Cancellation Theorem Vladimir

Cancellation theorem

A Cancellation Theorem for BCCSP

This paper presents a cancellation theorem for the preorders in van Glabbeek’s linear time-branching time spectrum over BCCSP. Apart from having some intrinsic interest, the proven cancellation result plays a crucial role in the study of the cover equations, in the sense of Fokkink and Nain, that characterize the studied semantics. The techniques used in the proof of the cancellation theorem ma...

On a small cancellation theorem of Gromov

We give a combinatorial proof of a theorem of Gromov, which extends the scope of small cancellation theory to group presentations arising from

Walker's Cancellation Theorem

Walker’s cancellation theorem says that if B Z is isomorphic to C Z in the category of abelian groups, then B is isomorphic to C. We construct an example in a diagram category of abelian groups where the theorem fails. As a consequence, the original theorem does not have a constructive proof even if B and C are subgroups of the free abelian group on two generators. Both of these results contras...

The Equational Theory of Paramedial Cancellation Groupoids

By a paramedial groupoid we mean a groupoid satisfying the equation xy · zu = uy · zx. As it is easy to see, the equational theory of paramedial groupoids, as well as the equational theory based on any balanced equation, is decidable. In this paper we are going to investigate the equational theory of paramedial cancellation groupoids; by this we mean the set of all equations satisfied by parame...