Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Does this operator commute with the Hamiltonian operator?

  1. Dec 3, 2017 #1
    1. The problem statement, all variables and given/known data
    Show that the mean value of a time-independent operator over an
    energy eigenstate is constant in time.

    2. Relevant equations
    Ehrenfest theorem

    3. 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?
     
  2. jcsd
  3. Dec 3, 2017 #2

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    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##?
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted