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  2. Eigenfunction - Wikipedia

    en.wikipedia.org/wiki/Eigenfunction

    Its eigenfunctions form a basis of the function space on which the operator is defined [5] As a consequence, in many important cases, the eigenfunctions of the Hermitian operator form an orthonormal basis. In these cases, an arbitrary function can be expressed as a linear combination of the eigenfunctions of the Hermitian operator.

  3. Eigenvalues and eigenvectors of the second derivative

    en.wikipedia.org/wiki/Eigenvalues_and...

    These formulas are used to derive the expressions for eigenfunctions of Laplacian in case of separation of variables, as well as to find eigenvalues and eigenvectors of multidimensional discrete Laplacian on a regular grid, which is presented as a Kronecker sum of discrete Laplacians in one-dimension.

  4. Eigenvalues and eigenvectors - Wikipedia

    en.wikipedia.org/wiki/Eigenvalues_and_eigenvectors

    Using the Leibniz formula for determinants, the left-hand side of equation is a polynomial function of the variable λ and the degree of this polynomial is n, the order of the matrix A. Its coefficients depend on the entries of A , except that its term of degree n is always (−1) n λ n .

  5. Complete set of commuting observables - Wikipedia

    en.wikipedia.org/wiki/Complete_set_of_commuting...

    The compatibility theorem tells us that a common basis of eigenfunctions of ^ and ^ can be found. Now if each pair of the eigenvalues ( a n , b n ) {\displaystyle (a_{n},b_{n})} uniquely specifies a state vector of this basis, we claim to have formed a CSCO: the set { A , B } {\displaystyle \{A,B\}} .

  6. Mathematical formulation of quantum mechanics - Wikipedia

    en.wikipedia.org/wiki/Mathematical_formulation...

    The mathematical formulations of quantum mechanics are those mathematical formalisms that permit a rigorous description of quantum mechanics.This mathematical formalism uses mainly a part of functional analysis, especially Hilbert spaces, which are a kind of linear space.

  7. Variational method (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Variational_method...

    Suppose we are given a Hilbert space and a Hermitian operator over it called the Hamiltonian.Ignoring complications about continuous spectra, we consider the discrete spectrum of and a basis of eigenvectors {| } (see spectral theorem for Hermitian operators for the mathematical background): | =, where is the Kronecker delta = {, =, and the {| } satisfy the eigenvalue equation | = | .

  8. Position operator - Wikipedia

    en.wikipedia.org/wiki/Position_operator

    The eigenfunctions of the position operator (on the space of tempered distributions), represented in position space, are Dirac delta functions. Informal proof. To show that possible eigenvectors of the position operator should necessarily be Dirac delta distributions, suppose that ψ {\displaystyle \psi } is an eigenstate of the position ...

  9. Spin contamination - Wikipedia

    en.wikipedia.org/wiki/Spin_contamination

    In computational chemistry, spin contamination is the artificial mixing of different electronic spin-states.This can occur when an approximate orbital-based wave function is represented in an unrestricted form – that is, when the spatial parts of α and β spin-orbitals are permitted to differ.