Cyclical elementary nets
N. A. Dzhusoeva,
R. Y. Dryaeva North Ossetian State University after Kosta Levanovich Khetagurov, Vladikavkaz
Abstract:
Let
$R$ be a commutative ring with the unit and
$n\in\mathbb{N}$. A set
$\sigma = (\sigma_{ij})$,
$1\leqslant{i, j} \leqslant{n},$ of additive subgroups of the ring
$R$ is a
net over
$R$ of order
$n$, if $ \sigma_{ir} \sigma_{rj} \subseteq{\sigma_{ij}} $ for all
$1\leqslant i, r, j\leqslant n$. A net which doesn't contain the diagonal is called
an elementary net. An elementary net $\sigma = (\sigma_{ij}), 1\leqslant{i\neq{j} \leqslant{n}}$, is
complemented, if for some additive subgroups
$\sigma_{ii}$ of
$R$ the set $\sigma = (\sigma_{ij}), 1\leqslant{i, j} \leqslant{n}$ is a full net. An elementary net
$\sigma$ is called
closed, if the elementary group $ E(\sigma) = \langle t_{ij}(\alpha) : \alpha\in \sigma_{ij}, 1\leqslant{i\neq{j}} \leqslant{n}\rangle $ doesn't contain elementary transvections. It is proved that the cyclic elementary odd-order nets are complemented. In particular, all such nets are closed. It is also shown that for every odd
$n\in\mathbb{N}$ there exists an elementary cyclic net which is not complemented.
Key words:
intermediate subgroup, non-split maximal torus, net, cyclic net, net group, elementary group, transvection.
UDC:
519.46
Received: 14.03.2016