Advanced Quantum Mechanics Lecture 3
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- Опубликовано: 22 май 2024
- (October 7, 2013) Leonard Susskind derives the energy levels of electrons in an atom using the quantum mechanics of angular momentum, and then moves on to describe the quantum mechanics of the harmonic oscillator.
Originally presented by the Stanford Continuing Studies Program.
Stanford University:
www.stanford.edu/
Continuing Studies Program:
csp.stanford.edu/
Stanford University Channel on RUclips:
/ stanford
I dozed off last night. Guess what? I woke up finding myself playing Advanced Quantum mechanics lecture the whole night. lol
Lmao this happened to me too 😂
Same
Me too.... just woke up thinking what the hell
this is literally me too lol, just woke up and this was on
I hope this means I will retain this information
I went to bed watching Ice Cream Sandwich talking about which video game item he wanted in real life, why did I wake up to this
... I fell asleep and autoplay dragged me here.
I love the way he derives these highly formal results using so little. In standard texts and lectures we'd be up to our ears in Shrodinger equations, polar co-ordinate wave functions and the experimental methodology. - But here he just uses a few simple definitions from QM theory written on the back of a napkin - and see how far he goes with it! A real masterclass in deductive reasoning.
I think the key difference is why you want to know. Experimental results are critical for the progress of actual physics, but if all you want to do is understand the physics that others deduce it is not as important. Rigor is needed for physics in practice, but not to get across the key concepts to a lay audience.
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9a9
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Ooo😅😅😅
Mike Ehrmantraut is one top shelf physicist.
Put yo' spin away Walta'! I'm not teaching QM to you.
1:18:00 - I'll throw this in, since Dr. S. didn't underscore this point very explicitly. That "+1" in L*(L+1) is there because of Heisenberg uncertainty. If you could measure Lz and L^2 and found them to be equal, then you would know that Lx = Ly = 0. You'd know all three components of angular momentum, and that's not allowed. L^2 = Lz^2 + L, and that L is partitioned between Lx and Ly in an uncertain way. That maintains HUP. :-). Cheers, guys - happy learning!
Thanks
Really clears it up
💔💔💔💔
Excellent explanation!
I rlly woke up to me listening to this and i havemt even study this yet
wtf same lmao
Yep same for me
Some how this video came on while I was sleeping. Decided to try and watch it and see what I understood…. Now I feel stupid.
I fell asleep and this turned on .gained knowledge
We finally get to the quantum harmonic oscillator!
I am an Arts student of 17 but i loved physics
I was watching ghost adventures, how did i wake up to this 😮😂
Part 1 of lecture pertains to angular momentum states of electrons in an atom. This is beautifully explained by the Professor.
Part 2 (@1:24:48) pertains to the Harmonic Oscillator. This part was left from the Basic QM course and hence is being covered here.
Sizhoi/Okuma ostshfbu
🌟
Does anyone else wake up on these randomly? Why youtube is forcing me quantum knowledge while I sleep.
I'm drunk. When I'm sober, I'll consider if this made any more sense.
I have no idea how I ended up here, and I have no clue what he’s talking about cause I’m in the medical field, but I’m enjoying him talk lol
Angular momentum and spherical harmonics; Central force 32:00; Harmonic Oscillator 1:24:00
Nbn
Thanks so much 🌟
I fell afsleep to "10 soccer goals you'll never see again" and woke up to this
HAHA!!
My goodness. This was playing while I slept. That was a confusing dream.
🤣🤣🤣🤣
dude i just woke up where am i
This guy literally stuffed half a scone into his face in the midst of giving an advanced QM lecture that he knew would go to RUclips for thousands of people to see. He is the best.
Sidney Coleman used to smoke cigarettes in the middle of recorded lectures at Harvard.
❤Thank you very much professor and class
Gegenbauer polynomials appear to be part of a mathematical hellscape where only those who can breathe the rarified air of high mathematics can survive. 😁
@25:00 Highest state (l) is like state rotating about z axes where all Angular momentum is in vertical (z) direction.Every other states (m: magnetic quantum number) in the same multiplexer has the same value of L^2 = l(l+1) and comes in integer multiples (because in QM it is quantum quantized projection on the z axes of arbitrary direction angular momentum).
Second half of this lecture is about harmonic oscillator and ladder operator a+a-.
