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3-j symbol

(Redirected fromWigner 3-j symbols)

Inquantum mechanics, theWigner's 3-j symbols, also called 3-jm symbols, are an alternative toClebsch–Gordan coefficients for the purpose of adding angular momenta.[1] While the two approaches address exactly the same physical problem, the 3-j symbols do so more symmetrically.

Mathematical relation to Clebsch–Gordan coefficients

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The 3-j symbols are given in terms of the Clebsch–Gordan coefficients by

(j1j2j3m1m2m3)(1)j1j2m32j3+1j1m1j2m2|j3(m3).{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}\equiv {\frac {(-1)^{j_{1}-j_{2}-m_{3}}}{\sqrt {2j_{3}+1}}}\langle j_{1}\,m_{1}\,j_{2}\,m_{2}|j_{3}\,(-m_{3})\rangle .} 

Thej andm components are angular-momentum quantum numbers, i.e., everyj (and every correspondingm) is either a nonnegative integer orhalf-odd-integer. The exponent of the sign factor is always an integer, so it remains the same when transposed to the left, and the inverse relation follows upon making the substitutionm3 → −m3:

j1m1j2m2|j3m3=(1)j1+j2m32j3+1(j1j2j3m1m2m3).{\displaystyle \langle j_{1}\,m_{1}\,j_{2}\,m_{2}|j_{3}\,m_{3}\rangle =(-1)^{-j_{1}+j_{2}-m_{3}}{\sqrt {2j_{3}+1}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&-m_{3}\end{pmatrix}}.} 

Explicit expression

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(j1j2j3m1m2m3)δ(m1+m2+m3,0)(1)j1j2m3(j1+j2j3)!(j1j2+j3)!(j1+j2+j3)!(j1+j2+j3+1)! ××(j1m1)!(j1+m1)!(j2m2)!(j2+m2)!(j3m3)!(j3+m3)! ××k=KN(1)kk!(j1+j2j3k)!(j1m1k)!(j2+m2k)!(j3j2+m1+k)!(j3j1m2+k)!,{\displaystyle {\begin{aligned}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}&\equiv \delta (m_{1}+m_{2}+m_{3},0)(-1)^{j_{1}-j_{2}-m_{3}}{}{\sqrt {\frac {(j_{1}+j_{2}-j_{3})!(j_{1}-j_{2}+j_{3})!(-j_{1}+j_{2}+j_{3})!}{(j_{1}+j_{2}+j_{3}+1)!}}}\ \times {}\\[6pt]&\times {\sqrt {(j_{1}-m_{1})!(j_{1}+m_{1})!(j_{2}-m_{2})!(j_{2}+m_{2})!(j_{3}-m_{3})!(j_{3}+m_{3})!}}\ \times {}\\[6pt]&\times \sum _{k=K}^{N}{\frac {(-1)^{k}}{k!(j_{1}+j_{2}-j_{3}-k)!(j_{1}-m_{1}-k)!(j_{2}+m_{2}-k)!(j_{3}-j_{2}+m_{1}+k)!(j_{3}-j_{1}-m_{2}+k)!}},\end{aligned}}} 

whereδ(i,j){\displaystyle \delta (i,j)}  is theKronecker delta.

The summation is performed over those integer valuesk for which the argument of eachfactorial in the denominator is non-negative, i.e. summation limitsK andN are taken equal: the lower oneK=max(0,j2j3m1,j1j3+m2),{\displaystyle K=\max(0,j_{2}-j_{3}-m_{1},j_{1}-j_{3}+m_{2}),}  the upper oneN=min(j1+j2j3,j1m1,j2+m2).{\displaystyle N=\min(j_{1}+j_{2}-j_{3},j_{1}-m_{1},j_{2}+m_{2}).}  Factorials of negative numbers are conventionally taken equal to zero, so that the values of the 3j symbol at, for example,j3>j1+j2{\displaystyle j_{3}>j_{1}+j_{2}}  orj1<m1{\displaystyle j_{1}<m_{1}}  are automatically set to zero.

