Poly-nilpotent group
A group possessing a finite normal series with nilpotent factors; such a series is called poly-nilpotent. The length of the shortest poly-nilpotent series of a poly-nilpotent group is called its poly-nilpotent length. The class of all poly-nilpotent groups coincides with the class of all solvable groups (cf. Solvable group); however, in general the poly-nilpotent length is less than the solvable length. A poly-nilpotent group of length 2 is called meta-nilpotent.
All groups having (an increasing) poly-nilpotent series of length $l$ whose factors in increasing order have nilpotent classes not exceeding the numbers $c_1,\dots,c_l$, respectively, form a variety $\mathfrak M$, which is the product of nilpotent varieties:
$$\mathfrak M=\mathfrak N_{c_1}\dots\mathfrak N_{c_l}$$
(see Variety of groups). The free groups of such a variety are called free poly-nilpotent groups. Of particular interest are the varieties $\mathfrak N_c\mathfrak A$ and $\mathfrak A\mathfrak N_c$. The first of them contains all connected solvable Lie groups; in the second, all finitely-generated groups are finitely approximable and satisfy the maximum condition for normal subgroups.
References
[1] | A.G. Kurosh, "The theory of groups" , 1–2 , Chelsea (1960) (Translated from Russian) |
[2] | H. Neumann, "Varieties of groups" , Springer (1967) |
Poly-nilpotent group. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Poly-nilpotent_group&oldid=19220