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The twofold multiplicity problem associated with the Wigner supermultiplet reduction SU(4) ⊃ SU(2) ⊗ SU(2) is resolved by spin-isospin projection techniques analogous to the angular momentum projection technique introduced by Elliott to resolve the SU(3) ⊃ R(3) multiplicity problem. The projection quantum numbers, which furnish either an integer or half-integer characterization of the multiplicity, are assigned according to an (sT)-multiplicity formula derived from a consideration of the symmetry properties of spin-isospin degeneracy diagrams. An expression is obtained for the coefficients which relate the SU(4) ⊃ SU(2) ⊗ SU(2) projected basis states to states labeled according to the natural U(4) ⊃ U(3) ⊃ U(2) ⊃ U(1) chain. General expressions for SU(4) ⊃ SU(2) ⊗ SU(2) coupling coefficients and tensorial matrix elements are given in terms of the corresponding U(4) ⊃ U(3) ⊃ U(2) ⊃ U(1) quantities.

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Journal of Mathematical Physics

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