Emmanuel Briand ; Rosa Orellana ; Mercedes Rosas
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Quasipolynomial formulas for the Kronecker coefficients indexed by two two―row shapes (extended abstract)
dmtcs:2735 -
Discrete Mathematics & Theoretical Computer Science,
January 1, 2009,
DMTCS Proceedings vol. AK, 21st International Conference on Formal Power Series and Algebraic Combinatorics (FPSAC 2009)
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https://doi.org/10.46298/dmtcs.2735
Quasipolynomial formulas for the Kronecker coefficients indexed by two two―row shapes (extended abstract)Article
Authors: Emmanuel Briand 1; Rosa Orellana 2; Mercedes Rosas 1
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Emmanuel Briand;Rosa Orellana;Mercedes Rosas
1 Departamento de Algebra [Sevilla]
2 Department of Mathematics [Dartmouth]
We show that the Kronecker coefficients indexed by two two―row shapes are given by quadratic quasipolynomial formulas whose domains are the maximal cells of a fan. Simple calculations provide explicitly the quasipolynomial formulas and a description of the associated fan. These new formulas are obtained from analogous formulas for the corresponding reduced Kronecker coefficients and a formula recovering the Kronecker coefficients from the reduced Kronecker coefficients. As an application, we characterize all the Kronecker coefficients indexed by two two-row shapes that are equal to zero. This allowed us to disprove a conjecture of Mulmuley about the behavior of the stretching functions attached to the Kronecker coefficients.