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In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)" , or the Eightfold Way , the successful classification scheme organizing the large number of lighter hadrons that ...
The standard model is a quantum field theory, meaning its fundamental objects are quantum fields, which are defined at all points in spacetime. QFT treats particles as excited states (also called quanta) of their underlying quantum fields, which are more fundamental than the particles. These fields are
A similar mysterious situation was with the Δ ++ baryon; in the quark model, it is composed of three up quarks with parallel spins. In 1964–65, Greenberg [ 19 ] and Han – Nambu [ 20 ] independently resolved the problem by proposing that quarks possess an additional SU(3) gauge degree of freedom , later called color charge.
A theory of quantum gravity is needed in order to reconcile these differences. [16] Whether this theory should be background-independent is an open question. The answer to this question will determine the understanding of what specific role gravitation plays in the fate of the universe.
The QCD vacuum is the quantum vacuum state of quantum chromodynamics (QCD). It is an example of a non-perturbative vacuum state, characterized by non-vanishing condensates such as the gluon condensate and the quark condensate in the complete theory which includes quarks.
In quantum field theory, scalar chromodynamics, also known as scalar quantum chromodynamics or scalar QCD, is a gauge theory consisting of a gauge field coupled to a scalar field. This theory is used experimentally to model the Higgs sector of the Standard Model. It arises from a coupling of a scalar field to gauge fields.
Despite being perhaps the most familiar fundamental interaction, gravity is not described by the Standard Model, due to contradictions that arise when combining general relativity, the modern theory of gravity, and quantum mechanics [54] [55]. However, gravity is so weak at microscopic scales, that it is essentially unmeasurable.
, whereas a down quark and an anti-up quark make up the π −, and these are the antiparticles of one another. The neutral pion π 0 is a combination of an up quark with an anti-up quark, or a down quark with an anti-down quark. The two combinations have identical quantum numbers, and hence they are only found in superpositions. The lowest ...