Lecture 3: Why Quantum Field Theory
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- Опубліковано 6 жов 2024
- MIT 8.323 Relativistic Quantum Field Theory I, Spring 2023
Instructor: Hong Liu
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Inadequacy of relativistic quantum mechanics, unification of quantum mechanics with special relativity requires quantum field theory, field theory as a continuum description of discrete systems, review of quantization of harmonic oscillator in the Heisenberg picture
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Chap 1 (contd.)
00:00:25 Difficulties with Rel. QM
00:13:14 Continuum limit of 1D chain of particles
00:25:00 Summary (Why QFT?)
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00:26:48 Plan for the course
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Chap 2 - Free Scalar Field Theory
00:34:05 Quantization of Harmonic Oscillator (Heisenberg Picture)
00:43:12 Summary - Steps of quantization
00:49:41 Classical solutions of the KG field equation
00:57:02 Quantization of the Free Scalar Field
Another great lecture, thank You!
The recaps of fairly basic qm koncepts makes partially forgotten stuff resurface again instead of one getting stuck...making it much easier to follow the lectures. Excellent pedagogic skill.
Absolutely!
These are way better explanations than the books i've read so far.
Although I am far from MIT, I have gained immense knowledge from these outstanding and comprehensive lectures. The fact that all of these resources are available for free is truly remarkable. While studying these lectures, I feel as if I am present in an MIT classroom. Thank you for uploading such exceptional courses.
Best Regards,
Syed Siraj
I'm confused at 41.27. If p(t) is dx/dt, then I can work out p(t) in terms of a and a+ using eqn (xx). I then plug this in to the commutator equation [x,p]=i. However I then get [a,a+]=1/w (where w is omega)
43:12
59:12
ryan mathematics
helen geometry
david algebra
andrew combinatorics
samuel analysis
peter internet
Everyone dies.
Can't we send information back in time to prevent a tragic death?
Or can't we send a message to the future and ask them to tell you how to do it?
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Please, Can you make it possible to sending messages to past?
My father Kim Kyu Dong died SNU hospital at 2024.04.15.
I must prevent that death.
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Both light and electromagnetic waves are called waves.
Is the wave going out from point A to point B?
Or is it already at points A and B like the sea, but only the waves are transmitted?
In modern science, it seems to be seen as the former...
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What about time and space?
In modern science, time and space are the latter, don't you think?
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In other words, space-time comes first, and light, photons and protons go along that path...
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So the Einsteinian school's absolute speed of light is strange?
At the absolute speed of light, is not the speed determined by light, but by the time and space that already exists?
Isn't speed the time to move from point A to point B?
If time and space are not absolutely fixed, why does the speed of light have absolute speed?
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Therefore, the absolute speed of light can also be wrong.
Isn't the absolute speed of light a space-time dimensional barrier?
If it exceeds the absolute speed, will it jump to another dimension?
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Einstein's theory is based on the dimension only now, so if you go beyond this dimension, is not it beyond the constraints of Einstein?
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The question is whether you can find an object faster than light or accelerate light.
Or is space-time and massive mass spread out in front of us, and can not we cross the space-time dimension using space-time and massive mass?
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In this sense, I think we should study whether there is a way to send signals to the past.
You don't have to worry about who in the past will get this signal, do you?
We're already receiving a 24-hour signal from radio telescopes and various receivers.
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If we go deeper...
Light has a slower speed as it passes through the medium.
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It is not that we can not accelerate light, but is not the absolute speed of light the highest speed of light observed in our dimension?
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Is not it observable only at a constant speed in the dimension we are in?
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If we accelerated the light at all, for example, if we shot light on a spacecraft, or if the light of the sun already moving at a high speed exceeded the observable absolute speed, would not it have passed to another dimension?
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Whether there are eleven dimensions, or even larger dimensions, is not there necessarily a overlap with our dimension in the end?
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Would not light or radio waves that went to another dimension come back to our dimension as slow as passing through the medium?
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Can't we do an experiment like this?
No you can't
@@brattok Then please find another way to change past... I have to save my father.
Please present lectures for more than just college kids who've missed their classes. In 15 years someone watching won't know what you taught in last lecture. They might be coming at it fresh. Be like Feynman, he was famous because his reach was massive. My grandma could watch any of his lectures and still learn everything.
We don't have recordings of Feynman's professional lectures for all I know.
There is no easy way around the background required for these courses. If you want to seriously learn qft then you must seriously study the prerequisites. If he were to start from the beginning, this lecture series would be 10000 hours long
@@MegaAvinator Good guess. K-12 + undergrad equals roughly 15,000 hours of learning. Maybe a little over 20,000 for those who are extremely studious. :-)
You know what, though? An AI can be trained to know a hundred times, if not a thousand times more in a month or so. That's just an LLM that can't reason with that knowledge, yet, of course... but just imagine somebody manages to connect that LLM to an actual reasoning model. Now you got a problem. ;-)
This is a second year graduate course on quantum field theory. Of course it needs a technical background.
@@sheldonrego6121 Yes, it needs undergrad physics, which is two years, three at most.