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. V

    Algebraic Multiplicity of an Eigenvalue

    Please have a look at the attached images.I am attempting a proof for the statement : The algebraic multiplicity of an eigen value λ is equal to dim null [T - λ I] dim V. Please advise me on how to move ahead. Apparently, I am at the final inference required for a proof but unable to move...
  2. I

    Eigenvalue Problem: Find All Eigen-Values & Eigen-Fns

    Homework Statement find all eigen-values and eigen-functions for the initial boundary value problem: $$x^2y''+xy'-\lambda y=0$$ Boundary Conditions: $$y(1)=y(e)=0$$ Homework EquationsThe Attempt at a Solution i just wanted to know if my substitution in the Auxiliary equation is...
  3. R

    Frequency & Eigenvalue from dynamic eqn

    Hi, i am trying to find the natural period of a vertical cantilever beam which is fixed at bottom and free at other end., i worked out the global M & K matrices and i have the eqn in the form [M]-w^2[K] = 0, the M & K are not diagonal matrices, but square symetric matrices of rank 6. i...
  4. S

    Scaling of an eigenvalue with the coupling constant

    Consider the Hamiltonian ##H = - \frac{d^2}{dx^2}+gx^{2N}##. Scaling out the coupling constant ##g##, the eigenvalues scale as ##\lambda \propto g^{\frac{2}{N+2}}##. So, we can drop the g dependence and just consider the numerical value of the eigenvalues and the associated spectral functions...
  5. H

    Help with Eigenvalue Equation and Fourier Transform

    Homework Statement Homework Equations The Attempt at a Solution I did Fourier transform directly to the eigenvalue equation and got Psi(p)=a*Psi(0)/(p^2/2m-E) But the rest, I don't even know where to start. Any opinion guys?
  6. N

    Eigenvalue distribution relation

    Hello, I was wondering if H_{ii} (that is the ith diagonal element of a random matrix) has the same distribution with its corresponding eigenvalue, say \lambda_{i}. Thanks
  7. J

    A Large scale eigenvalue problem solver

    Hi, I'm wondering what eigenvalue problem solver you are using? I'm looking for an one which could solve a very large eigenvalue problem, the matrices being ~ 100,000*100,000. Do you have any advices? Thanks.
  8. T

    Finding Eigenvalue for Ĥ: A Homework Statement

    Homework Statement Suppose: Ĥ = - (ħ2/(2m))(delta)2 - A/r where r = (x2+y2+z2) (delta)2 = ∂2/∂x2 + ∂2/∂y2 + ∂2/∂z2 A = a constant Then, show that a function of the form, f(r) = Ce-r/a with a, C as constants, is an EIGENFUNCTION of Ĥ provided that the constant a is chosen correctly. Find the...
  9. G

    Eigenvalue and and eigenvector

    Hi, I have a problem with the calculation of the eigenvalue of a matrix. That matrix is an N x N matrix which can be written as: ##M^{ab} = A\delta^{ab} + B \phi^a \phi^b## where ##\delta^{ab}## is the identity matrix and the ##\phi## is a column vector. The paper I'm studying says that...
  10. U

    What is the eigenvalue of angular momentum? (Zeeman)

    Homework Statement In the calculation of the Zeeman Effect, the most important calculation is \langle L_z + 2S_z \rangle = \langle J_z + S_z\rangle Suppose we want to find the Zeeman Effect for ##(2p)^2##, meaning ##l=1##. In Sakurai's book, My question is, what is ##m##? They say that...
  11. N

    Eigenvalue, Eigenvector and Eigenspace

    Let's say my eigenvalue λ=-1 and we assume eigenvector of zero are non-eigenvector. An eigenspace is mathematically represented as Eλ = N(λ.In-A) which essentially states, in natural language, the eigenspace is the nullspace of a matrix. N(λ.In-A) is a matrix. Would it then be valid to say...
  12. M

    Description of eigenvector corresponding to each eigenvalue.

    I have a problem I need to solve. I can't find anything in my book that tells me how to do it. It might be worded differently in the book, but I'm not 100% sure how to solve this. Homework Statement Give a description of the eigenvectors corresponding to each eigenvalue. The Attempt at a...
  13. M

    How to apply boundary condition in generalized eigenvalue problem?

