In this paper we study the category of hyper MV-algebras and we prove that it has a terminal object and a coequalizer. We show that Jia's construction can be modified to provide a free hyper MV-algebra by a set. We use this to show that in the category of hyper MV-algebras the monomorphisms are exactly the one-to-one homomorphisms.

In this paper we define the hyper operations ⊗, ∨ and ∧ on a hyper MV -algebra and we obtain some related results. After that by considering the notions ofhyper MV -ideals and weak hyper MV -ideals, we prove some theorems. Then we determine relationships between hyper MV -ideals in a hyper MV -algebra and hyper K -ideals in a hyper K -algebra . Finally we give a characterization of hyper MV -algebras (...) of order 3 or 4 based on the hyper MV -ideals. (shrink)

The notions of a hyper MV-deductive system, a -hyper MV-deductive system, a - hyper MV-deductive system, a -hyper MV-deductive system, a -hyper MV-deductive system and a -hyper MV-deductive system are introduced, and then their relations are investigated.

Generalizations of Boolean elements of a BL-algebra L are studied. By utilizing the MV-center MV(L) of L, it is reproved that an element x L is Boolean iff x x * = 1. L is called semi-Boolean if for all x L, x * is Boolean. An MV-algebra L is semi-Boolean iff L is a Boolean algebra. A BL-algebra L is semi-Boolean iff L is an SBL-algebra. A BL-algebra L is called hyper-Archimedean if for all x L, xn is (...) Boolean for some finite n 1. It is proved that hyper-Archimedean BL-algebras are MV-algebras. The study has application in mathematical fuzzy logics whose Lindenbaum algebras are MV-algebras or BL-algebras. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). (shrink)