0h yeah, well I like GIRLS ! So ......therethen
Because I could not find the notes of these lectures, I made my own in MS Word. I have made them available both in pdf format (@t and in MS word format (@t. Feel free to use them as starting point for your own notes of this terrific series of lectures.
Link?
@@shadmanshakib1425 yes :-) 🌟
What am I doing here? I just forgot to turn off my PC with youtube on before I went to bed.
1:17:30 - L*(L+1) is very nearly L^2 for classical entities - L is huge in that case and the difference negligible. That's the uncertainty principle in play. If you know (Lz)^2 = L^2, you can't have L^2 = (little L)^2 because that would mean Lx and Ly had to be zero. You'd know all three, violating uncertainty principle. That extra (little L) angular momentum is distributed in an unpredictable way across Lx and Ly, to satisfy Heisenberg.
Don't want to make Heisenberg angry
@@AkamiChannel oo
Vvo
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Vv Vivo vvvoooo va pasando porque por lo en ooov de que me hablas en camino que está pasando 😃 cc 😃v😂 popote y para por eso v
i LOVE THIS GUY
Why do i always wake up to these videos totally unrelated with the 1st when i let them roll
I’m admittedly pretty much of an idiot compared to anyone who understands all of this, so I just put this on to go to sleep to.
same ;-;
There used to be a download option. Was that taken away or can I just not see it?
Bro why do I keep falling asleep to these type of videos?
amazing
This stuff has really turned me on. At 63, I've fallen in love with quantum mechanics.
Better late then never
Wow
Really dude? I need smelling salts after this.
Sorry to hear, try a woman?
@@aeroscience9834
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I could be gaming but this is more fun
Please, how to prove: N a^{-} |n> = (n-1) a^{-} |n> ???
I am nowhere near this level in physics, i have no idea how this got recommended to me.
What would Dirac do? He would commute :)
That cracked me up too. ;)
Bro I fall asleep watching yt and this turns on 😭😭😭
I'm really perplexed by the fact that this is "Advanced" QM yet the class is just now being introduced to the quantum harmonic oscillator.
The first intro course is basically the first half of Sakuri and the second advanced course is basically the second half of Sakuri.
And there's only 10 lectures in these courses, so really each course is only 5 weeks. At stanford a typical quarter is 10 weeks so it's basically just 1 standard 10 week course on QM following Sakuri + Susskind's personal spin on the subject.
I have not watched the basic QM course but understod from the comments that by mistake they did not cover the harmonic oscillator which is important for understanding subsequent concepts. Therefore it is covered here in detail. When I took QM long ago it was one of the first subjects.
26:08 to 26:25 tension resolved 😅
Are gegenbauer polynomials the same thing as legendre polynomials in this case?
No
how do you define awkward in quantum mech.?
...at 73 years old is reasonable feel tired....so rest..
Mistake? 54:11 Radial momentum operator is Pr = id/dr + i/r ????? 😮😮
I woke up to this video.
How RUclips got from an "At the mountains of madness" audiobook to this IDK.
Im at work zoned out working and didn't realize I'm learning advanced quantum physics
Do any one know which book is being followed through out all of this lecture
You can consult his book "Quantum Mechanics: The Theoretical Minimum". It pertains to the initial QM lecture series by Prof. Susskind.
The Theoretical Minimum series of books (there are currently 3) is based on these lectures. I highly recommend them. I wish I'd found the lectures and watched along as I went through the books.
But If I apply L square = Lz^2 + Lz + L-L+ to |l-1> directly, this will result in L^2-L+1 not L(L+1) ?
I was wondering exactly that :(
you commute L_ from left side of L^2 to right side. then L_ operates on | l > giving |l-1>. Since [L^2, L_] = 0 no additional factors are needed when using communitive property so the original equation L^2| l > = l(l+1) | l > is maintained except now | l > is replace with | l -1 > . If u pull out the L_ and replace it with Lx-iLy then distribute it u have to do it to L^2 on the left side as well so it is no longer L^2 = .....
It’s because L-L+|l-1> is not equal to |l-1> but rather a constant times |l-1> (since it was only pointed out that L+|m> is only equal to an eigenvector of |m+1>, so L+|m> is actually equal to a|m+1> where a is constant. You can find what the derivation for the value of “a” is in the “Ladder Operator” page of Wikipedia)
Standing in the shadows of Love 💕
“Many of those who sleep in the dust of the earth will awake, some to eternal life, and some to shame and eternal contempt. Those who are wise will shine like the bright expanse of the heavens, and those who lead many to righteousness, like the stars forever and ever.”
