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Postulates and Basic Elements of Quantum Mechanics: Properties of Operators

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Part of the book series: UNITEXT for Physics ((UNITEXTPH))

Abstract

In this chapter I present a somewhat more formal introduction to the theory that underlies quantum mechanics. Although the discussion is limited mainly to single particles, many of the results apply equally well to many-particle systems. Some of the postulates of the theory depend on the properties of Hermitian operators, operators that play a central role in quantum mechanics. First I state the postulates, then discuss Hermitian operators, and finally explore some results that follow directly from Schrödinger’s equation.

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Notes

  1. 1.

    The fact that \(\left \vert c_{12}\right \vert <1\) follows from the Schwarz inequality, \(\left \vert \left ( \psi _{a_{n}}^{(1)},\psi _{a_{n}}^{(2)}\right ) \right \vert ^{2}\leq \left ( \psi _{a_{n}}^{(1)},\psi _{a_{n}}^{(1)}\right ) \left ( \psi _{a_{n}}^{(2)},\psi _{a_{n}}^{(2)}\right ) =1.\)

  2. 2.

    Note that, in the momentum representation, the eigenfunctions of \(\hat {p}\) are Φ q (p) = δ(p − q) and the eigenfunctions of \(\hat {x}\) are \(\Phi _{x}(p)=e^{-ipx/\hbar }/\sqrt {2\pi \hbar }\).

  3. 3.

    See, for example, M. O. Scully and M. S. Zubairy, Quantum Optics (Cambridge University Press, Cambridge, U.K., 1997), Chapter 19.

  4. 4.

    Experiments of this type were pioneered in the group of Serge Haroche, who was awarded the Nobel prize in recognition of these and other experiments.

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Berman, P.R. (2018). Postulates and Basic Elements of Quantum Mechanics: Properties of Operators. In: Introductory Quantum Mechanics. UNITEXT for Physics. Springer, Cham. https://doi.org/10.1007/978-3-319-68598-4_5

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