$
\let\vuoto\varnothing
\let\setminus\smallsetminus
\let\iso\simeq
\let\n\triangleleft
\let\implica\Rightarrow
\let\Implica\Longrightarrow
\let\shiff\Leftrightarrow
\let\immersione\hookrightarrow
\let\epi\twoheadrightarrow
\let\mono\rightarrowtail
\let\ot\otimes
\newcommand\set[1]{\{#1\}}
\newcommand\P{{\mathscr P}}
\newcommand\U{{\mathscr U}}
\newcommand\I{{\mathcal I}}
\newcommand\F{{\mathcal F}}
% \newcommand\Pf{{\P_{\mbox{\small\textbf {fin}}}}}
\newcommand\Pf{{\P_{\text{fin}}}}
\newcommand\N{\mathbb N}
\newcommand\Z{\mathbb Z}
\newcommand\Q{\mathbb Q}
\newcommand\R{\mathbb R}
\newcommand\C{\mathbb C}
\newcommand\S{\mathbb S}
\newcommand\Pr{\mathbb P}
\newcommand\ds{\mathbin{\scriptstyle\triangle}}
\newcommand\xor{\mathbin{\mathsf{XOR}}}
\newcommand\nor{\mathbin{\mathsf{NOR}}}
\newcommand\nand{\mathbin{\mathsf{NAND}}}
\newcommand\gen[1]{\langle#1\rangle}
\DeclareMathOperator{\id}{id}
\DeclareMathOperator{\im}{im}
\DeclareMathOperator{\rest}{rest}
\DeclareMathOperator{\Sym}{Sym}
\DeclareMathOperator{\Div}{Div}
\DeclareMathOperator{\Corr}{Corr}
\DeclareMathOperator{\Rel}{Rel}
\DeclareMathOperator{\Map}{Map}
\DeclareMathOperator{\Eq}{Eq}
\DeclareMathOperator{\Part}{Part}
\DeclareMathOperator{\partz}{Partz}
\DeclareMathOperator{\OS}{OS}
\DeclareMathOperator{\OL}{OL}
\DeclareMathOperator{\End}{End}
\DeclareMathOperator{\Hom}{Hom}
\DeclareMathOperator{\jac}{Jac}
\DeclareMathOperator{\nrad}{NilRad}
\DeclareMathOperator{\ann}{Ann}
\DeclareMathOperator{\ass}{Ass}
\DeclareMathOperator{\Min}{Min}
\DeclareMathOperator{\minor}{Minor}
\DeclareMathOperator{\maggior}{Maggior}
\DeclareMathOperator{\var}{Var}
\DeclareMathOperator{\spec}{Spec}
\DeclareMathOperator{\car}{char}
\DeclareMathOperator{\cd}{cd}
\newcommand\Mod{{\mathcal{Mod}}}
% \DeclareRobustCommand {\modbin}{\mathbin{\textrm {mod}}}
\newcommand\modbin {\mathbin{\textrm {mod}}}
\newcommand\antivec[2] {#1^{\raise #2pt\hbox{$\!\!\scriptstyle\leftarrow\!\!$}}}
\newcommand\antivecf{\antivec f3}
\newcommand\antivecv{v^{\raise 1.2pt\hbox{$\!\!\!\scriptstyle\leftarrow\!\!$}}}
\newcommand\antivecg{g^{\raise 2pt\hbox{$\!\!\!\scriptstyle\leftarrow\!\!$}}}
\newcommand\vecvuoto {\vec{\phantom{p}}}
\newcommand\antivecvuoto{\,\antivec {{}}{2}}
% \newcommand\antivecvuoto{{}^{\raise 2pt\hbox{$\scriptstyle\leftarrow\!\!$}}}
\newcommand\maxid{\mathbin{{\n}{\cdot}}}
\let\sseq\subseteq
$
Abstract
We characterise groups in which every abelian subgroup has finite index in its characteristic closure. In a
group with this property every subgroup $H$ has finite index in its characteristic closure and there
is an upper bound
for this index over all subgroups $H$ of $G$. For every prime $p$
we construct groups $G$ with this property that are infinite
nilpotent $p$-groups of class 2 and exponent $p^2$ in
which $G'=Z(G)$ is finite and
$\mathop{Aut} G$ acts trivially on $G/G'$.
We also characterise abelian groups with the dual property that every subgroup has finite index over its characteristic
core.
Dismiss