper right corner, c lower left, and d lower right. I have eigenvalues L1 and L2. I need to show that L1^2 + L2^2 <= a^2 + b^2 + c^2 + d^2. So far I've done this: I know...
  29. P

    Eigenvalue for DC motor convergence rate

    Hi, I have troubles solving this question: Given the general DC motor governed equation, find the control voltage such that the speed w tends to constand reference input w* and the convergence rate is determined by the desired eigenvalues L1 and L2. I think it's easy to find the control...
  30. R

    Energy eigenvalue for particle in a box

    Hello all, I'm stuck on this question, and I would appericate if someone can tell me how to start cracking the problem. I have a infinite square well, and is given a wavefunction that exist inside the well. The problem is to find the probability that a measurement of the energy will...
  31. D

    What is the Modulus of an Eigenvalue?

    :confused: :confused: :confused:
  32. M

    Eigenvalue and Eigenvector problem

    Hi Given a 3x3 matrix A = \[ \left[ \begin{array}{ccc} 0 & 0 & 1+2i \\ 0 & 5 & 0 \\ 1-2i & 0 & 4 \end{array} \right] I need to a another 3x3 which satisfacies D = U^-1 A U Step 1. Finding the eigenvalues 0 = det(A- \lambda I ) = (0- \lambda)(\lambda - 5) (\lambda -4...
  33. I

    Continuous eigenvalue of n by n matrix

    Hello, all, This is my fisrt time post on this forum, I have this question for long time but people around me couldn't really answer it, hopes I can get the answer from you guys... Given a complex n by n matrix A, Under what restriction, its eigenvalue(s) is the continuous function of A?
  34. K

    Eigenvalue Method: Solving 2nd Order ODEs

    Given:Second order ODE: x" + 2x' + 3x = 0 Find: a) Write equation as first order ODE b) Apply eigenvalue method to find general soln Solution: Part a, is easy a) y' = -2y - 3x now, how do I do part b? Do I solve it as a [1x2] matrix?
  35. Z

    Finding a vector associated with an eigenvalue

    Find a general solution of the given system using the method (A - \lambdaI)V2 = V1. x'_1 = 2x_1 - 5x_2, x'_2 = 4x_1 - 2x_2 x' = \left(\begin{array}{cc}2&-5\\4&-2\end{array}\right) characteristic equation: (2 - \lambda)((-2) - \lambda) + 20 = 0 \lambda^2 + 16 = 0 \lambda = 4i Using this...
  36. N

    Why does x-axis have eigenvalue = 1

    Why has the x-axis have an eigenvalue = 1 and the y-axis an eigenvalue =-1? (please stay simple in your answers)
  37. E

    Write down the eigenvalue equation

    Hi guys, I've been given this question as part of my homework assessment however i don't even know what its asking me to solve :( I am sure you have to apply it to a certain equation but it doesn't say what! The question is: "Write down the eigenvalue equation for the total energy operator...
  38. A

    Energy Eigenvalue: Why is (psi)n=Asin(npix/L)?

    why is (psi)n=Asin(npix/L) the energy eigenvalue?
  39. Q

    Eigenvalue problem what am i doing wrong?

    This is for a spin 1 particle. I can't get the determinant to come out right. Can someone show me what i am doing wrong
  40. J

    Study Sturm-Liouville Eigenvalue Problems

    I am studying Sturm-Liouville eigenvalue problems and their eigenfunctions form a "complete set". Can someone explain to me what this means?
  41. M

    Fourth-order eigenvalue problem

    I'm stuck on the following eigenvalue problem: u^{iv} + \lambda u = 0, 0 < x < \pi with the boundary conditions u = u'' = 0 at x = 0 and pi. ("iv" means fourth derivative) I look at the characteristic polynomial for lambda > 0 and < 0 and I get fourth roots for each of them. In the case...
  42. S

    Solve Eigenvalue Problem for ODE: Find Eigenvalue & Eigenfunctions

    I have this eigenvalue problem: \frac{\mbox{d}^2y}{\mbox{d}x^2}+\left(1-\lambda\right)\frac{\mbox{d}y}{\mbox{d}x}-\lambda y = 0 \ , \ x\in[0,1], \ \lambda\in\mathbb{R} y(0)=0 \frac{\mbox{d}y}{\mbox{d}x}(1)=0 Then, I have to show that there exists only one eigenvalue \lambda , and...
  43. O

    What is an Eigenequation and Eigenvalue in the Schrodinger Equation?

    what is an eigenequation? what is the purpose of the eigenvalue? how does this fit into the schrodinger equation (particle in a box problem) ?
  44. N

    Proving det(A) = lambda_1 * lambda_2 * ... * lambda_n for Eigenvalue A

    How do you prove that det(A) = \lambda_1*\lambda_2*...*\lambda_n, where \lambda_i is the eigenvalues of A? I'm stuck :cry:
  45. F

    Finding the eigenvalue for a given graph

    I'm having trouble finding the eigenvalue for a given graph; but more specifically I can't seem to find the characteristic polynomial. My book tells me that the characteristic polynomial of a simple graph with n vertices is the determinant of the matrix (A-\lambdaI), where A is the adjaceny...
  46. E

    Eigenvalues of O: Find Hints Here

    hi, if an operator O has the property that O^{4}f(x)=f(x), what are the eigenvalues of O? any hints on how to go about this?
  47. agro

    What is the relationship between a matrix A and its eigenvalue g when A-1 = A?

    Suppose there is a matrix A such that A-1 = A. What can we say about the eigenvalue of A, g? 1) Ax = gx 2) A-1 Ax = A-1 gx 3) Ix = g A-1x 4) x = g Ax 5) x = g gx 6) 1x = g2x Therefore 7) g2 = 1 8) g = 1 or g = -1 But suppose A = I (the identity matrix). For I, the only...
  48. P

    Solving an Eigenvalue Problem for Large n Matrix

    I am having trouble with the following question. (Just hoping to get some guidance, recommended texts etc.): "Consider an eigenvalue problem Ax = &lambda;x, where A is a real symmetric n*n matrix, the transpose of the matrix coincides with the matrix, (A)^T = A. Find all the eigenvalues and...
  49. S

    Eigenvalue and Eigenvector

    can anyone explain the the real meaning and purpose of eigen vlaue and eigen vectors.. :smile:
  50. E

    Is there an official Eigenvalue Condition in Quantum Mechanics?

    I was recently asked to explain the eigenvalue condition, but I'm sure exactly which condition the inquirer was asking about. Are any of you nerds familiar with the Eigenvalue Condition? If so, please enlighten me. eNtRopY
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