In the paper, we introduce 𝔏-fuzzy state filters in state residuated lattices and investigate their related properties, where 𝔏 is a complete Heyting algebra. Moreover, we study the 𝔏-fuzzy state co-annihilator of an 𝔏-fuzzy set with respect to an 𝔏-fuzzy state filter. Finally, using the 𝔏-fuzzy state co-annihilator, we investigate lattice structures of the set of some types of 𝔏-fuzzy state filters in state residuated lattices. In particular, we prove that: (1) the set FSF[L] of all 𝔏-fuzzy state filters is a complete Heyting algebra; (2) the set S_νFSF[L] of all stable state filters relative to an 𝔏-fuzzy set ν is also a complete Heyting algebra; (3) the set I_μFSF[L] of all involutory 𝔏-fuzzy state filters relative to an 𝔏-fuzzy state filter μ is a complete Boolean algebra.

This paper introduces the implicative derivations and gives some of their characterizations on MTL-algebras. Furthermore, we provide some representation of MTL-algebras by implicative derivations and obtain some representation of Boolean algebra via the algebra of all implicative derivations. Finally, we explore the relationship between implicative derivation and other operators on MTL-algebras and show that there exists a bijection between the sets of multiplier and implicative derivations on IMTL-algebras. The results of this paper can provide the common properties of implicative derivations in the t-norm-based fuzzy logical algebras.

P. Hájek introduced an S5-like modal fuzzy logic S5(BL) and showed that is equivalent to the monadic basic predicate logic mBL_∀. Inspired by the above important results, D. Castaño et al. introduced monadic BL-algebras and their corresponding propositional logic S5’(BL), which is a simplified set of axioms of S5(BL). In this paper, we review the algebraic semantics of S5’(BL) and obtain some new results regarding to monadic BL-algebras. First we recall that S5’(BL) is completeness with respect to the variety 𝕄𝔹𝕃 of monadic BL-algebras and obtain a necessary and sufficient condition for the logic S5’(BL) to be semilinear. Then we study some further algebraic properties of monadic BL-algebras and discuss the relationship between monadic MV-algebras and monadic BL-algebras. Finally we give some characterizations of representable, simple, semisimple and directly indecomposable monadic BL-algebras, which are important members of the variety 𝕄𝔹𝕃. These results also constitute a crucial first step for providing an equivalent algebraic foundation for mBL_∀.