Do p and σz Commute?

[Niles]

Homework Statement

Hi

I want to find the commutator between the momentum operator p and σ_z, the third Pauli spin matrix. I am not quite sure how to get started on this one. Can I get a push in the right direction?

For the record, I would say that it is zero since they act on different spaces. Is this correct?


Niles.

 

[quantum13]

I think it's important to specify a direction for the momentum operator. I think that, if it's x-momentum and z-spin and you measure x-momentum to be zero every time then you know that the spin vector is probably in the x direction telling you for sure that z-spin is zero, meaning they don't commute.

 

[Niles]

I was right, they do commute. See more here: https://www.physicsforums.com/showthread.php?t=396031

Regards,
Niles.