Let D be a t- (v, k,k) design and let N i (D), for 1 β€ i β€ t, be the higher incidence matrix of D, a (0, 1)-matrix of size v iΓb , where b is the number of blocks of D. A zero-sum flow of D is a nowhere-zero real vector in the null space of N 1 (D). A zero-sum k-flow of D is a zero-sum flow with val
Zero-sum block designs and graph labelings
β Scribed by Zsolt Tuza
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 621 KB
- Volume
- 3
- Category
- Article
- ISSN
- 1063-8539
No coin nor oath required. For personal study only.
β¦ Synopsis
Proving a conjecture of Aigner and Triesch, we show that every graph G = (V,E) without isolated vertices and isolated edges admits an edge labeling 5: E -{0,1}" with binary vectors of length m = [log2 nl + 1 such that the sums 6 ( v ) := 1 ; ; ; &(e) (taken modulo 2 componentwise) are mutually distinct, provided that n is sufficiently large. The proof combines probabilistic arguments with explicitly constructed Steiner systems.
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A main result proved in this paper is the following. Theorem. Let G be a noncomplete graph on n vertices with degree sequence where R is the zero-sum Ramsey number.
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Consider the maximum length [(k) of a flexicographieally) increasing sequence of vectors in GF(2) k with the property that the sum of the vectors in any consecutive subsequence is nonzero modulo 2. We prove that ~. 2 k ~<f(k)~<(~+o(1))2 k. A related problem is the following. Suppose the edges of th
In this article we study the n-existential closure property of the block intersection graphs of infinite t-(v, k, k) designs for which the block size k and the index k are both finite. We show that such block intersection graphs are 2-e.c. when 2 β€ t β€ k-1. When k = 1 and 2 β€ t β€ k, then a necessary