Does this operator commute with the Hamiltonian operator?

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SUMMARY

The discussion centers on demonstrating that a time-independent operator commutes with the Hamiltonian operator in quantum mechanics. The Ehrenfest theorem is referenced as a key principle in establishing that the mean value of such an operator remains constant over time when applied to energy eigenstates. The participants explore the relationship between the operator and the Hamiltonian, emphasizing that both acting on energy eigenstates implies they commute. The time-dependent form of the energy eigenfunction is also queried, specifically how it evolves from its initial state.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly the Hamiltonian operator.
  • Familiarity with the Ehrenfest theorem and its implications.
  • Knowledge of energy eigenstates and their properties.
  • Basic grasp of time-dependent Schrödinger equation.
NEXT STEPS
  • Study the proof of the Ehrenfest theorem in detail.
  • Learn about the commutation relations in quantum mechanics.
  • Investigate the time evolution of quantum states using the time-dependent Schrödinger equation.
  • Explore examples of operators that commute with the Hamiltonian in various quantum systems.
USEFUL FOR

Students of quantum mechanics, physicists working on quantum systems, and anyone interested in the mathematical foundations of operator theory in quantum physics.

tarkin
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Homework Statement


Show that the mean value of a time-independent operator over an
energy eigenstate is constant in time.

Homework Equations


Ehrenfest theorem

The Attempt at a Solution


I get most of it, I'm just wondering how to say/show that this operator will commute with the Hamiltonian operator.
Is it correct to say that because they both act on energy eigenstates, they must commute?
If so, is there a way to show this?
 
Physics news on Phys.org
What is the form of the time-dependent energy eigenfunction? Say at ##t=0## this eigenfunction is ##|n\rangle## having energy ##E_n##, how does it look like at a later time ##t##?
 

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