Fermions and Bosons; Pauli exclusion principle 13:00; Spin 31:30; Rotaion by 2 Pi simmetry 40:00; Proving the basic symmetry of the world is rotation by 4 Pi 51:00; Rotation 2 Pi Plus exchange is Identity 57:00; Experiments on rotation and interference 1:18:00;
Magical Physics , Shown by Magician No.1 Physicist Susskind at 51:51. For me the whole lecture after that till last second was mesmerising and magical Quantum Mechanics.
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.
0:38:30 if Wikipedia is correct: "According to Dirac, it was first studied by Fermi, and Dirac called it Fermi statistics and the corresponding particles Fermions."
Lmao he referred to Gerard T'Hooft as a circus performer. I wonder if he ever actually was in the circus or if Susskind is just poking fun at him since they're friends. But for those who don't know, Gerard T'Hooft is a nobel prize winning theoretical physicist.
Wouldn't sending any charge, including one as small as an electron, through a solenoid cause a fluctuation of the magnetic field? If so, why wouldn't that be considered an observation?
Here's what I don't understand. He's making a claim about QM symmetry with the 2pi vs 4pi rotation for bosons and fermions, which is ultimately traced back to the magnetic quantum number. But the belt or the Dirac box arguments seem to hold for anything, not just QM. What do I have wrong?
Also, the maths that is behind the belt and the Dirac box is really the same maths that makes this spin 1/2 phenomenon with the magnetic quantum number happen in the first place (in a hidden way). It is all connected in a more-or-less convoluted way to the theory of Lie groups, which studies continuous symmetries of stuff. The statement he makes that doing one twist in 3D is not the identity but doing it twice is can be phrased mathematically by saying that \pi_1(SO(3)) = Z/2. If you'll excuse my jargon, we can then take the double (universal) cover of SO(3) which is called Spin(3) and turns out to be equal to SU(2), and this last group is the "true" symmetry group of the single electron system. To know more you can google things like "spinor" or "spin representation" or even "special orthogonal group" (SO(n)), "spin group" (Spin(n)) or "special unitary group" (SU(n)). This book up to chapter 7 gives a nice account of how everything fits together in a rigorous way, if you have the motivation to understand the mathematical formalism needed: www.math.columbia.edu/~woit/qmbook.pdf
Consider it this way: 1/2 spin of an electron makes 1/2 wave in 2π rotation. This means that after 2π rotation the particle is exactly opposite to its state when it was at 0 rotation. This is certainly true for classical physics and it is true for QM too.
@26:40, If particle is indistinguishable, then Ψ0(x1) should equal Ψ0(x2). Why did he say that Ψ0(x1)Ψ1(x2) not equal to Ψ0(x2)Ψ1(x1)?? Before @35:00 I think the explanation about boson&fermion in Pauli exclusive state is reluctantly and unclearly!
Because Ψ is not the whole story. The observed probability is given by Ψ*Ψ, not by Ψ alone. (Go back to the very end of lecture 4 where he explains about the 'swap' operator). There are two options for the sign of Ψ so Ψ0(x1)Ψ1(x2) can be equal to plus or minus Ψ0(x2)Ψ1(x1).
At about 20:00, the professor explains that an exchange of position can lead to a phase change of exp(i * phi). But what if phi is a function of x1 and x2, e.g. phi = x1 - x2? This will automatically make two consecutive exchanges equal to 1.
if it is consistent to make phi a function of x, then this is a valid question :) But you have to think about what to do with differential operators like momentum then - they would pick up extra terms from the derivative of exp(i phi). Solving this carefully leads to gauge theories and is an essential part of the standard model.
Fermions and Bosons; Pauli exclusion principle 13:00; Spin 31:30; Rotaion by 2 Pi simmetry 40:00; Proving the basic symmetry of the world is rotation by 4 Pi 51:00; Rotation 2 Pi Plus exchange is Identity 57:00; Experiments on rotation and interference 1:18:00;
Lllll ki
lol lllllllllllll IMO lllehet ok llll lol loll ok llllllllll pool lll lol ll lol l lol ok llllllllllllllllll lol llllllllllllllllll
❤thank you very much
Many thanks
Magical Physics , Shown by Magician No.1 Physicist Susskind at 51:51. For me the whole lecture after that till last second was mesmerising and magical Quantum Mechanics.
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.
Dear hubert, Where can I find your notes?
This stuff around 1:00:00 - on belts, solitons, spin-statistics, etc.- this is fascinating, and important, I think.
