126. CMB 1998 (vol 41 pp. 488)
 Sun, Heng

Remarks on certain metaplectic groups
We study metaplectic coverings of the adelized group of a split
connected reductive group $G$ over a number field $F$. Assume its
derived group $G'$ is a simply connected simple Chevalley
group. The purpose is to provide some naturally defined sections
for the coverings with good properties which might be helpful when
we carry some explicit calculations in the theory of automorphic
forms on metaplectic groups. Specifically, we
\begin{enumerate}
\item construct metaplectic coverings of $G({\Bbb A})$ from those
of $G'({\Bbb A})$;
\item for any nonarchimedean place $v$, show the section for a
covering of $G(F_{v})$ constructed from a Steinberg section is an
isomorphism, both algebraically and topologically in an open
subgroup of $G(F_{v})$;
\item define a global section which is a product of local sections
on a maximal torus, a unipotent subgroup and a set of
representatives for the Weyl group.
Categories:20G10, 11F75 

127. CMB 1998 (vol 41 pp. 423)
128. CMB 1998 (vol 41 pp. 231)
 Worthington, R. L.

The growth series of compact hyperbolic Coxeter groups with 4 and 5 generators
The growth series of compact hyperbolic Coxeter groups with 4 and 5
generators are explicitly calculated. The assertions of J.~Cannon
and Ph.~Wagreich for the 4generated groups, that the poles of the
growth series lie
on the unit circle, with the exception of a single real reciprocal pair of
poles, are verified. We also verify that for the 5generated groups, this
phenomenon fails.
Categories:20F05, 20F55 

129. CMB 1998 (vol 41 pp. 98)
 Papistas, Athanassios I.

Automorphisms of metabelian groups
We investigate the problem of determining when $\IA (F_{n}({\bf A}_{m}{\bf A}))$
is finitely generated for all $n$ and $m$, with $n\geq 2$ and $m\neq 1$. If
$m$ is a nonsquare free integer then $\IA(F_{n}({\bf A}_{m}{\bf A}))$ is not
finitely generated for all $n$ and if $m$ is a square free integer then
$\IA(F_{n}({\bf A}_{m}{\bf A}))$ is finitely generated for all $n$, with
$n\neq 3$, and $\IA(F_{3}({\bf A}_{m}{\bf A}))$ is not finitely generated.
In case $m$ is square free, Bachmuth and Mochizuki claimed in ([7],
Problem 4) that $\TR({\bf A}_{m}{\bf A})$ is $1$ or $4$. We correct their
assertion by proving that $\TR({\bf A}_{m}{\bf A})=\infty $.
Category:20F28 

130. CMB 1998 (vol 41 pp. 109)
 Tahara, KenIchi; Vermani, L. R.; Razdan, Atul

On generalized third dimension subgroups
Let $G$ be any group, and $H$ be a normal subgroup of $G$. Then M.~Hartl
identified the subgroup $G \cap(1+\triangle^3(G)+\triangle(G)\triangle(H))$
of $G$. In this note we give an independent proof of the result of Hartl,
and we identify two subgroups
$G\cap(1+\triangle(H)\triangle(G)\triangle(H)+\triangle([H,G])\triangle(H))$,
$G\cap(1+\triangle^2(G)\triangle(H)+\triangle(K)\triangle(H))$ of $G$ for
some subgroup $K$ of $G$ containing $[H,G]$.
Categories:20C07, 16S34 

131. CMB 1998 (vol 41 pp. 65)
 Mohammadi Hassanabadi, A.; Rhemtulla, Akbar

Criteria for commutativity in large groups
In this paper we prove the following:
1.~~Let $m\ge 2$, $n\ge 1$ be integers and let $G$ be a group such
that $(XY)^n = (YX)^n$ for all subsets $X,Y$ of size $m$ in $G$. Then
\item{a)} $G$ is abelian or a $\BFC$group of finite exponent bounded by
a function of $m$ and $n$.
\item{b)} If $m\ge n$ then $G$ is abelian or $G$
is bounded by a function of $m$ and $n$.
2.~~The only nonabelian group $G$ such that $(XY)^2 = (YX)^2$ for
all subsets $X,Y$ of size $2$ in $G$ is the quaternion group of order $8$.
3.~~Let $m$, $n$ be positive integers and $G$ a group such that
$$
X_1\cdots X_n\subseteq \bigcup_{\sigma \in S_n\bs 1} X_{\sigma (1)}
\cdots X_{\sigma (n)}
$$
for all subsets $X_i$ of size $m$ in $G$. Then $G$ is
$n$permutable or $G$ is bounded by a function of $m$
and $n$.
Categories:20E34, 20F24 

132. CMB 1997 (vol 40 pp. 330)
 Kapovich, Ilya

Amalgamated products and the Howson property
We show that if $A$ is a torsionfree word hyperbolic group
which belongs to class $(Q)$, that is all finitely generated subgroups of $A$
are quasiconvex in $A$, then any maximal cyclic subgroup $U$ of $A$ is a Burns
subgroup of $A$. This, in particular, implies that if $B$ is a Howson group
(that is the intersection of any two finitely generated subgroups is finitely
generated) then $A\ast_U B$, $\langle A,t \mid U^t=V\rangle$ are also Howson
groups. Finitely generated free groups, fundamental groups of closed
hyperbolic surfaces and some interesting $3$manifold groups are known to
belong to class $(Q)$ and our theorem applies to them. We also describe a
large class of word hyperbolic groups which are not Howson.
Categories:20E06, 20E07, 20F32 

133. CMB 1997 (vol 40 pp. 352)
 Liriano, Sal

A New Proof of a Theorem of Magnus
Using naive algebraic geometric methods a new proof of the
following celebrated theorem of Magnus is given:
Let $G$ be a group with a presentation having $n$ generators and $m$
relations. If $G$ also has a presentation on $nm$ generators, then
$G$ is free of rank $nm$.
Categories:20E05, 20C99, 14Q99 

134. CMB 1997 (vol 40 pp. 341)
 Lee, HyangSook

The stable and unstable types of classifying spaces
The main purpose of this paper is to study groups $G_1$, $G_2$ such that
$H^\ast(BG_1,{\bf Z}/p)$ is isomorphic to $H^\ast(BG_2,{\bf Z}/p)$
in ${\cal U}$, the category of unstable modules over the Steenrod algebra
${\cal A}$, but not isomorphic as graded algebras over ${\bf Z}/p$.
Categories:55R35, 20J06 

135. CMB 1997 (vol 40 pp. 266)
136. CMB 1997 (vol 40 pp. 47)
 Hartl, Manfred

A universal coefficient decomposition for subgroups induced by submodules of group algebras
Dimension subgroups and Lie dimension subgroups are known to satisfy a
`universal coefficient decomposition', {\it i.e.} their value with respect to
an arbitrary coefficient ring can be described in terms of their values with
respect to the `universal' coefficient rings given by the cyclic groups of
infinite and prime power order. Here this fact is generalized to much more
general types of induced subgroups, notably covering Fox subgroups and
relative dimension subgroups with respect to group algebra filtrations
induced by arbitrary $N$series, as well as certain common generalisations
of these which occur in the study of the former. This result relies on an
extension of the principal universal coefficient decomposition theorem on
polynomial ideals (due to Passi, Parmenter and Seghal), to all additive
subgroups of group rings. This is possible by using homological instead
of ring theoretical methods.
Keywords:induced subgroups, group algebras, Fox subgroups, relative dimension, subgroups, polynomial ideals Categories:20C07, 16A27 
