Talk:Subgroup series

Naming: Normal series, subnormal series

I'm using the term subnormal series for $A_{i}\triangleleft A_{i+1}$ and normal series for $A_{i}\triangleleft G$, as I find these clear, and at least some sources Springer Encyclopaedia of Mathematics use this convention. There are visibly other conventions, and if someone more familiar with group theory usage would prefer another, I've no objection.

Nbarth (email) (talk) 00:49, 15 January 2008 (UTC)

On the origin of the naming

The article says "A subnormal series (also normal series, normal tower, subinvariant series, or just series) of a group G is a sequence of subgroups..."

If a normal series is a sequence of subgroups, then why isn't it called a normal sequence? Does anyone where the origin of the name came? It somewhat confuses because usually one uses the term series for the addition of the terms in a sequence, but here there is no addition, just the sequence. — Preceding unsigned comment added by 186.58.65.13 (talk) 19:43, 29 October 2012 (UTC)

Is there an improved concept for subnormal series?

For certain transfinite descending series the definition of subnormal needs to be refined, because there may be no 'next'. Leen Droogendijk (talk) 11:12, 17 February 2013 (UTC)

See descendant subgroup (and ascendant subgroup, for ascending series). Even more general is the concept of a serial subgroup, but we haven't got an article for that yet. --Zundark (talk) 11:52, 17 February 2013 (UTC)