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Eigenfunctions corresponding to a particular energy value

  1. Aug 9, 2014 #1
    Suppose we want to get eigenfunctions of a One-Particle Hamiltonian corresponding to one of its eigenvalues, say E, in bases of free particle eigenfunctions (plane waves). Can we use the plane waves corresponding to energies near E to get a reasonable solution?
  2. jcsd
  3. Aug 9, 2014 #2


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    No it depends entirely on the Hamiltonian. This isn't like the variational principle where just about any trial wave-function gives you a good estimate of the ground state energy. You're trying to go backwards and it can certainly fail to give a good approximation in general. For example, the plane wave is an absolutely terrible approximation of the ground state wave-function of the harmonic oscillator. You can't approximate a Gaussian with a sinusoid.
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