If K = Goφ Z where φ is a tame automorphism of the 1-relator group G, then the combinatorial area of loops in a Cayley graph of G is undistorted in a Cayley graph of K. Examples of distortion of area in fibres of fibrations over the circle are given and a notion of exponent of area distortion is introduced and studied. The inclusion of a finitely generated abelian subgroup in the fundamental gr...

We give a general procedure to construct a certain class of ”quandle-like” structures from an arbitrary group. These structures, which we refer to as pseudoquandles, possess two of the three defining properties of quandles. We classify all pseudoquandles obtained from an arbitrary finitely generated abelian group. We also define the notion of the kernel of an element of a pseudoquandle and prov...

Practical methods for computing equivalent forms of integer matrices are presented. Both heuristic and modular techniques are used to overcome integer overflow problems, and have successfully handled matrices with hundreds of rows and columns. Applications to finding the structure of finitely presented abe!Jan groups are described. I . Introduction The theory of finitely generated abelian group...

This note records some observations concerning geodesic growth functions. If a nilpotent group is not virtually cyclic then it has exponential geodesic growth with respect to all finite generating sets. On the other hand, if a finitely generated group G has an element whose normal closure is abelian and of finite index, then G has a finite generating set with respect to which the geodesic growt...

We collect in this paper some remarks and observations about limit groups of equationally noetherian groups. We show in particular, that some known properties of limit groups of a free group or, more generally, of a torsion-free hyperbolic group can be seen as consequences of the fact that such groups are equationally noetherian. Especially, such properties are still true for linear groups and ...

Tits has shown that a finitely generated matrix group either contains a nonabelian free group or has a solvable subgroup of finite index. We give a polynomial time algorithm for deciding which of these two conditions holds for a given finitely generated matrix group over an algebraic number field. Noting that many computational problems are undecidable for groups with nonabelian free subgroups,...

We study periodic rings that are finitely generated as groups. We prove several structure results. We classify periodic rings that are free of rank at most 2, and also periodic rings R such that R is finitely generated as a group and R/t(R) Z. In this way, we construct new classes of periodic rings. We also ask a question concerning the connection to periodic rings that are finitely generated a...

We introduce a notion of shadowing property for actions of finitely generated groups and study its basic properties. We formulate and prove a shadowing lemma for actions of nilpotent groups. We construct an example of a faithful linear action of a solvable Baumslag-Solitar group and show that the shadowing property depends on quantitative characteristics of hyperbolicity. Finally we show that a...

In the last lecture we proved that the torsion subgroup of the rational points on an elliptic curve E/Q is finite. In this lecture we will prove a special case of Mordell’s theorem, which states that E(Q) is finitely generated. By the structure theorem for finitely generated abelian groups, this implies E(Q) ' Z ⊕ T, where Zr is a free abelian group of rank r, and T is the (necessarily finite) ...