Stephen H. Hechler

Learn More
Define a simple graph G to be k-superuniversal iff for any k-element simple graph K and for any full subgraph H of K every full embedding of H into G can be extended to a full embedding of K into G . We prove that for each positive integer k there exist finite k-superuniversal graphs, and we find upper and lower bounds on the smallest such graphs . We also(More)
Recently, R. M. Stephenson has used the Continuum Hypothesis to construct two Ä-closed, separable regular, first countable, noncompact Hausdorff spaces. We show that the assumption of the Continuum Hypothesis can be removed by replacing a lemma used in the original construction to deal with arbitrary almost-disjoint families by the construction of a(More)
In his paper on subsets of the series of natural numbers N. Lusin [2] defines two sets F, G g co to be orthogonal (F I G) iff F c3 G is finite. A family (henceforth the term family will be used only to denote subsets of the power set of co) is said to be internally orthogonal iff for any two distinct members F, G of ~ we have F 2. G. Two families ~ and ~(More)
  • 1