Monadic n$\times$m-valued Lukasiewicz-Moisil algebras
  Here we initiate an investigation into the class mLMn{\times}m of monadic n{\times}m-valued Lukasiewicz-Moisil algebras (or mLMn{\times}m-algebras), namely n{\times}m-valued Lukasiewicz-Moisil algebras endowed with a unary operation called existential quantifier. These algebras constitute a generalization of monadic n-valued Lukasiewicz-Moisil algebras. In this article, the relationship between existential quantifiers and special subalgebras of mLMn{\times}m-algebras is shown. Besides, the congruences on these algebras are determined and subdirectly irreducible algebras are characterized. From this last result it is proved that mLMn{\times}m is a discriminator variety and as a consequence, the principal congruences are characterized. Furthermore, the number of congruences of finite mLMn{\times}m-algebras is computed. In addition, a topological duality for mLMn{\times}m-algebras is described and a characterization of mLMn{\times}m-congruences in terms of special subsets of the associated space is shown. Moreover, the subsets which correspond to principal congruences are determined. Finally, some functional representation theorems for these algebras are given and the relationship between them is pointed out. 
Aldo V. Figallo and Claudia Sanza
math.LO