Definitional relation to Clebsch–Gordan coefficients

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The CG coefficients are defined so as to express the addition of two angular momenta in terms of a third:

|j3m3=m1=j1j1m2=j2j2j1m1j2m2|j3m3|j1m1j2m2.{\displaystyle |j_{3}\,m_{3}\rangle =\sum _{m_{1}=-j_{1}}^{j_{1}}\sum _{m_{2}=-j_{2}}^{j_{2}}\langle j_{1}\,m_{1}\,j_{2}\,m_{2}|j_{3}\,m_{3}\rangle |j_{1}\,m_{1}\,j_{2}\,m_{2}\rangle .} 

The 3-j symbols, on the other hand, are the coefficients with which three angular momenta must be added so that the resultant is zero:

m1=j1j1m2=j2j2m3=j3j3|j1m1|j2m2|j3m3(j1j2j3m1m2m3)=|00.{\displaystyle \sum _{m_{1}=-j_{1}}^{j_{1}}\sum _{m_{2}=-j_{2}}^{j_{2}}\sum _{m_{3}=-j_{3}}^{j_{3}}|j_{1}m_{1}\rangle |j_{2}m_{2}\rangle |j_{3}m_{3}\rangle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}=|0\,0\rangle .} 

Here|00{\displaystyle |0\,0\rangle }  is the zero-angular-momentum state (j=m=0{\displaystyle j=m=0} ). It is apparent that the 3-j symbol treats all three angular momenta involved in the addition problem on an equal footing and is therefore more symmetrical than the CG coefficient.

Since the state|00{\displaystyle |0\,0\rangle }  is unchanged by rotation, one also says that the contraction of the product of three rotational states with a 3-j symbol is invariant under rotations.

Selection rules

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The Wigner 3-j symbol is zero unless all these conditions are satisfied:

mi{ji,ji+1,ji+2,,ji}(i=1,2,3),m1+m2+m3=0,|j1j2|j3j1+j2,(j1+j2+j3) is an integer (and, moreover, an even integer if m1=m2=m3=0).{\displaystyle {\begin{aligned}&m_{i}\in \{-j_{i},-j_{i}+1,-j_{i}+2,\ldots ,j_{i}\}\quad (i=1,2,3),\\&m_{1}+m_{2}+m_{3}=0,\\&|j_{1}-j_{2}|\leq j_{3}\leq j_{1}+j_{2},\\&(j_{1}+j_{2}+j_{3}){\text{ is an integer (and, moreover, an even integer if }}m_{1}=m_{2}=m_{3}=0{\text{)}}.\\\end{aligned}}} 

Symmetry properties

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A 3-j symbol is invariant under an even permutation of its columns:

(j1j2j3m1m2m3)=(j2j3j1m2m3m1)=(j3j1j2m3m1m2).{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}={\begin{pmatrix}j_{2}&j_{3}&j_{1}\\m_{2}&m_{3}&m_{1}\end{pmatrix}}={\begin{pmatrix}j_{3}&j_{1}&j_{2}\\m_{3}&m_{1}&m_{2}\end{pmatrix}}.} 

An odd permutation of the columns gives a phase factor:

(j1j2j3m1m2m3)=(1)j1+j2+j3(j2j1j3m2m1m3){\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}=(-1)^{j_{1}+j_{2}+j_{3}}{\begin{pmatrix}j_{2}&j_{1}&j_{3}\\m_{2}&m_{1}&m_{3}\end{pmatrix}}} 
=(1)j1+j2+j3(j1j3j2m1m3m2)=(1)j1+j2+j3(j3j2j1m3m2m1).{\displaystyle =(-1)^{j_{1}+j_{2}+j_{3}}{\begin{pmatrix}j_{1}&j_{3}&j_{2}\\m_{1}&m_{3}&m_{2}\end{pmatrix}}=(-1)^{j_{1}+j_{2}+j_{3}}{\begin{pmatrix}j_{3}&j_{2}&j_{1}\\m_{3}&m_{2}&m_{1}\end{pmatrix}}.} 

