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A series of nonrepresentable relation algebras is constructed from groups. We use them to prove that there are continuum many subvarieties between the variety of representable relation algebras and the variety of coset relation algebras. We present our main construction in terms of polygroupoids. [ABSTRACT FROM AUTHOR]

The efforts of Mills College to prepare women for mathematics-oriented professional careers are detailed. The program's philosophy and methodology are viewed as useful tools in aiding both sexes in increasing mathematical competence and confidence, and are adaptable to many educational situations. (MP)

A relation algebra is measurable if the identity element is a sum of atoms, and the square x; 1; x of each subidentity atom x is a sum of non-zero functional elements. These functional elements form a group Gx. We prove that a measurable relation algebra in which the groups Gx are all finite and cyclic is completely representable. A structural description of these algebras is also given. [ABSTRACT FROM AUTHOR]

Abstract A relation algebra is called measurable when its identity is the sum of measurable atoms, where an atom is called measurable if its square is the sum of functional elements. In this paper we show that atomic measurable relation algebras have rather strong structural properties: they are constructed from systems of groups, coordinated systems of isomorphisms between quotients of the groups, and systems of cosets that are used to “shift” the operation of relative multiplication. An atomic and complete measurable relation algebra is completely representable if and only if there is a stronger coordination between these isomorphisms induced by a scaffold (the shifting cosets are not needed in this case). We also prove that a measurable relation algebra in which the associated groups are all finite is atomic. [ABSTRACT FROM AUTHOR]

Independence algebras were introduced in the early 1990s by specialists in semigroup theory, as a tool to explain similarities between the transformation monoid on a set and the endomorphism monoid of a vector space. It turned out that these algebras had already been defined and studied in the 1960s, under the name of v*-algebras, by specialists in universal algebra (and statistics). Our goal is to complete this picture by discussing how, during the middle period, independence algebras began to play a very important role in logic. [ABSTRACT FROM AUTHOR]

The article presents periodical's author contributors, includes Hajnal Andreka, Istvan Nemeti, and Steven Givant.