
doi: 10.1007/bf01787815
A two-fold triple system (TTS) is a 2-\((v,k,2)\) design (and hence \(v \equiv 1\) or \(3 \pmod 6\)). An overlarge set of TTS, denoted by \(\text{OS(TTS} (v))\) is a set of \(v + 1\) mutually disjoint \(\text{TTS} (v)\) (i.e. they have no triple in common), each of them based on a different \(v\)-subset of a set \(X\) of cardinality \(v + 1\). The authors prove that if \(|X |= 7\), then the 84 distinct (but all isomorphic) TTS(6) based on \(X\), can be partitioned into 12 OS(TTS(6)) each containing 7 TTS(6). Moreover there exists a resolution into 84 parallel classes of the set of 1008 distinct OS(TTS(6)) based on \(X\). Using this terminology they revisit the Hoffman-Singleton graph as well as the Higman-Sims graph. They proof, using their terminology, the well-known fact that this last graph is the union of two Hoffman-Singleton graphs. The reviewer disagrees with the authors that their description of the Higman-Sims graph is the first elementary construction.
Higman- Sims graph, Triple systems, Association schemes, strongly regular graphs, triple system, strongly regular graphs, Hoffman-Singleton graph
Higman- Sims graph, Triple systems, Association schemes, strongly regular graphs, triple system, strongly regular graphs, Hoffman-Singleton graph
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 4 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Average | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Average |