Changing the sign of them{\displaystyle m}  quantum numbers (time reversal) also gives a phase:

(j1j2j3m1m2m3)=(1)j1+j2+j3(j1j2j3m1m2m3).{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\-m_{1}&-m_{2}&-m_{3}\end{pmatrix}}=(-1)^{j_{1}+j_{2}+j_{3}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}.} 

The 3-j symbols also have so-called Regge symmetries, which are not due to permutations or time reversal.[2] These symmetries are:

(j1j2j3m1m2m3)=(j1j2+j3m12j2+j3+m12j3j2j2j3m12m3j2j3+m12+m3),{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}={\begin{pmatrix}j_{1}&{\frac {j_{2}+j_{3}-m_{1}}{2}}&{\frac {j_{2}+j_{3}+m_{1}}{2}}\\j_{3}-j_{2}&{\frac {j_{2}-j_{3}-m_{1}}{2}}-m_{3}&{\frac {j_{2}-j_{3}+m_{1}}{2}}+m_{3}\end{pmatrix}},} 
(j1j2j3m1m2m3)=(1)j1+j2+j3(j2+j3+m12j1+j3+m22j1+j2+m32j1j2+j3m12j2j1+j3m22j3j1+j2m32).{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}=(-1)^{j_{1}+j_{2}+j_{3}}{\begin{pmatrix}{\frac {j_{2}+j_{3}+m_{1}}{2}}&{\frac {j_{1}+j_{3}+m_{2}}{2}}&{\frac {j_{1}+j_{2}+m_{3}}{2}}\\j_{1}-{\frac {j_{2}+j_{3}-m_{1}}{2}}&j_{2}-{\frac {j_{1}+j_{3}-m_{2}}{2}}&j_{3}-{\frac {j_{1}+j_{2}-m_{3}}{2}}\end{pmatrix}}.} 

With the Regge symmetries, the 3-j symbol has a total of 72 symmetries. These are best displayed by the definition of a Regge symbol, which is a one-to-one correspondence between it and a 3-j symbol and assumes the properties of a semi-magic square:[3]

R=j1+j2+j3j1j2+j3j1+j2j3j1m1j2m2j3m3j1+m1j2+m2j3+m3,{\displaystyle R={\begin{array}{|ccc|}\hline -j_{1}+j_{2}+j_{3}&j_{1}-j_{2}+j_{3}&j_{1}+j_{2}-j_{3}\\j_{1}-m_{1}&j_{2}-m_{2}&j_{3}-m_{3}\\j_{1}+m_{1}&j_{2}+m_{2}&j_{3}+m_{3}\\\hline \end{array}},} 

whereby the 72 symmetries now correspond to 3! row and 3! column interchanges plus a transposition of the matrix. These facts can be used to devise an effective storage scheme.[3]

Orthogonality relations

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A system of two angular momenta with magnitudesj1 andj2 can be described either in terms of the uncoupled basis states (labeled by the quantum numbersm1 andm2), or the coupled basis states (labeled byj3 andm3). The 3-j symbols constitute a unitary transformation between these two bases, and this unitarity implies the orthogonality relations

(2j3+1)m1m2(j1j2j3m1m2m3)(j1j2j3m1m2m3)=δj3,j3δm3,m3{j1j2j3},{\displaystyle (2j_{3}+1)\sum _{m_{1}m_{2}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}{\begin{pmatrix}j_{1}&j_{2}&j'_{3}\\m_{1}&m_{2}&m'_{3}\end{pmatrix}}=\delta _{j_{3},j'_{3}}\delta _{m_{3},m'_{3}}{\begin{Bmatrix}j_{1}&j_{2}&j_{3}\end{Bmatrix}},} 
j3m3(2j3+1)(j1j2j3m1m2m3)(j1j2j3m1m2m3)=δm1,m1δm2,m2.{\displaystyle \sum _{j_{3}m_{3}}(2j_{3}+1){\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}'&m_{2}'&m_{3}\end{pmatrix}}=\delta _{m_{1},m_{1}'}\delta _{m_{2},m_{2}'}.} 

Thetriangular delta{j1 j2 j3} is equal to 1 when the triad (j1,j2,j3) satisfies the triangle conditions, and is zero otherwise. The triangular delta itself is sometimes confusingly called[4] a "3-j symbol" (without them) in analogy to6-j and9-j symbols, all of which are irreducible summations of 3-jm symbols where nom variables remain.

