We review some applications of Gröbner-Shirshov bases, including PBW theorems, linear bases of free universal algebras, normal forms for groups and semigroups, extensions of groups and algebras, embedding of algebras.

In this article we develop an approach to deformations of the Witt and Virasoro algebras based on σ-derivations. We show that σ-twisted Jacobi type identity holds for generators of such deformations. For the σ-twisted generalization of Lie algebras modeled by this construction, we develop a theory of central extensions. We show that our approach can be used to construct new deformations of Lie ...

We characterize the $C^\star$-algebras for which openness of projections in their second duals is preserved under Murray-von Neumann equivalence. They are precisely extensions annihilator by commutative $C^\star$-algebras. also show that all open.

Disclaimer: This dissertation does not contain plagiarised material; except where otherwise stated all theorems are the author's. Acknowledgement: Many thanks to Joel Feinstein for guidance with the literature, useful suggestions and comments on this work.

In this chapter, we adopt Probabilistic Transition Systems as a basic model for probabilistic processes, in which probabilistic and nondeter-ministic choices are independent concepts. The model is essentially a nondeterministic version of Markov decision processes or probabilistic automata of Rabin. We develop a general framework to deene proba-bilistic process languages to describe probabilist...

In this paper we define Baer BL-algebras as BL-algebras with the property that co-annihilator filters are generated by central elements. We use sheaf-theoretic techniques to construct a Baer extension of any BLalgebra, that is to embed any nontrivial BL-algebra A into a Baer BLalgebra A∗. The embedding turns to be an isomorphism if A is itself a Baer BL-algebra. 2000 MSC: 08A72, 03G25, 54B40, 0...

In a series of papers [2, 3, 4, 5], B. Efimov has given sufficient conditions for a Boolean algebra to have a free subalgebra of given cardinality. For example, he has shown that if an infinite Boolean algebra A has cardinality greater than exp exp exp v, but the supremum of the cardinalities of subsets of disjoint elements in A is not greater than v, then A has a free subalgebra with (exp v) i...

This paper completes the classification of central extensions of three dimensional Artin-Schelter regular algebras to four dimensional Artin-Schelter regular algebras. Let A be an AS regular algebra of global dimension three and let D be an extension of A by a central graded element z, i.e. D/〈z〉 = A. If A is generated by elements of degree one, those algebras D which are again AS regular have ...