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Given an n × n square matrix A of real or complex numbers, an eigenvalue λ and its associated generalized eigenvector v are a pair obeying the relation [1] =,where v is a nonzero n × 1 column vector, I is the n × n identity matrix, k is a positive integer, and both λ and v are allowed to be complex even when A is real.l When k = 1, the vector is called simply an eigenvector, and the pair ...
The eigenvalues are real. The eigenvectors of A −1 are the same as the eigenvectors of A. Eigenvectors are only defined up to a multiplicative constant. That is, if Av = λv then cv is also an eigenvector for any scalar c ≠ 0. In particular, −v and e iθ v (for any θ) are also eigenvectors.
For defective matrices, the notion of eigenvectors generalizes to generalized eigenvectors and the diagonal matrix of eigenvalues generalizes to the Jordan normal form. Over an algebraically closed field, any matrix A has a Jordan normal form and therefore admits a basis of generalized eigenvectors and a decomposition into generalized eigenspaces .
The surviving diagonal elements, ,, are known as eigenvalues and designated with in the defining equation, which reduces to =. The resulting equation is known as eigenvalue equation . [ 5 ] The eigenvectors and eigenvalues are derived from it via the characteristic polynomial .
It is used in all applications that involve approximating eigenvalues and eigenvectors, often under different names. In quantum mechanics , where a system of particles is described using a Hamiltonian , the Ritz method uses trial wave functions to approximate the ground state eigenfunction with the lowest energy.
In mathematics, an eigenvalue perturbation problem is that of finding the eigenvectors and eigenvalues of a system = that is perturbed from one with known eigenvectors and eigenvalues =. This is useful for studying how sensitive the original system's eigenvectors and eigenvalues x 0 i , λ 0 i , i = 1 , … n {\displaystyle x_{0i},\lambda _{0i ...
Matrix multiplication shares some properties with usual multiplication. However, matrix multiplication is not defined if the number of columns of the first factor differs from the number of rows of the second factor, and it is non-commutative, [10] even when the product remains defined after changing the order of the factors. [11] [12]
The eigenvalues are thus the roots of the polynomial det ( x I − M ) . {\displaystyle \det(xI-M).} If V is of dimension n , this is a monic polynomial of degree n , called the characteristic polynomial of the matrix (or of the endomorphism), and there are, at most, n eigenvalues.