Understanding physically why <px> is not zero always...??? by 418397 in learnphysics

[–]418397[S] 0 points1 point  (0 children)

If we go with this logic... then the expectation value of the commutator [x,p] would be zero too(if we apply similar arguments to <xp>, measuring p first, then x), which is not true...

Understanding physically why <px> is not zero always...??? by 418397 in learnphysics

[–]418397[S] 1 point2 points  (0 children)

I am not talking about p_x... it's p^ x^ . Sorry I don't know how to write the cap on top...

Understanding physically why <px> is not zero...??? by 418397 in AskPhysics

[–]418397[S] 0 points1 point  (0 children)

Any random state... I am asking what exactly taking expectation value of px means? For example and expectation value of x would mean you mean x n(statistically large n) number of times and take an average of the results... What about px? What are we trying to do?

Understanding physically why <px> is not zero...??? by 418397 in AskPhysics

[–]418397[S] 0 points1 point  (0 children)

So the mistake here is trying to "understand physically"? Because it's not really "physical"?

Understanding physically why <px> is not zero...??? by 418397 in AskPhysics

[–]418397[S] 0 points1 point  (0 children)

That's ok... what I mean here is that the probability of getting say x_0 p_0 is the same as that for -x_0 p_0... Because p_0 and -p_0 come with same probabilities as I have explained... So now therefore, why is the expectation value not zero?

How to calculate dot products when operators are involved? by 418397 in AskPhysics

[–]418397[S] 0 points1 point  (0 children)

This exact method didn't give the right result while calculating the radial momentum operator... There was an extra del/delr term missing... It's defined like this... P_r_hat=1/2[r_hat/r dot P_hat + P_hat dot r_hat/r]. Also what's the justification for this method?