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Homomesy in products of three chains and multidimensional recombination. (English) Zbl 1427.05231
Summary: J. Propp and T. Roby [Electron. J. Comb. 22, No. 3, Research Paper P3.4, 29 p. (2015; Zbl 1319.05151)] isolated a phenomenon in which a statistic on a set has the same average value over any orbit as its global average, naming it homomesy. They proved that the cardinality statistic on order ideals of the product of two chains poset under rowmotion exhibits homomesy. In this paper, we prove an analogous result in the case of the product of three chains where one chain has two elements. In order to prove this result, we generalize from two to $$n$$ dimensions the recombination technique that D. Einstein and J. Propp [in: Proceedings of the 26th international conference on formal power series and algebraic combinatorics, FPSAC 2014, Chicago, IL, USA, June 29 – July 3, 2014. Nancy: The Association. Discrete Mathematics & Theoretical Computer Science (DMTCS). 513–524 (2014; Zbl 1394.06005)] developed to study homomesy. We see that our main homomesy result does not fully generalize to an arbitrary product of three chains, nor to larger products of chains; however, we have a partial generalization to an arbitrary product of three chains. Additional corollaries include refined homomesy results in the product of three chains and a new result on increasing tableaux. We conclude with a generalization of recombination to any ranked poset and a homomesy result for the Type B minuscule poset cross a two element chain.

##### MSC:
 05E18 Group actions on combinatorial structures 05E10 Combinatorial aspects of representation theory 06A11 Algebraic aspects of posets 06A07 Combinatorics of partially ordered sets
SageMath
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##### References:
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