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Spin is an intrinsic form of angular momentum carried by elementary particles, and thus by composite particles such as hadrons, atomic nuclei, and atoms. [1] [2]: 183–184 Spin is quantized, and accurate models for the interaction with spin require relativistic quantum mechanics or quantum field theory.
A spin model is a mathematical model used in physics primarily to explain magnetism. Spin models may either be classical or quantum mechanical in nature. Spin models have been studied in quantum field theory as examples of integrable models. Spin models are also used in quantum information theory and computability theory in theoretical computer ...
The spin magnetic moment of the electron is =, where is the spin (or intrinsic angular-momentum) vector, is the Bohr magneton, and = is the electron-spin g-factor. Here μ {\displaystyle {\boldsymbol {\mu }}} is a negative constant multiplied by the spin , so the spin magnetic moment is antiparallel to the spin.
The phenomenon can be explained with the spatial quantization of the spin moment of momentum. In atoms the electrons are paired such that one spins upward and one downward, neutralizing the effect of their spin on the action of the atom as a whole. But in the valence shell of silver atoms, there is a single electron whose spin remains unbalanced.
The hypothetical graviton has spin = 2; it is unknown whether it is a gauge boson as well. In the Standard Model, elementary particles are represented for predictive utility as point particles. Though extremely successful, the Standard Model is limited by its omission of gravitation and has some parameters arbitrarily added but unexplained. [10]
When two spin-polarized atoms in their ground state experience a spin-exchange collision, the total spin of the atoms is preserved yet the orientation of the individual spins may change. For example, if atoms A {\displaystyle A} and B {\displaystyle B} are oppositely polarized , a spin-exchange collision reverses the spins: [ 2 ]
The graviton must be a spin-2 boson because the source of gravitation is the stress–energy tensor, a second-order tensor (compared with electromagnetism's spin-1 photon, the source of which is the four-current, a first-order tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from ...
By contrast, an isolated Ni atom (electron configuration = 3d 8 4s 2) in a cubic crystal field will have two unpaired electrons of the same spin (hence, =) and would thus be expected to have in the localized electron model a total spin magnetic moment of = (but the measured spin-only magnetic moment along one axis, the physical observable, will ...