a1 Universität Frankfurt am Main, West Germany
Arithmetic subgroups of reductive algebraic groups over number fields are finitely presentable, but over global function fields this is not always true. All known exceptions are “small” groups, which means that either the rank of the algebraic group or the set S of the underlying S-arithmetic ring has to be small. There exists now a complete list of all such groups which are not finitely generated, whereas we onlyhave a conjecture which groups are finitely generated but not finitely presented.
(Received August 10 1985)
* This paper forms part of the Proceedings of the conference Groups–St Andrews 1985.