Yang-Mills, QED, QCD and Yukawa theories

[Breo]

What is the difference between Yang-Mills and QED theories? Yukawa and QCD? specially in terms of the lagrangians.

I really want to get into this subject with a previously first sight.

 

[ofirg]

What is the difference between Yang-Mills and QED theories? Yukawa and QCD? specially in terms of the lagrangians.

I really want to get into this subject with a previously first sight.

Yang Mills and QCD ( which is just a particular Yang Mills theory) are based on non abelian gauge symmetries while QED is based on abelian gauge symmetry.

Yukawa theory doesn't have spin 1 particles, just fermions and scalars.

However, this is a very general question. I would recommend that you study the subject ( which would take some effort) and come back with more specific questions.

 

[Breo]

Why Yukawa focused on the search of the meson-neutron interaction?

 

[ofirg]

Why Yukawa focused on the search of the meson-neutron interaction?

In what context? do you mean focused on meson-neutron and not meson-proton interactions?

 

[Breo]

Nucleon* typo

 

[ofirg]

Nucleon* typo

In the Yukawa theory, the meson nucleon interaction is the pillar of theory. The nucleon-nucleon interaction is mediated by meson exchange, which is present due to the meson nucleon interaction.
The first and foremost prediction was that a meson with such properties exists, which was not known at the time the theory was published.

 

[ChrisVer]

Why did he focus on the pion-nucleons? Because nucleons are fermions spin 1/2 particles while pions are scalar spin 0 particles.
Of course the interaction Lagrangian would be an effective one, since it corresponds to energies lower than the QCD scale...