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Kronecker Coefficient


A Kronecker coefficient g(lambda,mu,nu) is the multiplicity of the complex Specht module S^nu in S^lambda tensor S^mu for the symmetric group S_n, where all three partitions have the same size n. Equivalently, writing chi^lambda for its group character,

 g(lambda,mu,nu)=1/(n!)sum_(sigma in S_n)chi^lambda(sigma)chi^mu(sigma)chi^nu(sigma)^_.
(1)

It is a nonnegative integer and is symmetric in the three partitions. For example, S^((2,1)) tensor S^((2,1)) for S_3 contains the trivial representation, the sign representation, and the two-dimensional irreducible representation, each once. Saxl's conjecture requires positivity of these coefficients when the first two partitions are the same staircase.

Let f^lambda denote the dimension of S^lambda. For every fixed A>0, Slonim (2026) reports the uniform asymptotic

 g(lambda,mu,nu)=(1+o(1))(f^lambdaf^muf^nu)/(n!)
(2)

as n->infty over all triples satisfying f^lambda,f^mu,f^nu>=sqrt(n!)exp(-Asqrt(n)). In particular, all these coefficients are eventually positive. The dimension condition describes deterministic sequences of partitions, not a probabilistic assertion about a random partition.

For the staircase rho_k=(k-1,k-2,...,1) of size n_rho=k(k-1)/2 and the square delta_k=(k^k) of size n_delta=k^2, Slonim (2026) reports

 g(rho_k,rho_k,rho_k)=(e^(-1/24)+o(1))((f^(rho_k))^3)/(n_rho!)
(3)

and

 g(delta_k,delta_k,delta_k)=(e^(-1/3)+o(1))((f^(delta_k))^3)/(n_delta!).
(4)

The dimension deficit of a partition lambda|-n means ln(sqrt(n!)/f^lambda). For these special shapes it is proportional to their sizes, so they are outside the preceding dimension range. Slonim attributes the mathematical statements and proofs to ChatGPT 6 Pro and states that the technical proofs have not been independently verified. The same work reports dimension-deficit and vanishing results for Littlewood-Richardson coefficients.


See also

Group Character, Littlewood-Richardson Coefficient, Saxl Conjecture, Specht Module, Tensor Square Conjecture, Vector Space Tensor Product

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References

Etingof, P.; Golberg, O.; Hensel, S.; Liu, T.; Schwendner, A.; Vaintrob, D.; and Yudovina, E. Introduction to Representation Theory. Providence, RI: Amer. Math. Soc., 2011. https://doi.org/10.1090/stml/059.Pak, I.; Panova, G.; and Vallejo, E. "Kronecker Products, Characters, Partitions, and the Tensor Square Conjectures." Adv. Math. 288, 702-731, 2016. https://doi.org/10.1016/j.aim.2015.11.002.Slonim, Z. "Kronecker Coefficients of Large Degree and Littlewood-Richardson Inequalities." 8 Nov 2026. https://arxiv.org/abs/2611.11593v1.

Cite this as:

Weisstein, Eric W. "Kronecker Coefficient." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/KroneckerCoefficient.html

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