Problem Set 10 - Physics 424 Quantum Mechanics Fall 2015 Reading\/Homework Assignment 10 Due in Class Friday Reading Townsend Chapter 9 Translational and

# Problem Set 10 - Physics 424 Quantum Mechanics Fall 2015...

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Physics 424: Quantum Mechanics, Fall 2015Reading/Homework Assignment 10Due in Class Friday, 12/4/151ReadingTownsend Chapter 9 - Translational and Rotational Invariance. We willskip the following sections and you do not need them for the homeworkor exams:Sec. 9.2 – Translational Invariance.Sec. 9.3 – COM Coordinates.Sec. 9.7 – Diatomic Molecules.You should read all of Ch. 9 apart from the three sections listed above.Start reading Townsend Chapter 10 – Bound State of Central Poten-tials. You don’t need Ch. 10 for this homework set, but we will startdiscussing it in class.Problems to work out and turn in (60 pts total)1. (10 pts) Using the position-space representation of the position andmomentum operators in 3Dˆx|ψi ↔xψ,ˆy|ψi ↔yψ . . .ˆpx|ψi ↔ -i¯h∂ψ∂x,ˆpy|ψi ↔ -i¯h∂ψ∂y. . .(1)prove the following canonical commutation relationsxj,ˆpk] =i¯jk,ˆIxj,ˆxk] =ˆ0,pj,ˆpk] =ˆ0.(2)Do this by applying the operators of Eq. 1 to an arbitary wave functionψ(x, y, z). Here we are using the same notation as Townsend Sec. 9.1,so for example ˆx2= ˆy. Sincejandkcan each be 1, 2, or 3 there are inprinciple 27 commutation relations to show in Eq. 2. However, it willsuffice for you to prove a much smaller number of examples and thenargue that the remaining relations are proved in the same way.

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• Fall '15
• mechanics, Work, Townsend, commutation relations, canonical commutation relations, 3D ISW