Title
Traces of uniform families of sets
Abstract
The trace of a set F on a another set X is F vertical bar(X) = F boolean AND X and the trace of a family F of sets on X is F(X) = {F vertical bar(X) : F is an element of F}. In this note we prove that if a k-uniform family F subset of (([n])(k)) has the property that for any k-subset X the trace F vertical bar(X) does not contain a maximal chain (a family C(0) subset of C(1) subset of ... subset of C(k) with vertical bar C(i)vertical bar = i), then vertical bar F vertical bar <= ((n-1)(k-1)). This bound is sharp as shown by {F is an element of (([n])(k)), 1 is an element of F}. Our proof gives also the stability of the external family.
Year
Venue
Field
2009
ELECTRONIC JOURNAL OF COMBINATORICS
Discrete mathematics,Combinatorics,Mathematics
DocType
Volume
Issue
Journal
16.0
1.0
ISSN
Citations 
PageRank 
1077-8926
3
0.55
References 
Authors
6
1
Name
Order
Citations
PageRank
Balázs Patkós18521.60