Основні поняття
This paper presents a topological and algebraic framework for studying polymorphisms and invariant relations of infinite arity (ω-operations and ω-relations). It introduces parametric topologies on the set of ω-operations and uses them to define ω-polymorphisms and ω-invariant relations. The authors characterize the closed ω-clones in terms of ω-polymorphisms and ω-invariant relations, and relate the Inv-Pol Galois connection for finite arity to the Invω-Polω connection for infinite arity.
Анотація
The paper explores new topological and algebraic approaches to the study of clones of operations of infinite arity (ω-operations) and their corresponding invariant relations (ω-relations).
Key highlights:
- The authors introduce the concept of an X-topology on the set of ω-operations, where X is a Boolean ideal on Aω. This generalizes the well-known topology of pointwise convergence.
- They define the notions of X-polymorphism and X-invariant relation, which are parametrized by the ideal X.
- It is shown that the X-closed ω-clones are precisely those that are equal to the set of ω-polymorphisms of their X-invariant relations.
- The authors relate the classical Inv-Pol Galois connection for finite arity to the Invω-Polω connection for infinite arity.
- Several examples of X-topologies are provided, including the local, global, trace, and uniform topologies on ω-operations.
- It is proved that the local, global, trace and uniform closures of an ω-clone are all ω-clones, while for infinitary ω-clones this holds only for the local and global topologies.
The paper provides a comprehensive topological and algebraic framework for understanding clones and polymorphisms of infinite arity, with applications in areas like constraint satisfaction problems.