Quantum Mechanics/Quantum Chromodynamics

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The QCD (Quantum ChromoDynamics) is the current theoretical framework used to describe the strong interaction ("force") which is responsible for existence of numerous barion and meson nuclear particles. Mathematically it is the specific QFT (Quantum Field Theoretic) model from the class of Yang-Mills (YM) "gauge" theories, this one based on the gauge (i.e. localized) symmetry group SU(3).

Yang-Mills models of fundamental interactions

The Yang-Mills theories of gauge interactions describe the matter as one of two types of the substance:

The concept of gauge (i.e. localized) symmetries plays the fundamental role in YM theories. The idea is to start with a physical model that has certain global symmetry (here "global" meaning using the same transformation parameters at every point if space-time), and try to see if that physical model can be generalized to support the same symmetry applied with different values at different points in the space-time. Such procedure (called "gauging the symmetry", i.e. making it local) brings into the model the additional fields (the "gauge" fields) which look as the generalization of the Maxwell's electromagnetic fields. One nontrivial element of this generalization is that if the gauge symmetry is non-Abelian (e.g. the SO(N), SU(N), etc.), the gauge field acquire the self-interaction terms, i.e. the corresponding gauge bosons can generate more of the similar bosons (which does not happen for photons corresponding to the Abelian group U(1)).

The other modern uses of the Yang-Mills models are

Interaction Model/Theory Symmetry Source matter Source charge Mediating bosons
Electromagnetic interaction Maxwell's theoryU(1)Charged particlesElectric charge Photon
Electro-weak interactionStandard ModelU(1)xSU(2)Leptons and quarkselectromagnetic and weak chargesPhoton, Wikons (Z0, W+, W-)
Strong interactionQuantum ChromoDynamicsSU(3)Quarks"Color" chargeGluons (8 types)
GravityEinstein's General RelativityR4xSO(1,3)All matter with energyenergy, momentum, stress, pressuregravitons

Back to Quantum ChromoDynamics

TO BE CONTINUED.

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