On Floors and Ceilings of the $k$-Catalan Arrangement
The set of dominant regions of the $k$-Catalan arrangement of a crystallographic root system $\Phi$ is a well-studied object enumerated by the Fuß-Catalan number $Cat^{(k)}(\Phi)$. It is natural to refine this enumeration by considering floors and ceilings of dominant regions. A conjecture of Armstrong states that counting dominant regions by their number of floors of a certain height gives the same distribution as counting dominant regions by their number of ceilings of the same height. We prove this conjecture using a bijection that provides even more refined enumerative information.
2009 ◽
Vol DMTCS Proceedings vol. AK,...
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2009 ◽
Vol 35
(6)
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pp. 1030-1037
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1964 ◽
Vol 56
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pp. 359-361
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1980 ◽
Vol 20
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pp. 384-386
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