7 ms·

I've been on a personal quest to understand quantum electrodynamics and perhaps quantum chromodynamics. It is quite daunting as my formal math education pretty

I've been on a personal quest to understand quantum electrodynamics and perhaps quantum chromodynamics. It is quite daunting as my formal math education pretty much stopped at linear algebra. I'm currently going through one of MIT's 8.04 (Quantum Physics 1) through OpenCourseWare and it's been pretty accessible so far. The jump from classical quantum mechanics to quantum field theory, however, seems pretty large and out of reach of anyone who doesn't want to spend a LOT of time studying pure math. In other words, I look forward to being able to enjoy these in about 3 years ;)

sungam 6y ago
If you have not already read it I would highly recommend Feynman's QED: The strange nature of light and matter - I am certainly not a mathematician or physicist but Feynman has a genius for communicating to the layman at a level that facilitates intuition about how a system behaves
ShinyRice 6y ago
I don't understand why you're getting snagged up on in QFT, I've recently done a course on that and it wasn't that complicated, though that's if and only if you've studied or at least understood the algebra of creation and destruction operators found in the quantum harmonic oscillator, and classical field theory. I didn't have a course on classical field theory, but I did have a chapter of a course dedicated to it. In terms of math, I've only encountered linear algebra, multivariable calculus with A LOT of Dirac deltas and a smidge of complex analysis, necessary to calculate the Feynman propagator.
- jiggawatts 6y ago
  My problem with QED/QFT is that it gets about five levels of abstraction too far from physical intuition and then really starts layering on the algebra. At the end, it's totally abstract and I very strongly suspect (but cannot prove) that nobody knows what it all means in the end. My current pet project is to try and write a "renderer" that uses QED, or better yet, some more advanced subset of the Standard Model instead of the oversimplified "raycasting" model typically used in computer graphics. I'd be happy with a "quantum" Cornell Box, ideally in a fully relativistic model that can simulate the speed of light, diffraction, interference, etc... I'm trying to see how far modern physics has gone and still be in contact with a fully general, numerical, real theory. Not just the abstract properties of statistical theories, if you know what I mean. So far it hasn't been a fruitful journey, I can't even find a reasonable description of an electron's U(1) field equation as described by QED. I get that it has a bunch of properties such as its symmetries, transformations, etc... but this is like the description of an elephant by a blind man touching each part.
  - ShinyRice 6y ago
    Maybe you should start with understanding non relativistic quantum mechanics before understanding QFT. QFT's only a small jump from QM, more or less. As well as understanding classical field theory and Noether's theorem. There are some ad hoc things done seemingly at random, like having to add terms to a Lagrangian to make it invariant under U(1) transformations, and that may seem weird at first, but it's those leaps of faith that got us to where we are.
    - perl4ever 6y ago
      I agree with a lot of people that Feynman's descriptions of physics are appealing but I tend to feel (although it could be just me) that it's more about making you feel like it's intuitive than really transferring his intuition to you. It's sort of like you go skydiving for the first time, and you go on a tandem jump where you're strapped to the instructor, and it's an amazing experience, but you didn't really do anything. Or you ride on the back of a motorcycle, etc... But Feynman's explanations give me the tantalizing feeling that something even better is possible. One general direction I can imagine is that I suspect a truly intuitive understanding would start with more general math describing any quantum theory and avoid specifics at first that relate to real world physics. Unfortunately, mathematicians are addicted to using named of other mathematicians as shorthand (as you do in your short comment) and I think that's a sign of where things go haywire for a layperson. As long as you're dropping names, you are on the wrong track as far as explaining goes. Feynman had a much quoted comment that's associated in my mind, about how when you just know the name of something, you know nothing about it.
  - yummypaint 6y ago
    I reccommend also doing some reading about foundational lattice field theory concepts in parallel with classic QFT. Comparing and contrasting the two can help with understanding both. Maybe start with ultraviolet divergence? Lattice based theories have also been more successful as far as making good predictions. I think it appeals to intuition that people who write software may find more familiar.
    - 6y ago
yummypaint 6y ago
I dont usually recommend textbooks, but Griffiths QED may be of interest if you haven'thheard of it. PDFs abound.
- Rerarom 6y ago
  You mean the elementary particles book?
  - yummypaint 6y ago
    Sorry that was clear as mud. This is what i was remembering: isbn 978-0131118928. In grad school i frequently used Griffiths as a solid jumping off point for more challenging resources.
    - Rerarom 6y ago
      Thanks! So the QM book.
Koshkin 6y ago
Susskind’s Stanford videos are a treasure trove. While not shunning the math, the lectures are extremely accessible.
- jiggawatts 6y ago
  I've struggled to watch more than a few hours. He might be brilliant, but his presentation style is atrocious. He gets distracted, forgets things, etc... Feynman's lectures in comparison are much more focused and sharp.
- pickdenis 6y ago
  I'm currently watching his General Relativity videos along with the MIT stuff. There's a really good explanation of vector co(ntra)variance and tensor algebra at the beginning of that course which I needed. And contrary to the sibling, I really enjoy his presentation style which assumes that I am not a graduate student in math who lives and breathes abstract algebra.
tobmlt 6y ago
In case it’s helpful, I’ll plug Richard Mattuck’s “a guide to Feynman diagrams in the many body problem” here. This book takes the magic out of Feynman diagrams for sure.