Relation to spherical harmonics; Gaunt coefficients

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The 3-jm symbols give the integral of the products of threespherical harmonics[5]

Yl1m1(θ,φ)Yl2m2(θ,φ)Yl3m3(θ,φ)sinθdθdφ=(2l1+1)(2l2+1)(2l3+1)4π(l1l2l3000)(l1l2l3m1m2m3){\displaystyle {\begin{aligned}&\int Y_{l_{1}m_{1}}(\theta ,\varphi )Y_{l_{2}m_{2}}(\theta ,\varphi )Y_{l_{3}m_{3}}(\theta ,\varphi )\,\sin \theta \,\mathrm {d} \theta \,\mathrm {d} \varphi \\&\quad ={\sqrt {\frac {(2l_{1}+1)(2l_{2}+1)(2l_{3}+1)}{4\pi }}}{\begin{pmatrix}l_{1}&l_{2}&l_{3}\\0&0&0\end{pmatrix}}{\begin{pmatrix}l_{1}&l_{2}&l_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}\end{aligned}}} 

withl1{\displaystyle l_{1}} ,l2{\displaystyle l_{2}}  andl3{\displaystyle l_{3}}  integers. These integrals are called Gaunt coefficients.

Relation to integrals of spin-weighted spherical harmonics

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Similar relations exist for thespin-weighted spherical harmonics ifs1+s2+s3=0{\displaystyle s_{1}+s_{2}+s_{3}=0} :

dn^s1Yj1m1(n^)s2Yj2m2(n^)s3Yj3m3(n^)=(2j1+1)(2j2+1)(2j3+1)4π(j1j2j3m1m2m3)(j1j2j3s1s2s3).{\displaystyle {\begin{aligned}&\int d\mathbf {\hat {n}} \,_{s_{1}}\!Y_{j_{1}m_{1}}(\mathbf {\hat {n}} )\,_{s_{2}}\!Y_{j_{2}m_{2}}(\mathbf {\hat {n}} )\,_{s_{3}}\!Y_{j_{3}m_{3}}(\mathbf {\hat {n}} )\\&\quad ={\sqrt {\frac {(2j_{1}+1)(2j_{2}+1)(2j_{3}+1)}{4\pi }}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\-s_{1}&-s_{2}&-s_{3}\end{pmatrix}}.\end{aligned}}} 

Recursion relations

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(l3s3)(l3±s3+1)(l1l2l3s1s2s3±1)==(l1s1)(l1±s1+1)(l1l2l3s1±1s2s3)+(l2s2)(l2±s2+1)(l1l2l3s1s2±1s3).{\displaystyle {\begin{aligned}&{-}{\sqrt {(l_{3}\mp s_{3})(l_{3}\pm s_{3}+1)}}{\begin{pmatrix}l_{1}&l_{2}&l_{3}\\s_{1}&s_{2}&s_{3}\pm 1\end{pmatrix}}=\\&\quad ={\sqrt {(l_{1}\mp s_{1})(l_{1}\pm s_{1}+1)}}{\begin{pmatrix}l_{1}&l_{2}&l_{3}\\s_{1}\pm 1&s_{2}&s_{3}\end{pmatrix}}+{\sqrt {(l_{2}\mp s_{2})(l_{2}\pm s_{2}+1)}}{\begin{pmatrix}l_{1}&l_{2}&l_{3}\\s_{1}&s_{2}\pm 1&s_{3}\end{pmatrix}}.\end{aligned}}} 

