For any continuous self-map of a compact metric space, we prove saturation distributionally scrambled Mycielski sets under type shadowing and the chain transitivity. This extends result J. Li, S. Tu, Devaney chaos plus implies distributional chaos, Chaos 26 (2016), 093103, 6 pp.

Let G be a simple graph with vertex set V (G). The common neighborhood graph or congraph of G, denoted by con(G), is a graph with vertex set V (G), in which two vertices are adjacent if and only if they have at least one common neighbor in G. We compute the congraphs of some composite graphs. Using these results, the congraphs of several special graphs are determined.

In [15], Shelah proclaims the aim of reconstructing model theory, ‘with no use of even traces compactness’. We analyze here one aspect of this program. Keisler organizes [8] around four kinds of constructions: the Henkin method, EhrenfeuchtMostowski models, unions of chains, and ultraproducts. The later history of model theory reveals a plethora of tools arising in stability theory. Fundamental...

A relation R is p-divisible if for any partition of its basis into p + 1 subsets, R is embedded into the union of p of them. We prove that any countable p-divisible relation embeds two copies of itself intersecting in at most p− 1 elements. A relation R is indivisible if for any partition of its set of vertices into two subsets V1 and V2, there exists i ∈ {1, 2} such that R is embedded into R(V...

The most familiar construction of graphs whose clique number is much smaller than their chromatic number is due to Mycielski, who constructed a sequence G n of triangle-free graphs with (G n ) = n. In this note, we calculate the fractional chromatic number of G n and show that this sequence of numbers satis es the unexpected recurrence a n+1 = a n + 1 a n .

Zykov designed one of the oldest known family of triangle-free graphs with arbitrarily high chromatic number. We determine the fractional chromatic number of the Zykov product of a family of graphs. As a corollary, we deduce that the fractional chromatic numbers of the Zykov graphs satisfy the same recurrence relation as those of the Mycielski graphs, that is an+1 = an + 1 an . This solves a co...