-Hamiltonian and -regular algebraic structures
The concept of a -closed subset was introduced in [1] for an algebraic structure of type and a set of open formulas of the first order language . The set of all -closed subsets of forms a complete lattice whose properties were investigated in [1] and [2]. An algebraic structure is called - hamiltonian, if every non-empty -closed subset of is a class (block) of some congruence on ; is called - regular, if for every two , whenever they have a congruence class in common....