    Hi all, Generally boundary condition (Dirichlet and Neumann) are applied on the Load Vector, in FEM formulation. The equation i solved, is Generalized eigenvalue equation for Scalar Helmholtz equation in homogeneous wave guide with perfectly conducting wall ( Kψ =λMψ ), and found, doesn't...
  14. M

    Solving Matrix Eigenvalue Equation for ψ_{200} and ψ_{210} States

    In order to apply perturbation theory to the ψ_{200} and ψ_{210} states, we have to solve the matrix eigenvalue equation. Ux=λx where U is the matrix of the matrix elements of H_{1}= eEz between these states. Please see the matrix in attachment 1. where <2,0,0|z|2,1,0>=<2,1,0|z|2,0,0>=3a_{o}...
  15. M

    MHB Eigenvalue problem of the form Sturm-Liouville

    Hey! :o I have the following exercise and I need some help.. $"\text{The eigenvalue problem } Ly=(py')'+qy=λy, a \leq x \leq b \text{ is of the form Sturm-Liouville if it satisfies the boundary conditions } p(a)W(u(a),v^*(a))=p(b)W(u(b),v^*(b)). \text{ Show that the boundary conditions of the...
  16. K

    Eigenvalue problem with nonlocal condition

    Hello guys, suppose we have an eigenvalue problem \left\{ \begin{array}{ll} u'' + λu = 0, \quad x \in (0,\pi) \\ u(0)=0 \quad \\ \left( \int_0^\pi \! {(u^+)}^2 \, \mathrm{d}x \right)^{\frac{1}{2}} = \left( \int_0^\pi \! {(u^-)}^4 \, \mathrm{d}x \right)^\frac...
  17. maajdl

    Singular value decomposition and eigenvalue problem:

    Could you explain me: what the difference is between singular value decomposition and eigenvalue problem, when square matrices are involved. Thanks
  18. N

    Understanding the Eigenvalue Problem for a 4x4 Matrix with Rank 1 and Trace 10

    Homework Statement Let there be a 4X4 Matrix A with dim(im(A), or rank = 1 , and trace=10. What are the Eigenvalues of A? Are there any multiplicities? The Attempt at a Solution While I understand that the trace of a matrix that's 4X4 = the sum of the diagonal elements, I'm confused...
  19. S

    MHB Eigenvalue separation of a Block Matrix with a special structure

    Hi everyone, I have a square matrix J \in \mathbb{C}^{2n \times 2n} where, $J=\left(\begin{array}{cc}A&B\\\bar{B}&\bar{A}\end{array}\right)$ A \in \mathbb{C}^{n \times n} and its conjugate \bar{A} are diagonal.Assume the submatrices A,B \in \mathbb{C}^{n \times n} are constructed in a way...
  20. C

    MHB Show V=Cx iff there are no multiple eigenvalue

    $L: V\to V$ a diagonalizable linear operator on finite-dim vector space. show that $V = C_x$ iff there are no multiple eigenvalues ------- here $C_x = \operatorname{span} \{x, L(x), L^2(x), \cdots\}$ basically it is a cyclic subspace generated by x that belongs to V. edit: solved
  21. D

    Eigenvalue of the system and the one of its part

    Dear all, I have a problem about the eigenvalue of the system and the eigenvalue of the part of the system. For example,in the theory of the APW method,the space of the primitive cell is divided into muffin-tin (MT) spheres and the interstitial region (IR). In order to gain the...
  22. L

    Eigenvalue of angular momentum operator

    Homework Statement I'm running through practice papers for my 3rd year physics exam on atomic and nuclear physics: This is the operator we found in the previous part of the question L = -i*(hbar)*d/dθ Next, we need to find the eigenvalues and normalised wavefunctions of L The...
  23. M

    Eigenvalue Vector x: Question 1 and 2

    Question one: in regards to two segments underlined in blue. If (a,x) is an eigenvalue and vector of A, that means Ax = ax, where a is a real number. My question is, is Amx = amx, where m in an integer greater than 1? Question 2: in regards to two segments underlined in red. I...
  24. H

    Quick question about solving an eigenvalue problem

    I just have a question about the problem for when the eigenvalue = 0 Homework Statement for y_{xx}=-\lambda y with BC y(0)=0 , y'(0)=y'(1) Homework Equations The Attempt at a Solution y for lamda = 0 is ax+b so from BC: y(0)=b=0 and a=a What is the conclusion to...
  25. C

    Show that +1 is an eigenvalue of an odd-dimensional rotation matrix.

    Homework Statement The probelm is to show, that a rotation matrix R, in a odd-dimensional vector space, leaves unchanged the vectors of at least an one-dimensional subspace. Homework Equations This reduces to proving that 1 is an eigenvalue of Rnxn if n is odd. I know that a rotational...
  26. T

    What is an eigenvalue problem?

