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6-j symbol

Wigner's 6 − j symbols were introduced by Eugene Paul Wigner in 1940, and published in 1965. They are related to Racah's W-coefficients by

They have higher symmetry than Racah's W-coefficients.

Contents

Symmetry relations

The 6 − j symbol is invariant under the permutation of any two columns:

The 6 − j symbol is also invariant if upper and lower arguments are interchanged in any two columns:

The 6 − j symbol

is zero unless j1, j2, and j3 satisfy triangle conditions, i.e.,

In combination with the symmetry relation for interchanging upper and lower arguments this shows that triangle conditions must also be satisfied for (j1,j5,j6), (j4,j2,j6), and (j4,j5,j3).

Special case

When j6 = 0 the expression for the 6-j symbol is:

The function Δ(j1,j2,j3) is equal to 1 when (j1,j2,j3) satisfy the triangle conditions, and zero otherwise. The symmetry relations can be used to find the expression when another j is equal to zero.

Orthogonality relation

The 6-j symbols satisfy this orthogonality relation:

See also

External links

References

  • Biedenharn, L. C.; van Dam, H. (1965). Quantum Theory of Angular Momentum: A collection of Reprints and Original Papers. New York: Academic Press. ISBN 0120960567. 
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