Asymptotic expressions

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Forl1l2,l3{\displaystyle l_{1}\ll l_{2},l_{3}}  a non-zero 3-j symbol is

(l1l2l3m1m2m3)(1)l3+m3dm1,l3l2l1(θ)2l3+1,{\displaystyle {\begin{pmatrix}l_{1}&l_{2}&l_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}\approx (-1)^{l_{3}+m_{3}}{\frac {d_{m_{1},l_{3}-l_{2}}^{l_{1}}(\theta )}{\sqrt {2l_{3}+1}}},} 

wherecos(θ)=2m3/(2l3+1){\displaystyle \cos(\theta )=-2m_{3}/(2l_{3}+1)} , anddmnl{\displaystyle d_{mn}^{l}}  is aWigner function. Generally a better approximation obeying the Regge symmetry is given by

(l1l2l3m1m2m3)(1)l3+m3dm1,l3l2l1(θ)l2+l3+1,{\displaystyle {\begin{pmatrix}l_{1}&l_{2}&l_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}\approx (-1)^{l_{3}+m_{3}}{\frac {d_{m_{1},l_{3}-l_{2}}^{l_{1}}(\theta )}{\sqrt {l_{2}+l_{3}+1}}},} 

wherecos(θ)=(m2m3)/(l2+l3+1){\displaystyle \cos(\theta )=(m_{2}-m_{3})/(l_{2}+l_{3}+1)} .

Metric tensor

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The following quantity acts as ametric tensor in angular-momentum theory and is also known as aWigner 1-jm symbol:[1]

(jmm):=2j+1(j0jm0m)=(1)jmδm,m.{\displaystyle {\begin{pmatrix}j\\m\quad m'\end{pmatrix}}:={\sqrt {2j+1}}{\begin{pmatrix}j&0&j\\m&0&m'\end{pmatrix}}=(-1)^{j-m'}\delta _{m,-m'}.} 

It can be used to perform time reversal on angular momenta.

Special cases and other properties

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m(1)jm(jjJmm0)=2j+1δJ,0.{\displaystyle \sum _{m}(-1)^{j-m}{\begin{pmatrix}j&j&J\\m&-m&0\end{pmatrix}}={\sqrt {2j+1}}\,\delta _{J,0}.} 

From equation (3.7.9) in[6]

(jj0mm0)=12j+1(1)jm.{\displaystyle {\begin{pmatrix}j&j&0\\m&-m&0\end{pmatrix}}={\frac {1}{\sqrt {2j+1}}}(-1)^{j-m}.} 
1211Pl1(x)Pl2(x)Pl(x)dx=(ll1l2000)2,{\displaystyle {\frac {1}{2}}\int _{-1}^{1}P_{l_{1}}(x)P_{l_{2}}(x)P_{l}(x)\,dx={\begin{pmatrix}l&l_{1}&l_{2}\\0&0&0\end{pmatrix}}^{2},} 

whereP areLegendre polynomials.

Relation to RacahV-coefficients

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Wigner 3-j symbols are related toRacahV-coefficients[7] by a simple phase:

V(j1j2j3;m1m2m3)=(1)j1j2j3(j1j2j3m1m2m3).{\displaystyle V(j_{1}\,j_{2}\,j_{3};m_{1}\,m_{2}\,m_{3})=(-1)^{j_{1}-j_{2}-j_{3}}{\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}.} 

Relation to group theory

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This section essentially recasts thedefinitional relationin the language of group theory.

Agroup representation of agroup is ahomomorphism of the group intoa group oflinear transformations over some vector space. The lineartransformations can be given by a group of matrices with respect to some basis of the vector space.

The group of transformations leaving angular momenta invariant is the three dimensional rotation groupSO(3). When "spin" angular momenta are included, the group is itsdouble covering group,SU(2).

A reducible representation is one where a change of basis can be applied to bring all the matrices into block diagonal form. A representationisirreducible (irrep) if no such transformation exists.

