Learn QCD & QED: What you need know

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    Qcd Qed
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Discussion Overview

The discussion centers around the prerequisites and resources necessary for learning Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED). Participants explore various foundational subjects, recommended readings, and the importance of understanding complex mathematical concepts in the context of theoretical physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants suggest that to learn QED and QCD, one must understand Classical Field Theory, Classical Electrodynamics, Relativity, Group Theory, and both Relativistic and Non-Relativistic Quantum Mechanics, along with introductory Quantum Field Theory.
  • Ryan emphasizes that while recommended books like Feynman's QED can provide intuition, they may not equip learners to tackle complex problems without a solid foundation in the necessary subjects.
  • Hans shares a resource from Gerard 't Hooft, outlining a comprehensive list of topics for aspiring theoretical physicists.
  • Multiple participants express confusion regarding Group Theory, with some seeking clarification on its applications in physics and its mathematical complexities.
  • Marlon argues that understanding subjects like Group Theory and Differential Geometry requires more than online resources, advocating for formal education and textbooks to grasp the physical implications of these concepts.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of a strong foundational knowledge in various subjects to study QED and QCD. However, there is disagreement on the adequacy of online resources for learning complex topics like Group Theory, with some advocating for traditional educational methods.

Contextual Notes

Some participants note that the mathematical formalism presented in online resources may not provide the intuitive understanding needed for application in physics, highlighting a potential gap in self-study approaches.

michealsmith
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wat do u need to learn to learn qcd and qed
 
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Ok ok ok, here are the Feynman lectures, highly recommended from just about anybody:



Audio:

And QED, a really short paperback by Feynman:
 
If you really want to learn QED and QCD you will need:

Classical Field Theory
Classical Electrodynamics
Relativity
Group Theory
Relativistic and Non-Relativistic Quantum Mechanics
Introductory Quantum Field Theory
(and all the physics to be able to do the above listed subjects)

The books that MK listed are good (actually great if you already know the material) and QED by Feynman will give you and intuitive notion of the subject, but if I gave you the QED lagrangian and asked you to work out a cross section for a scattering event, you will have no clue what to do.
Good luck with your studies.
Cheers,
Ryan
 
michealsmith said:
wat do u need to learn to learn qcd and qed

Here's the whole list as advised by Nobel laureate Gerard 't Hooft.
Most of it applies if you want to go all the way to QCD.

HOW to BECOME a GOOD THEORETICAL PHYSICIST:

http://www.phys.uu.nl/~thooft/theorist.html


Regards, Hans
 
Hans, that's an excellent site. Lots of good tutorials, thank you!
 
Norman said:
If you really want to learn QED and QCD you will need:

Classical Field Theory
Classical Electrodynamics
Relativity
Group Theory
Relativistic and Non-Relativistic Quantum Mechanics
Introductory Quantum Field Theory

What is group theory?
I looked it up and at first it seemed like another way of manipulating numbers, like matrices or tensors, but then they got into 'classifications of geometry' and permutations and now I'm totally confused.
 
tashi said:
What is group theory?
I looked it up and at first it seemed like another way of manipulating numbers, like matrices or tensors, but then they got into 'classifications of geometry' and permutations and now I'm totally confused.
The example of the rotation group may help you to understand it.
 
good sites ..thanks
 
  • #10
At the risk of sounding like some old fashioned dude i would like to say that subjects like group theory, differential geometry, etc cannot be learned from looking at websites. For example, although the mathworld site is a reliable source it is far from introductory. This site gives the complete mathematical formalism behind the concepts it likes to explain, but it does NOT provide you with an intuitive notion of what is going on. This is the most difficult part to learn. For example when studying group theory for physics (QM and field theory) you will need to have a notion of what this mathematical formalism is trying to achieve in "physical terms". I mean, for example it is very important to understand how group theory works in physics.

"Basically you want an equation to be invariant under some transformations. In order to achieve that, the elementary building blocks of this system need to transform according to the socalled irreducible representations of the symmetry group at hand. Quantumnumbers are used to denote these irreducible representations". "For example, if you want the probability of a wavefunction to be invariant under rotations, the wavefunction itself will have to transform as an irreducible representation of the rotation group"

If you are able to translate this in mathematical terms and apply this onto some field equation, you will very soon realize that the use of group theory in field theory is always analoguous. Then you will also be able to comprehend why a phonon has spin 0, why there are only 8 gluons and why a baryon exists out of 3 quarks and a meson out of 2 quarks. Or how quantumnumbers are "born" and why you have only that many values for the magnetic quantum number

I suppose, what i want to say here is : GO TO COLLEGE and BUY THOSE BOOKS, AND START STUDYING. You should not ask such questions like "what do i need to study for ..." here in a public forum. Go consult your student advisor at college.


marlon
 
Last edited:

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