Title
Large girth approximate Steiner triple systems
Abstract
In 1973, Erdos asked whether there are n-vertex partial Steiner triple systems with arbitrary high girth and quadratically many triples. (Here girth is defined as the smallest integer g > 4 for which some g-element vertex-set contains at least g-2 triples.) We answer this question, by showing existence of approximate Steiner triple systems with arbitrary high girth. More concretely, for any fixed l > 4, we show that a natural constrained random process typically produces a partial Steiner triple system with (1/6-o(1))n2 triples and girth larger than l. The process iteratively adds random triples subject to the constraint that the girth remains larger than l. Our result is best possible up to the o(1)-term, which is a negative power of n.
Year
DOI
Venue
2019
10.1112/jlms.12242
JOURNAL OF THE LONDON MATHEMATICAL SOCIETY-SECOND SERIES
Keywords
Field
DocType
05B07,05C80 (primary),60C05,05B30,60G99 (secondary)
Integer,Topology,Combinatorics,Monad (category theory),Quadratic growth,Random graph,Stochastic process,Probabilistic method,Mathematics,Steiner system
Journal
Volume
Issue
ISSN
100.0
3.0
0024-6107
Citations 
PageRank 
References 
0
0.34
0
Authors
2
Name
Order
Citations
PageRank
Tom Bohman125033.01
Lutz Warnke2196.13