For each value ofj, the 2j+1 kets form a basis for an irreducible representation (irrep) ofSO(3)/SU(2) over the complex numbers. Given twoirreps, thetensor direct product can be reduced to asum of irreps, giving rise to the Clebcsh-Gordon coefficients, or by reduction of the triple product of three irreps to thetrivial irrep1 giving rise to the 3j symbols.

3j symbols for other groups

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The3j{\displaystyle 3j}  symbol has been most intensely studied in the context of the coupling of angular momentum. For this, it is strongly related to thegroup representation theory of the groups SU(2) and SO(3)as discussed above. However, manyother groups are of importance inphysics andchemistry,and there has been much work on the3j{\displaystyle 3j}  symbol for these other groups.In this section, some of that work is considered.

Simply reducible groups

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The original paper by Wigner[1]was not restricted to SO(3)/SU(2)but instead focussed on simply reducible (SR) groups.These are groups in which

  • all classes are ambivalent i.e. ifX{\displaystyle X}  is a member of a class then so isX1{\displaystyle X^{-1}} 
  • the Kronecker product of two irreps is multiplicity free i.e. does not contain any irrep more than once.

For SR groups, every irrep is equivalent to its complex conjugate,and under permutations of the columns the absolute value of thesymbol is invariant and the phase of each can be chosen so thatthey at most change sign under odd permutations and remainunchanged under even permutations.

General compact groups

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Compact groups form a wide class of groups withtopological structure.They include the finite groups with addeddiscrete topologyand many of theLie groups.

General compact groups will neither be ambivalent nor multiplicity free.Derome and Sharp[8]and Derome[9] examined the3j{\displaystyle 3j}  symbolfor the general case using the relation to the Clebsch-Gordon coefficients of

(j1j2j3m1m2m3)1[j3]j1m1j2m2|j3m3.{\displaystyle {\begin{pmatrix}j_{1}&j_{2}&j_{3}\\m_{1}&m_{2}&m_{3}\end{pmatrix}}\equiv {\frac {1}{[j_{3}]}}\langle j_{1}\,m_{1}\,j_{2}\,m_{2}|j_{3}^{*}\,m_{3}\rangle .} 

where[j]{\displaystyle [j]}  is the dimension of the representation space ofj{\displaystyle j}  andj3{\displaystyle j_{3}^{*}}  is the complex conjugaterepresentation toj3{\displaystyle j_{3}} .

By examining permutations of columns of the3j{\displaystyle 3j}  symbol, they showed three cases:

Further research into3j{\displaystyle 3j}  symbols for compact groups has been performed based on these principles.[11]

SU(n)

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TheSpecial unitary group SU(n) is theLie group of n × n unitary matrices with determinant 1.

The groupSU(3) is important inparticle theory.There are many papers dealing with the3j{\displaystyle 3j}  orequivalent symbol[12][13][14][15][16][17][18][19]

The3j{\displaystyle 3j}  symbol for the group SU(4) has been studied[20][21]while there is also work on the general SU(n) groups[22][23]

Crystallographic point groups

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There are many papers dealing with the3j{\displaystyle 3j}  symbols or Clebsch-Gordon coefficients for the finitecrystallographic point groupsand thedouble point groupsThe book by Butler[24]references these and details the theory along with tables.

Magnetic groups

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Magnetic groups include antilinear operators as well as linear operators. They need to be dealt with usingWigner's theory ofcorepresentations of unitary and antiunitary groups.A significant departure from standard representation theory is that the multiplicity of the irreducible corepresentationj3{\displaystyle j_{3}^{*}} in the direct product of the irreducible corepresentationsj1j2{\displaystyle j_{1}\otimes j_{2}} is generally smaller than the multiplicity of the trivial corepresentation in the tripleproductj1j2j3{\displaystyle j_{1}\otimes j_{2}\otimes j_{3}} , leading to significant differences between the Clebsch-Gordoncoefficients and the3j{\displaystyle 3j}  symbol.

