# Eigenfunctions in Hilbert Space, Infinite Square Wells and Uncertainty

Hi I'm kinda stuck with a couple quantum HW questions and I was wondering if you guys could help.

First, Is the ground state of the infinite square well an eigenfunction of momentum?? If so, why. If not, why not??

Second, Prove the uncertainty principle, relating the uncertainty in position (A=x) to the uncertainty in energy ([tex]B=p^2/(2m + V)[\tex]):

[tex]\sigma x\sigma H \geq \hbar/2m |<P>|[\tex]

For stationary states this doesn't tell you much -- why not??

And finally, Show that two noncommuting operators cannot have a complete set of common eigenfunctions. Hint: Show that if P(operator) and Q(operator) have a complete set of common eigenfunctions, the [P(operator),Q(operator)]f = 0 for any function in Hilbert space.

thanks in advance, Rob.

## Answers and Replies

Also can someone tell me why the code thingy for the formulas ain't working??

vanesch
Staff Emeritus
Science Advisor
Gold Member
Also can someone tell me why the code thingy for the formulas ain't working??

Because the end tag of the tex part is [ / tex ] and not [ \ tex ]