Let L(T) be the closed-set latice of a tree T. The lower length l, (L(T)) of L (T) is defined as Call a set S of vertices in T a sparse set if d(x, y)/> 3 for any two distinct vertices x, y in S. The sparsity y(T) of T is defined as y(T) = max {Isl: s is a sparse set of T}. We prove that, for any
On the uniformity of the closed-set lattice of a tree
โ Scribed by K.M. Koh; K.S. Poh
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 578 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0012-365X
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โฆ Synopsis
Denote by e*(L) and ~,(L) respectively the upper length and lower length of a finite lattice L. The lattice L is said to be uniform if for each integer k with e,(L) < k < ยข*(L) there exists in L a maximal chain of length k. It is shown that the closed-set lattice of a finite graph G is uniform if G is a tree. The result is not necessarily true if G is not a tree.
๐ SIMILAR VOLUMES
Let \(X\) be a universal cover of a finite connected graph, and \(\Gamma\) a group acting discretely and cocompactly on \(X\), i.e., a uniform lattice on \(X\). We announce a proof of the conjecture of H. Bass and R. Kulkarni (J. Amer. Math. Soc. No. 4 (1990), 843-902) that the commensurability grou