    Are eigenvalue problems and boundary value problems (ODEs) the same thing? What are the differences, if any? It seems to me that every boundary value problem is an eigenvalue problem... Is this not the case?
  27. B

    Prove true or false eigenvalue question

    Homework Statement Prove true or false. If A^2+A=0 then λ=1 may not be an eigenvalue. Homework Equations To find the eigenvalues of A I find the solutions to det(λ-A). The definition of an eigenvalue from my understanding, AX = λX. A(A+I) = 0 The Attempt at a Solution...
  28. K

    MHB Eigenvector and eigenvalue for differential operator

    My friends and I have been struggling with the following problem, and don't understand how to do it. We have gotten several different answers, but none of them make sense. Can you help us? **Problem statement:** Let $V$ be the vector space of real-coefficient polynomials of degree at most $3$...
  29. K

    How to solve a system of PDAEs with eigenvalue

    I have the following system of partial differential algebraic equations: [ tex ] \frac{1}{H_p}\frac{\partial H_p}{\partial t} = - \frac{\partial W_p}{\partial x} - \frac{f1(H_p,c_p,W_p)}{H_p}, [ \tex ] [tex] \frac{1}{H_p}\frac{\partial}{\partial t}(H_p c_p} = - \frac{\partial}{\partial...
  30. D

    MHB Eigenvalue and eigenfunction for Fredholm method

    Given \[ f(x) = \lambda\int_0^1xy^2f(y)dy \] At order \(\lambda^2\) and \(\lambda^3\), we have repeated zeros so \[ D(\lambda) = 1 - \frac{\lambda}{4}. \] Then we have \[ \mathcal{D}(x, y;\lambda) = xy^2 \] so \[ f(x) = \frac{\lambda}{D(\lambda)}\int_0^1\mathcal{D}(x, y;\lambda)dy. \] How do I...
  31. Petrus

    MHB When there is a double root for the eigenvalue, how many eigenvectors?

    Hello MHB, I got one question. If I want to find basis ker and it got double root in eigenvalue but in that eigenvalue i find one eigenvector(/basis) what kind of decission can I make? Is it that if a eigenvalue got double root Then it Will ALWAYS have Two eigenvector(/basis)? Regards, |\pi\rangle
  32. D

    MHB Eigenvalue (and function) of integral equation

    Given \[ f(x) = \lambda\int_0^1xy^2f(y)dy \] I am trying to determine the eigenvalues and eigenfunction. I know that the \(\frac{1}{\lambda}\) are the eigenvalues. We can write \(f(x) = xA\) and \(A = \lambda\int_0^1y^2f(y)dy\). \[ A\Bigg(1 - \lambda\int_0^1y^3dy\Bigg) = 0\quad (*) \] So is...
  33. V

    Two-Degree-Of-Freedom Linear System: Eigenvalue problem

    I've found the characteristic equation of the system I'm trying to solve: $$ω^{4}m_{1}m_{2}-k(m_{1}+2m_{2})ω^{2}+k^{2}=0$$ I now need to find the eigenfrequencies, i.e. the two positive roots of this equation, and then find the corresponding eigenvectors. I've been OK with other examples...
  34. P

    Reducing angular Schrodinger equation to eigenvalue problem

    Homework Statement The angular part of the Schrodinger equation for a positron in the field of an electric dipole moment {\bf d}=d{\bf \hat{k}} is, in spherical polar coordinates (r,\vartheta,\varphi), \frac{1}{\sin\vartheta}\frac{\partial}{\partial\vartheta} \left( \sin\vartheta\frac{\partial...
  35. H

    Eigenvalue for harmonic oscillator

    Homework Statement The Hamiltonian for a particle in a harmonic potential is given by \hat{H}=\frac{\hat{p}^2}{2m}+\frac{Kx^2}{2}, where K is the spring constant. Start with the trial wave function \psi(x)=exp(\frac{-x^2}{2a^2}) and solve the energy eigenvalue equation...
  36. Barioth

    MHB Find the eigenvalue of a linear map

    Hi everyone, I have this linear map A:R^3 \rightarrow R^3 I have that A(v)=v-2(v\dot ô)ô); v,ô\in R^3 ;||ô||=1 I know that A(A(v))=v this telling me that A is it's own inverse. From there, how can I find the eigenvalue of A? Thanks
  37. A

    Find the Largest Eigenvalue & Eigenvector of A

    A=a.a', where a is an N by 1 vector,a'a=5,and T is transpose. a)Give the largest eigenvalue of A. b)what is the corresponding eigenvector? Please help me to solve the problem.
  38. R

    Dosen't energy eigenvalue depend on x?

    there is potential V(x). If at some point x=a wavefunction have some energy eigenvalue, then Is it guaranteed that It has same energy throughout whole region? Where can I find explanation about this?
  39. J

    Eigenvalue problem and initial-value problem?

