826 reputation
426
bio website ziga-lausegger.netau.net/…
location Slovenia
age 28
visits member for 2 years, 7 months
seen Feb 24 at 9:43

I love to program and crosscompile baremetal C programs for ARM based microcontrollers, I love physics and i love writing science documents/books in LaTeX. It amazes me how physics is connecting all science and is helping mathematics to evolve. In order for science profession to comunicate on a high level i advise everyone to use Linux, LaTeX and a good vector imaging program like Inkscape.


Aug
15
comment The probability of finding the electron in the H-atom
Thank you very much. So if we are satisfied with a fraction of a probability there is no need to integrate :) What confused me was that feeling that if we want to integrate the equation we have to do it on both sides and not only one side... It is weird to me that we integrate just part of the equation.
Aug
15
asked The probability of finding the electron in the H-atom
Aug
8
asked Quantum tunelling problem - got a weird imaginary ratio in the end
Aug
7
comment Moving electron - finding the wavefunction
Thank you very much for the extended anwser. Now i do understand.
Aug
7
accepted Moving electron - finding the wavefunction
Aug
7
comment Moving electron - finding the wavefunction
Well the Lorentz invariance is a fundamantal equation of relativity and it says that $E=E_0$. If i then use $E=E_k$ to calculate constant $L$ it seems to me that i have violated the special relativity and everything Einstein wrote...
Aug
7
comment Moving electron - finding the wavefunction
I do not understand...
Aug
7
asked Moving electron - finding the wavefunction
Aug
7
comment QM - calculating expectation value for velocity of an electron
After looking at @Ali's anwser I believe that you meant "momentum operator" instead of the "velocity operator". Thanks for pointing this out as i wasn't sure if i d get $\langle v \rangle^2$ or $\rangle v^2 \langle$ using the kinetic energy method - i guess it is the later huh - can i ask you, how do we know this? Why do we know that by using the kinetic energy method we get $\langle v^2\rangle$ and not $\langle v\rangle^ 2$? For the solution i will take Ali-s anwser.
Aug
7
accepted QM - calculating expectation value for velocity of an electron
Aug
7
comment QM - calculating expectation value for velocity of an electron
Regarding your 1st paragraph. Why did you use the energy $\langle E \rangle$ and an operator $\hat{H}$ instead of $\langle E_k \rangle$ and an operator $\langle \hat{T}\rangle$?
Aug
7
comment QM - calculating expectation value for velocity of an electron
I will be satisfied with only a magnitude so far ... don-t know enough of QM yet to think about QM vectors :). Do zou think this classical approximation is good enough for a particle in a box. I mean i calculated $\langle E_k \rangle=338.79eV$.
Aug
7
comment QM - calculating expectation value for velocity of an electron
So this is not possible? $\langle E_k\rangle = \tfrac{1}{2}m\langle v \rangle^2 \longrightarrow \langle v\rangle = \sqrt{2 \langle E_k \rangle / m}$
Aug
7
comment QM - calculating expectation value for velocity of an electron
I have discovered that in this PDF they diferentiate the wavefunction over time but i have a stationary state! Do i have to multiply it with $\exp\frac{i}{\hbar E t}$ and then diferentiate it? Is there any easier way if i already calculated expectation value for kinetic energy $\langle T \rangle$?
Aug
7
comment QM - calculating expectation value for velocity of an electron
Never mind I found it in this PDF - page 32 - Now give me some downvotes for being lazy :D
Aug
7
comment QM - calculating expectation value for velocity of an electron
Well i asked this because I cant find an anwser in my book which only describes operators of kinetic energy, potential energy, momentum, position and position square... If i write expectation value for speed, Google returns mostly these same operators...
Aug
7
comment Wavefunction as a combination of two stationary states - how to find those states?
Thank you very much. Ok so if we scalar multiply the stationary state $\phi_i$ with a wavefunction $\psi$ and integrate over $x$ we should get the constant $c_i$ which is normaly in front of an stationary state? How come?
Aug
7
comment Wavefunction as a combination of two stationary states - how to find those states?
Oh i see if there is a cosinus the problem becomes much harder.
Aug
7
asked QM - calculating expectation value for velocity of an electron
Aug
7
comment Wavefunction as a combination of two stationary states - how to find those states?
@Sebastian Henckel I know that if the problem is on an interval $0<x<d$ the solutions are all like $\sin(n\pi x/d)$ but I wondered if i had a problem like this: $\psi= A\left[ \cos \left(\frac{7 \pi x}{d}\right) + \frac{1}{3}\sin \left(\frac{4 \pi x}{d}\right)\right]$ could i reckognize this as a superposition of states on an interval $-d/2<x<d/2$ where in general solutions are of form $\sin(n\pi x/d)$ for even and $\cos(n\pi x/d)$ for odd. Could i then rightfully say that i have states 7 and 4 on an interval $-d/2<x<d/2$?