Title
On orthogonal symmetric chain decompositions.
Abstract
The $n$-cube is the poset obtained by ordering all subsets of ${1,ldots,n}$ by inclusion. It is well-known that the $n$-cube can be partitioned into $binom{n}{lfloor n/2rfloor}$ chains, which is the minimum possible number. Two such decompositions of the $n$-cube are called orthogonal if any two chains of the decompositions share at most a single element. Shearer and Kleitman conjectured in 1979 that the $n$-cube has $lfloor n/2rfloor+1$ pairwise orthogonal decompositions into the minimum number of chains, and they constructed two such decompositions. Spink recently improved this by showing that the $n$-cube has three pairwise orthogonal chain decompositions for $ngeq 24$. In this paper, we construct four pairwise orthogonal chain decompositions of the $n$-cube for $ngeq 60$. We also construct five pairwise edge-disjoint chain decompositions of the $n$-cube for $ngeq 90$, where edge-disjointness is a slightly weaker notion than orthogonality.
Year
DOI
Venue
2018
10.37236/8531
arXiv: Combinatorics
Field
DocType
Volume
Discrete mathematics,Pairwise comparison,Combinatorics,Orthogonality,Mathematics,Partially ordered set
Journal
abs/1810.09847
Issue
Citations 
PageRank 
3
0
0.34
References 
Authors
0
4
Name
Order
Citations
PageRank
Karl Däubel100.34
Sven Jäger200.34
Torsten Mütze34312.88
Manfred Scheucher400.34