The3j{\displaystyle 3j}  symbols have been examined for the grey groups[25][26]and for the magnetic point groups[27]

See also

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References

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  1. ^abcWigner, E. P. (1993). "On the Matrices Which Reduce the Kronecker Products of Representations of S. R. Groups". In Wightman, Arthur S. (ed.).The Collected Works of Eugene Paul Wigner. Vol. A/1. pp. 608–654.doi:10.1007/978-3-662-02781-3_42.ISBN 978-3-642-08154-5.
  2. ^Regge, T. (1958). "Symmetry Properties of Clebsch-Gordan Coefficients".Nuovo Cimento.10 (3): 544.Bibcode:1958NCim...10..544R.doi:10.1007/BF02859841.S2CID 122299161.
  3. ^abRasch, J.; Yu, A. C. H. (2003). "Efficient Storage Scheme for Pre-calculated Wigner 3j, 6j and Gaunt Coefficients".SIAM J. Sci. Comput.25 (4):1416–1428.doi:10.1137/s1064827503422932.
  4. ^P. E. S. Wormer; J. Paldus (2006). "Angular Momentum Diagrams".Advances in Quantum Chemistry.51. Elsevier:59–124.Bibcode:2006AdQC...51...59W.doi:10.1016/S0065-3276(06)51002-0.ISBN 9780120348510.ISSN 0065-3276.
  5. ^Cruzan, Orval R. (1962)."Translational addition theorems for spherical vector wave functions".Quarterly of Applied Mathematics.20 (1):33–40.doi:10.1090/qam/132851.ISSN 0033-569X.
  6. ^Edmonds, Alan (1957).Angular Momentum in Quantum Mechanics. Princeton University Press.
  7. ^Racah, G. (1942). "Theory of Complex Spectra II".Physical Review.62 (9–10):438–462.Bibcode:1942PhRv...62..438R.doi:10.1103/PhysRev.62.438.
  8. ^Derome, J-R; Sharp, W. T. (1965). "Racah Algebra for an Arbitrary Group".J. Math. Phys.6 (10):1584–1590.Bibcode:1965JMP.....6.1584D.doi:10.1063/1.1704698.
  9. ^Derome, J-R (1966). "Symmetry Properties of the 3j Symbols for an Arbitrary Group".J. Math. Phys.7 (4):612–615.Bibcode:1966JMP.....7..612D.doi:10.1063/1.1704973.
  10. ^Newmarch, J. D. (1983). "On the 3j symmetries".J. Math. Phys.24 (4):757–764.Bibcode:1983JMP....24..757N.doi:10.1063/1.525771.
  11. ^Butler, P. H.; Wybourne, B. G. (1976). "Calculation ofj andjm Symbols forArbitrary Compact Groups. I. Methodology".Int. J. Quantum Chem.X (4):581–598.doi:10.1002/qua.560100404.
  12. ^Moshinsky, Marcos (1962). "Wigner coefficients for the SU3 group and some applications".Rev. Mod. Phys.34 (4): 813.Bibcode:1962RvMP...34..813M.doi:10.1103/RevModPhys.34.813.
  13. ^P. McNamee, S. J.; Chilton, Frank (1964). "Tables of Clebsch-Gordan coefficients of SU3".Rev. Mod. Phys.36 (4): 1005.Bibcode:1964RvMP...36.1005M.doi:10.1103/RevModPhys.36.1005.
  14. ^Draayer, J. P.; Akiyama, Yoshimi (1973)."Wigner and Racah coefficients for SU3"(PDF).J. Math. Phys.14 (12): 1904.Bibcode:1973JMP....14.1904D.doi:10.1063/1.1666267.hdl:2027.42/70151.
  15. ^Akiyama, Yoshimi; Draayer, J. P. (1973). "A users' guide to fortran programs for Wigner and Racah coefficients of SU3".Comput. Phys. Commun.5 (6): 405.Bibcode:1973CoPhC...5..405A.doi:10.1016/0010-4655(73)90077-5.hdl:2027.42/24983.
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