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The 2-intersection number of paths and bounded-degree trees

✍ Scribed by Michael S. Jacobson; André E. Kézdy; Douglas B. West


Publisher
John Wiley and Sons
Year
1995
Tongue
English
Weight
416 KB
Volume
19
Category
Article
ISSN
0364-9024

No coin nor oath required. For personal study only.

✦ Synopsis


Abstract

We represent a graph by assigning each vertex a finite set such that vertices are adjacent if and only if the corresponding sets have at least two common elements. The 2‐intersection number θ~2~(G) of a graph G is the minimum size of the union of sets in such a representation. We prove that the maximum order of a path that can be represented in this way using t elements is between (t^2^ ‐ 19__t__ + 4)/4 and (t^2^ ‐ t + 6)/4, making θ~2~(P~n~) asymptotic to 2√n. We also show the existence of a constant c depending on ϵ such that, for any tree T with maximum degree at most d, θ~2~(T) ≤ c(√n)^1+ϵ^. When the maximum degree is not bounded, there is an n‐vertex tree T with θ~2~(T) > .945__n__^2/3^. © 1995 John Wiley & Sons, Inc.


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