Decomposable compositions, symmetric quasisymmetric functions and equality of ribbon Schur functions |
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Authors: | Louis J Billera Hugh Thomas Stephanie van Willigenburg |
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Affiliation: | a Department of Mathematics, Cornell University, Ithaca, NY 14853-4201, USA b Fields Institute, 222 College St., Toronto, Ont. Canada M5T 3J1 c Department of Mathematics, University of British Columbia, Vancouver, BC Canada V6T 1Z2 |
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Abstract: | We define an equivalence relation on integer compositions and show that two ribbon Schur functions are identical if and only if their defining compositions are equivalent in this sense. This equivalence is completely determined by means of a factorization for compositions: equivalent compositions have factorizations that differ only by reversing some of the terms. As an application, we can derive identities on certain Littlewood-Richardson coefficients.Finally, we consider the cone of symmetric functions having a nonnnegative representation in terms of the fundamental quasisymmetric basis. We show the Schur functions are among the extremes of this cone and conjecture its facets are in bijection with the equivalence classes of compositions. |
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Keywords: | primary 05E05 05A17 secondary 05A19 05E10 |
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