On minimal non-σ-scattered linear orders
We present new constructions of linear orders which are minimal with respect to being non-σ-scattered. Specifically, we will show that Jensen's ♢ principle implies that there is a minimal Countryman line, answering a question of Baumgartner. We will also construct the first consistent examples of minimal non-σ-scattered linear ordersof cardinality greater than ℵ1. In fact this can be achieved at any successor cardinal κ+,both via forcing constructions and via axiomatic principles which hold in G\"odel's Constructible Universe. These linear orders of cardinality κ+ have the property that their square is theunion of κ-many chains. This is joint work with James Cummings and Todd Eisworth.