Monadic BL-algebras: the equivalent algebraic semantics of Hájek's monadic fuzzy logic (Q1697516)

The authors introduce the variety of monadic BL-algebras as BL-algebras endowed with two monadic operators \(\forall\) and \(\exists\). After a study of the basic properties of this variety, they show that this class is the equivalent algebraic semantics of the monadic fragment of Hájek's basic predicate logic. In addition, they start a systematic study of the main subvarieties of monadic BL-algebras, some of which constitute the algebraic semantics of well-known monadic logics: monadic Gödel logic and monadic Łukasiewicz logic. Finally, a complete characterization of totally ordered monadic BL-algebras is given.