Schroedinger Equation in Momentum Space

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SUMMARY

The discussion focuses on deriving the Schrödinger equation for a harmonic oscillator in momentum space. The equation is presented as ih∂Φ(p)/∂t = (p²/2m)Φ(p) - ℏ²∂²Φ(p)/∂p², confirming its validity without electrodynamics. Participants clarify that the potential V and its derivatives must be evaluated at zero, not at x. The final form of the generalized Schrödinger equation is also confirmed, ensuring accurate representation of kinetic energy and potential terms.

PREREQUISITES
  • Understanding of quantum mechanics principles, specifically the Schrödinger equation.
  • Familiarity with momentum space representation in quantum mechanics.
  • Knowledge of harmonic oscillators and their mathematical formulations.
  • Basic calculus, particularly partial derivatives and series expansions.
NEXT STEPS
  • Study the derivation of the Schrödinger equation in position space for comparison.
  • Learn about the implications of potential energy functions in quantum mechanics.
  • Explore the mathematical techniques for solving partial differential equations in physics.
  • Investigate the role of boundary conditions in quantum mechanical systems.
USEFUL FOR

Students and professionals in physics, particularly those specializing in quantum mechanics, theoretical physicists, and anyone interested in the mathematical foundations of the Schrödinger equation.

Domnu
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Problem
Derive the Schroedinger equation (for harmonic oscillator) in momentum space.

The attempt at a solution
We have

[tex]ih \frac{\partial}{\partial t} \langle p' | \alpha \rangle = \langle p' | \frac{p^2}{2m} | \alpha \rangle + \langle p' | V(x) | \alpha \rangle[/tex]
[tex]\iff ih \frac{\partial}{\partial t} \langle p' | \alpha \rangle = \frac{p'^2}{2m}\langle p' | \alpha \rangle + \left(i\hbar\frac{\partial}{\partial p'}\right)^2 \langle p' | \alpha \rangle[/tex]
[tex] \[<br /> \iff ih\frac{\partial \Phi(p)}{\partial t} = \frac{p^2}{2m}\Phi(p) - \hbar^2 \frac{\partial^2 \Phi(p)}{\partial p^2}<br /> \][/tex]

Is the above correctly done? If so, is this the generalized Schroedinger equation (without electrodynamics, etc.. just p^2/2m kinetic energy)?:

[tex] \[<br /> \iff ih\frac{\partial \Phi(p)}{\partial t} = \frac{p^2}{2m}\Phi +\displaystyle\sum_{n = 0}^\infty \frac{V^{(n)}(0)}{n!}\left(i\hbar \frac{\partial}{\partial p}}\right)^n \Phi<br /> \][/tex]

Thanks very much for your help :)
 
Last edited:
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Yes and yes (but V and its derivatives should be evaluated at 0, not x).
 
Avodyne said:
Yes and yes (but V and its derivatives should be evaluated at 0, not x).

Yes, sorry that was a typo. :) Thanks very much!
 

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