From the 1 of 5 linked papers with an AI index.
5 papers
Two generalisations of sharp k-transitivity
J. de la Nuez González, Rob Sullivan
The paper introduces two extensions of sharply k‑transitive group actions—one based on subgroups of the symmetric group and another on relational structures—and determines when suc…
Structured sunflowers and canonical Ramsey properties
Rob Sullivan, Jeroen Winkel
A first-order structure is said to have the infinite sunflower property if, for each and each structure whose elements are -sets, there is…
Group-extensive embeddings into Fraïssé structures and stationary weak independence relations
Aleksandra Kwiatkowska, Rob Sullivan, Jeroen Winkel
Let be a Fraïssé structure (a countably infinite ultrahomogeneous structure). We call an embedding group-extensive if each automorphism of its image extends to an…
Embeddings into the generic poset
Aleksandra Kwiatkowska, Rob Sullivan, Jeroen Winkel
Let M be the generic poset, defined as the Fraïssé limit of the class of finite posets. We show that every countably infinite poset A can be embedded with coinfinite image into M…
The externally definable Ramsey property and fixed points on type spaces
Nadav Meir, Rob Sullivan
We discuss the externally definable Ramsey property, a weakening of the Ramsey property for ultrahomogeneous structures, where the only colourings considered are those that are ext…