Weak direct products of arbitrary universal algebras are introduced. The usual notion for groups and rings is a special case. Some universal algebraic properties are proved and applications to cylindric and polyadic algebras are considered.
Mathematical Institute of the Hungarian Academy of Sciences, Budapest, PF. 127, H-1364, Hungary
Bibliografia
[1] H. Andréka, T. Gergely and I. Németi, Purely algebraic construction of first order logics, preprint of Central Research Institute of Hung. Acad. Sci., Budapest, No. KFKI-73-71 (1973), 46 pp.
[2] H. Andréka, T. Gergely and I. Németi, On universal algebraic construction of logics, Studia Logica 36 (1-2) (1977), 9-47.
[3] H. Andréka and I. Németi, A simple, purely algebraic proof of the completeness of some first order logics, Algebra Universalis 5 (1975), 8-15.
[4] H. Andréka and I. Németi, Formulas and ultraproducts in categories, Beiträge Algebra Geom. 8 (1979), 133-151.
[5] M. A. Arbib and E. G. Manes, Arrows, Structures and Functors: The Categorial Imperative, Academic Press, 1975.
[6] E. K. Van Deuven, J. D. Monk and R. Matatyahu, Some questions about Boolean algebras, preprint, Univ. of Colorado, Boulder, Co., 1979.
[7] S. Eilenberg and M. P. Schützenberger, On pseudovarieties, Adv. in Math. 19 (3) (1976), 413-418.
[8] L. Fuchs, Infinite Abelian Groups, Academic Press, 1970.
[9] S. Givant, The structure of relation algebras generated by relativizations, preprint, Dept. of Math., Mills College, Oakland, Cal., 1991, 152 pp.
[10] G. Grätzer, Universal Algebra, second ed., Springer, Berlin 1979.
[11] L. Henkin, J. D. Monk and A. Tarski, Cylindric Algebras, North-Holland, Amsterdam 1971 and 1985.
[12] L. Henkin, J. D. Monk, A. Tarski, H. Andréka and I. Németi, Cylindric Set Algebras, Lecture Notes in Math. 883, Springer, Berlin 1981.
[13] I. Malcev, Algebraic Systems, Akademie-Verlag, Berlin 1973.
[14] J. D. Monk, Mathematical Logic, Graduate Texts in Math. 37, Springer, Berlin 1978.
[15] J. D. Monk, On depth of Boolean algebras, lecture at the Math. Inst. Hungar. Acad. Sci., Budapest, December 1978.
[16] J. D. Monk and R. Bonnet (eds.), Handbook of Boolean Algebras, I-II-III, North-Holland, Amsterdam 1989.
[17] I. Németi, Connections between cylindric algebras and initial algebra semantics of CF languages, in: Mathematical Logic in Computer Science (Proc. Coll. Salgótarján 1978), B. Dömölki and T. Gergely (eds.), Colloq. Math. Soc. J. Bolyai 26, North-Holland, Amsterdam 1981, 561-605.
[18] I. Németi and I. Sain, Cone-implicational subcategories and some Birkhoff-type theorems, in: Universal Algebra (Proc. Coll. Esztergom 1977), Colloq. Math. Soc. J. Bolyai 29, North-Holland, Amsterdam 1982, 535-578.
[19] D. Pigozzi, On some operations on classes of algebras, Algebra Universalis 2 (1972), 346-353.