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A sigma with a subscript x, y or z, three two-by-two matrices.
Also known as: Pauli spin matrices, Sigma matrices, Spin matrices
The three Pauli matrices describe the spin of an electron, and they anticommute with each other — swapping any two flips a sign. They are also the generators of rotations in the two-component spinor space, which is why a spin-half particle needs a full 720-degree turn to return to itself.
Denotes the three 2×2 Hermitian matrices representing the components of spin-half angular momentum.
Contexts: Laboratory
Anticommute pairwise and square to the identity, which is the algebra that defines spin-half behaviour.
Contexts: Laboratory
Generate rotations in spinor space, which is why a spin-half state returns to itself only after a rotation of 720 degrees.
Contexts: Laboratory
A Greek lowercase sigma with a small letter x, y or z set below and to the right.