sungam 6y ago

If you have not already read it I would highly recommend Feynman's QED: The strange nature of light and matter - I am certainly not a mathematician or physicist but Feynman has a genius for communicating to the layman at a level that facilitates intuition about how a system behaves

ShinyRice 6y ago

I don't understand why you're getting snagged up on in QFT, I've recently done a course on that and it wasn't that complicated, though that's if and only if you've studied or at least understood the algebra of creation and destruction operators found in the quantum harmonic oscillator, and classical field theory. I didn't have a course on classical field theory, but I did have a chapter of a course dedicated to it. In terms of math, I've only encountered linear algebra, multivariable calculus with A LOT of Dirac deltas and a smidge of complex analysis, necessary to calculate the Feynman propagator.

jiggawatts 6y ago
My problem with QED/QFT is that it gets about five levels of abstraction too far from physical intuition and then really starts layering on the algebra. At the end, it's totally abstract and I very strongly suspect (but cannot prove) that nobody knows what it all means in the end. My current pet project is to try and write a "renderer" that uses QED, or better yet, some more advanced subset of the Standard Model instead of the oversimplified "raycasting" model typically used in computer graphics. I'd be happy with a "quantum" Cornell Box, ideally in a fully relativistic model that can simulate the speed of light, diffraction, interference, etc... I'm trying to see how far modern physics has gone and still be in contact with a fully general, numerical, real theory. Not just the abstract properties of statistical theories, if you know what I mean. So far it hasn't been a fruitful journey, I can't even find a reasonable description of an electron's U(1) field equation as described by QED. I get that it has a bunch of properties such as its symmetries, transformations, etc... but this is like the description of an elephant by a blind man touching each part.
- ShinyRice 6y ago
  Maybe you should start with understanding non relativistic quantum mechanics before understanding QFT. QFT's only a small jump from QM, more or less. As well as understanding classical field theory and Noether's theorem. There are some ad hoc things done seemingly at random, like having to add terms to a Lagrangian to make it invariant under U(1) transformations, and that may seem weird at first, but it's those leaps of faith that got us to where we are.
  - perl4ever 6y ago
    I agree with a lot of people that Feynman's descriptions of physics are appealing but I tend to feel (although it could be just me) that it's more about making you feel like it's intuitive than really transferring his intuition to you. It's sort of like you go skydiving for the first time, and you go on a tandem jump where you're strapped to the instructor, and it's an amazing experience, but you didn't really do anything. Or you ride on the back of a motorcycle, etc... But Feynman's explanations give me the tantalizing feeling that something even better is possible. One general direction I can imagine is that I suspect a truly intuitive understanding would start with more general math describing any quantum theory and avoid specifics at first that relate to real world physics. Unfortunately, mathematicians are addicted to using named of other mathematicians as shorthand (as you do in your short comment) and I think that's a sign of where things go haywire for a layperson. As long as you're dropping names, you are on the wrong track as far as explaining goes. Feynman had a much quoted comment that's associated in my mind, about how when you just know the name of something, you know nothing about it.
- yummypaint 6y ago
  I reccommend also doing some reading about foundational lattice field theory concepts in parallel with classic QFT. Comparing and contrasting the two can help with understanding both. Maybe start with ultraviolet divergence? Lattice based theories have also been more successful as far as making good predictions. I think it appeals to intuition that people who write software may find more familiar.
  - 6y ago

yummypaint 6y ago

I dont usually recommend textbooks, but Griffiths QED may be of interest if you haven'thheard of it. PDFs abound.

Rerarom 6y ago
You mean the elementary particles book?
- yummypaint 6y ago
  Sorry that was clear as mud. This is what i was remembering: isbn 978-0131118928. In grad school i frequently used Griffiths as a solid jumping off point for more challenging resources.
  - Rerarom 6y ago
    Thanks! So the QM book.

Koshkin 6y ago

Susskind’s Stanford videos are a treasure trove. While not shunning the math, the lectures are extremely accessible.

jiggawatts 6y ago
I've struggled to watch more than a few hours. He might be brilliant, but his presentation style is atrocious. He gets distracted, forgets things, etc... Feynman's lectures in comparison are much more focused and sharp.
pickdenis 6y ago
I'm currently watching his General Relativity videos along with the MIT stuff. There's a really good explanation of vector co(ntra)variance and tensor algebra at the beginning of that course which I needed. And contrary to the sibling, I really enjoy his presentation style which assumes that I am not a graduate student in math who lives and breathes abstract algebra.

tobmlt 6y ago

In case it’s helpful, I’ll plug Richard Mattuck’s “a guide to Feynman diagrams in the many body problem” here. This book takes the magic out of Feynman diagrams for sure.