Daniel 12:2-3
Why do religious retards spread this crap on a highly educated (not stupid) scientific audience...?
🌟 Appreciate the reviews 🙌🏼➰💭 1:51
1:40 WWDD? Delightful!
I only understand the 1st 5 minutes of any of his lectures!
Read zettili or Griffith and you survive .
at 1 hour 38 minutes you should give the names of yes and no.
Why do we even talk about angular momentum in quantum mechanics? What we are talking about is a quantity that has some similarities with classical angular momentum but it also has many important differences. For example, in the ground state in quantum mechanics, angular momentum is zero. However, due to the Uncertainty Principle, this doesn't mean that all motion ceases. A particle in the ground state will continue to exhibit random motion even though it has no angular momentum. This example alone illustrates how calling this quantity angular momentum is nonsensical. It is equivalent to referring to your cat as being a dog purely on the basis that it has four legs and a tail.
First of all, there is no particle exhibiting random motion. You should only talk about what you can observe. In classical mechanics, angular momentum is r*p but you can not measure both r & p simultaneously in quantum mechanics. But that doesn't mean we can't use classical terminology since it does behave like angular momentum in various sense of the term, the primary of which is it's correspondence with rotational symmetry (if you are familiar with Noether's theorem, you would understand what I mean here). As far as measurement go, you can measure angular momentum indirectly by applying magnetic field and noting the energy of the electron.
The apparent ability to measure classical angular momentum accurately is due to the fact that the classical equations are mere approximations. In reality there will always be uncertainty in measurements but these are not considered in classical mechanics. Moreover since [L,H]=0 it means that quantum angular momentum is a conserved quantity just like classical angular momentum.
Is it always the case that a constructor and destructor will be Hermitian conjugates?
yes because the quadratic (in both position and momentum) harmonic oscillator hamiltonian X^2+P^2 (ignoring constants) is factorized into (X+iP)(X-iP) and these two factors are the creation and destruction operators (with the constants present now)..those two factors are mutually related through the replacement (i) --> (-i) so are Hermitian adjoints (generalization of conjugates of square matrices to possibly infinite dimensional matrix case in Hilbert space)..
Is that ARrrrr of Van Sants ?
what sense does it make if we compare the HO energy of classic with QM? NONSENSE! what happens to Correspondence Principle?
Even the order of release is quantic....
You need to learn Quantum Mechanics Waltuh
Put yo' spin away Waltuh! I'm not teaching QM to you.
Why was this in my reccomended I'm 13... im in 7th grade why am I here
You could be the next Einstein.
@@tedschroeders5289 true to that
These are all my RUclips hours
Sir do you teach today also
Mike from breaking bad?
Ah yes of course 🍷
Wow
This is well beyond me
Mathematics is the key to understanding anything in this universe. Without mathematics you might as well go read Shakespeare plays!
I think that they both have their place. Yes, to rigorously understand anything in the material universe, you need mathematics. But if you do math for 12 hours per day without a break every now and then to enjoy the lighter topics, you'll loose your mind in time.
You may not understand Shakespeare if you are not aware of the basic ideas of mathematics.
@MrComrade True :)
Susskind forgets the qb4 quantum resistance factor multiplied by the electron flux initiator which cancels out random proton momentum.
That's the first thing I noticed too.
someone does not understand the physics making fool of teachers; i love all lecture
Here is Motorola on roaming and wifi and sim cards and physical storage and cloud storage and it works just fine and I don't use a ground home phone cable it mutated on its own to survive
I am doing a research project. Are any of the commenters here African American? Thank you.
I learned all this stuff in the 4th grade.
My literal parent like the psychology study like monkeys it obeys me because I'm trying to fucking save it
I'll
õتزت تأا ظ
Wtf I was listening to tinder lines by fakejake and then I hear this stuff? Literally no coralation RUclips, go home you drunk at lol
This is my parent you tried to kill
A small quantum adjustment is like a little yeast it makes the whole theory rise, the corollary to the rule is that the faith of a mustard seed grows into a tree that the birds nest. So keep trying professor, because you will see something new that you have not known nor has any eye seen, nor has any ear have heard what God has in store for those who love him and are called according to his purpose. Yahweh will lift up whom he will and put abase whom he will. Try this calculation The Aleph and the Tau and forget the greek interpretations.
There is nothing ‘advanced’ about this.
Why?
This sucks