Is QCD an extension of QED, or is QCD a “rival” of QED?
In: Physics
>Is QCD an extension of QED, or is QCD a “rival” of QED?
Neither, they explain different things. Quantum electrodynamics is the quantum field theory of electromagnetism, while quantum chromodynamics is the quantum field theory of the strong force. Electromagnetism is the force between charged particles mediated by photons (the same particles as the quantisation of light), and is responsible for electrons and nuclei being held together to form atoms, magnets, the repulsion between things when you touch something, etc. The strong force on the other hand is the force that holds together quarks (one of the fundamental particles) to make protons and neutrons, which are what then make up the nuclei of atoms.
The standard model of particle physics is built on both QCD and QED (along with another force, the weak force, but discussion of how that ties in can get complicated). As these forces are different, we need different field theories for them, so they are not extensions or competing theories.
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