0:38:30 if Wikipedia is correct:
"According to Dirac, it was first studied by Fermi, and Dirac called it
Fermi statistics and the corresponding particles Fermions."
0:38:55 Girgio have a look at Wikipedia "Fermi-Dirac statistics" footnote 5
Rotating coffee cup 4 pi
MIND=BLOWN
m.c.rapsavier firetrucks firetrucks what color are those red firetrucks"""""familyguy
❤thank you very much Professor and class
Lmao he referred to Gerard T'Hooft as a circus performer. I wonder if he ever actually was in the circus or if Susskind is just poking fun at him since they're friends. But for those who don't know, Gerard T'Hooft is a nobel prize winning theoretical physicist.
I think he's a circus performer because he'll start spinning coffee cups above his head in the middle of physics discussions
F. Cf
G cx
G cx
Cyyfcct yc
a million years lets see that's a monday right
Is there an intuitive reason why the spin or helicity of a boson dictates whether it mediates attractive(gravity) or repulsive(like charges) forces?
Are photons considered solitons? Would this imply the 1/2 spin topology for light? How would a wave be integer spin topology instead?
Funny and great lecturer!
Wouldn't sending any charge, including one as small as an electron, through a solenoid cause a fluctuation of the magnetic field? If so, why wouldn't that be considered an observation?
where can i find recommended books?
sakurai, cohen-tanuji
oded basis thanks
So basically bosons are well-behaved particles and fermions are bad guys.
Can we make an equivalent demonstration as in 1:03:00 using a Mobius Band ?
Here's what I don't understand. He's making a claim about QM symmetry with the 2pi vs 4pi rotation for bosons and fermions, which is ultimately traced back to the magnetic quantum number. But the belt or the Dirac box arguments seem to hold for anything, not just QM. What do I have wrong?
Also, the maths that is behind the belt and the Dirac box is really the same maths that makes this spin 1/2 phenomenon with the magnetic quantum number happen in the first place (in a hidden way). It is all connected in a more-or-less convoluted way to the theory of Lie groups, which studies continuous symmetries of stuff. The statement he makes that doing one twist in 3D is not the identity but doing it twice is can be phrased mathematically by saying that \pi_1(SO(3)) = Z/2. If you'll excuse my jargon, we can then take the double (universal) cover of SO(3) which is called Spin(3) and turns out to be equal to SU(2), and this last group is the "true" symmetry group of the single electron system. To know more you can google things like "spinor" or "spin representation" or even "special orthogonal group" (SO(n)), "spin group" (Spin(n)) or "special unitary group" (SU(n)). This book up to chapter 7 gives a nice account of how everything fits together in a rigorous way, if you have the motivation to understand the mathematical formalism needed: www.math.columbia.edu/~woit/qmbook.pdf
Consider it this way: 1/2 spin of an electron makes 1/2 wave in 2π rotation. This means that after 2π rotation the particle is exactly opposite to its state when it was at 0 rotation. This is certainly true for classical physics and it is true for QM too.
@@hasanshirazi9535 lol- ya, I wish the students would have let him finished to make this point.
@26:40, If particle is indistinguishable, then Ψ0(x1) should equal Ψ0(x2). Why did he say that Ψ0(x1)Ψ1(x2) not equal to Ψ0(x2)Ψ1(x1)??
Before @35:00 I think the explanation about boson&fermion in Pauli exclusive state is reluctantly and unclearly!
Because Ψ is not the whole story. The observed probability is given by Ψ*Ψ, not by Ψ alone. (Go back to the very end of lecture 4 where he explains about the 'swap' operator). There are two options for the sign of Ψ so Ψ0(x1)Ψ1(x2) can be equal to plus or minus Ψ0(x2)Ψ1(x1).
11:00 How about the Majorana fermions? Don't they violate the Pauli's exclusion principle?
the generator "jay-z" 46:35
lol you and me both
can you please kindly add subtitles?
At about 20:00, the professor explains that an exchange of position can lead to a phase change of exp(i * phi).
But what if phi is a function of x1 and x2, e.g. phi = x1 - x2? This will automatically make two consecutive exchanges equal to 1.
phi is an angle about the origin; i.e. a variable. It is not a function itself.
if it is consistent to make phi a function of x, then this is a valid question :)
But you have to think about what to do with differential operators like momentum then - they would pick up extra terms from the derivative of exp(i phi). Solving this carefully leads to gauge theories and is an essential part of the standard model.
Yup. I posed the question 8 years ago. Since then I have learned QFT.@@deinauge7894
A great example of swapping en rotating can be seen in this short video:
ruclips.net/video/Nat-EsReXtQ/видео.html