Given a nonempty set L of linear orders, we say that the linear order L is L-convex embeddable into the linear order L′ if it is possible to partition L into convex sets indexed by some element of L which are isomorphic to convex subsets of L′ ordered in the same way. This notion generalizes convex embeddability and (finite) piecewise convex embeddability (both studied in [13]), which are the special cases L={1} and L=Fin. We focus mainly on the behavior of these relations on the set of countable linear orders, first characterizing when they are transitive, and hence a quasi-order. We then study these quasi-orders from a combinatorial point of view, and analyze their complexity with respect to Borel reducibility. Finally, we extend our analysis to uncountable linear orders.
Piecewise convex embeddability on linear orders
Iannella M.;Marcone A.;
2025-01-01
Abstract
Given a nonempty set L of linear orders, we say that the linear order L is L-convex embeddable into the linear order L′ if it is possible to partition L into convex sets indexed by some element of L which are isomorphic to convex subsets of L′ ordered in the same way. This notion generalizes convex embeddability and (finite) piecewise convex embeddability (both studied in [13]), which are the special cases L={1} and L=Fin. We focus mainly on the behavior of these relations on the set of countable linear orders, first characterizing when they are transitive, and hence a quasi-order. We then study these quasi-orders from a combinatorial point of view, and analyze their complexity with respect to Borel reducibility. Finally, we extend our analysis to uncountable linear orders.| File | Dimensione | Formato | |
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20250226 Piecewise embeddability (first revision submitted).pdf
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