    Hi all, I want to ask a question about the eigenvalue problem (EVP) and the initial value problem (IVP). Let's say we are solving this linear equation \frac{\partial u}{\partial t}=\mathcal{L}u, the operator L is dependent on some parameters like Reynolds number. I first check the...
  40. B

    Is the geometric multiplicity of an eigenvalue a similar invariant?

    If two matrices similar to one another are diagonalizable, then certainly this is the case, since the algebraic multiplicity of any eigenvalue they share must be equal (since they are similar), and since they are diagonalizable, those algebraic multiplicities must equal the geometric...
  41. M

    Eigenvalue of product of matrices

    I have two real symmetric matrices A and B with the following additional properties. I would like to know how the eigenvalues of the product AB, is related to those of A and B? In particular what is \mathrm{trace}(AB)? A contains only 0s on its diagonal. Off diagonal terms are either 0 or...
  42. A

    Motivation behind eigenvalue and eigenvector

    An eigenvector is defined as a non-zero vector 'v' such that A.v = λ.v I don't understand the motive behind this. We are trying to find a vector that when multiplied by a given square matrix preserves the direction of the vector. Shouldn't the motive be the opposite i.e. finding the matrix...
  43. J

    Finding the change in the eigenvalue without knowing the change in the

    Hello, I am currently teaching myself quantum mechanics using MIT's OCW and am suck on the following problem from the second problem set of the 2005 7.43 class. Homework Statement Consider an operator O that depends on a parameter λ and consider the λ-dependent eigenvalue equation...
  44. R

    Odd Form Of Eigenvalue - Coupled Masses

    Odd Form Of Eigenvalue -- Coupled Masses This isn't strictly homework, since it's something I'm trying to self-teach, but it seems to fit best here. Homework Statement It's an example of applying eigenvalue methods to solve (classical) mechanical systems in an introductory text to QM...
  45. W

    How to solve eigenvalue problems with mixed boundary condition?

    suppose function f is define on the interval [0,1] it satisfies the eigenvalue equation f'' + E f=0, and it satisfies the boundary conditions f'(0)+ f(0)=0, f(1)=0. How to solve this eigenvalue problem numerically? the mixed boundary condition at x=0 really makes it difficult
  46. W

    Eigenvalue problem with operators as matrix elements

    Hello, I have a feeling that the solution to this question is going to be incredibly obvious, so my apologies if this turns out to be really dumb. How do I solve the following eigenvalue problem: \begin{bmatrix} \partial_x^2 + \mu + u(x) & u(x)^2 \\ \bar{u(x)}^2 & \partial_x^2 + \mu +...
  47. L

    Find eigenvalue for matrix B= {[3,4,12],[4,-12,3],[12,3,-4]}

    Homework Statement Find eigenvalue for matrix B= {[3,4,12],[4,-12,3],[12,3,-4]} Homework Equations The Attempt at a Solution I set up the charactersitic polynomial and got the equation: Pa(x) = (x-3)(x+12)(x+4) = x3 + 132 - 144 + 144 = x3 + 132 So I have 3 eigenvalues: 0...
  48. T

    Repeated Eigenvalue of a n=3 system of differential equations

    Homework Statement x' = \begin{pmatrix}0&1&3\\2&-1&2\\-1&0&-2\end{pmatrix}*x The Attempt at a Solution I've found the repeated eigenvalues to be λ_{1,2,3}=-1 I've also found the first (and only non zero eigenvector) to be \begin{pmatrix}1&2&-1\end{pmatrix}, but I'm not entirely...
  49. P

    Solving Eigenvalue Problem After Galerkin

    Eigenvalue problem after galerkin Homework Statement i am working on vibration of cylindrical shell analysis, after solving the equations of motion by galerkin method , i reach to an eigenvalue problem this way : { p^2*C1+p*C2+C3 } * X=0 C1,C2,C3 are all square matrices of order n*n...
  50. J

    How Do You Solve Modified Eigenvalue Problems Like Lq=\lambda q + a?

    I know that eigenvalue problem like Lq=\lambda q could be easily solved by eig command in Matlab. But how to solve a problem like Lq=\lambda q + a, where a has the same dimension with the eigenfunction q? Thanks a lot in advance. Jo
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