David Einstein ; Miriam Farber ; Emily Gunawan ; Michael Joseph ; Matthew Macauley et al.
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Noncrossing partitions, toggles, and homomesy
dmtcs:6378 -
Discrete Mathematics & Theoretical Computer Science,
April 22, 2020,
DMTCS Proceedings, 28th International Conference on Formal Power Series and Algebraic Combinatorics (FPSAC 2016)
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https://doi.org/10.46298/dmtcs.6378
Noncrossing partitions, toggles, and homomesyArticle
Authors: David Einstein 1; Miriam Farber 2; Emily Gunawan 3; Michael Joseph 4; Matthew Macauley 5; James Propp 1; Simon Rubinstein-Salzedo
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David Einstein;Miriam Farber;Emily Gunawan;Michael Joseph;Matthew Macauley;James Propp;Simon Rubinstein-Salzedo
1 Department of Mathematics [Lowell]
2 Department of Mathematics [MIT]
3 Department of Mathematics [Minneapolis]
4 Department of Mathematics [Storrs]
5 Department of Mathematical Sciences [Clemson]
We introduce n(n − 1)/2 natural involutions (“toggles”) on the set S of noncrossing partitions π of size n, along with certain composite operations obtained by composing these involutions. We show that for many operations T of this kind, a surprisingly large family of functions f on S (including the function that sends π to the number of blocks of π) exhibits the homomesy phenomenon: the average of f over the elements of a T -orbit is the same for all T -orbits. Our methods apply more broadly to toggle operations on independent sets of certain graphs.