Embedding lattices in lattices of varieties of groups
M. I. Anokhin M. V. Lomonosov Moscow State University
Abstract:
If
$\mathfrak V$ is a variety of groups and
$\mathfrak U$ is a subvariety, then the symbol
$\langle\mathfrak U,\mathfrak V\rangle$ denotes the complete lattice of
varieties
$\mathfrak X$ such that $\mathfrak U\subseteq \mathfrak X\subseteq \mathfrak V$. Let
$\Lambda=\mathrm C\prod_{n=1}^\infty\Lambda_n$, where
$\Lambda_n$ is the lattice of subspaces of the
$n$-dimensional vector space over the field of two elements, and let
$\mathrm C\prod$ be the Cartesian product operation. A non-empty subset
$K$ of a complete lattice
$M$ is called
a complete sublattice of
$M$ if
$\sup_MX\in K$ and
$\inf_MX\in K$ for any non-empty
$X\subseteq K$.
We prove that
$\Lambda$ is isomorphic to a complete sublattice of
$\langle\mathfrak A_2^4,
\mathfrak A_2^5\rangle$. On the other hand, it is obvious that
$\langle\mathfrak U,\mathfrak A_2\mathfrak U\rangle$ is isomorphic to a complete sublattice of
$\Lambda$ for any locally finite variety
$\mathfrak U$. We deduce criteria for the existence of an isomorphism onto a (complete) sublattice of
$\langle\mathfrak U,\mathfrak A_2\mathfrak U\rangle$ for some locally finite variety
$\mathfrak U$. We also prove that there is a sublattice
$\langle\mathfrak A_2^4,\mathfrak A_2^5\rangle$ generated by four elements and containing an infinite chain.
MSC: 20E10,
20F16,
08B15,
20F05 Received: 09.06.1997
DOI:
10.4213/im250