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Lattices of Interpretability Types of Varieties
D. M. Smirnov
Abstract:
Let
$\Pi$ be the set of all primes,
$\mathbb A$ the field of all algebraic numbers, and
$Z$ the set of square-free natural numbers. We consider partially ordered sets of interpretability types such as
$$
\mathbb L_\Pi=(\{[AD_\Gamma]\mid\Gamma\subseteq\Pi\},\le),
\qquad \mathbb L_\mathbb A=(\{[M_\mathbb K]\mid\mathbb K\subseteq\mathbb A\},\le),
$$
and
$$
\mathbb L_Z=(\{[G_n]\mid n\in Z\},\le),
$$
where
$AD_\Gamma$ is a variety of
$\Gamma$-divisible Abelian groups with unique taking of the
$p$th root
$\xi_p(x)$ for every
$p\in\Gamma$,
$M_\mathbb K$ is a variety of
$\mathbb K$-modules over a normal field
$\mathbb K$, contained in
$\mathbb A$, and
$G_n$ is a variety of
$n$-groupoids defined by a cyclic permutation
$(12\ldots n)$. We prove that
$\mathbb L_\Pi$,
$\mathbb L_\mathbb A$, and
$\mathbb L_Z$ are distributive lattices, with $\mathbb L_\Pi\cong \mathbb L_\mathbb A\cong \mathbb S\rm ub\,\Pi$ and
$\mathbb L_Z\cong \mathbb S\rm ub_f\Pi$ where
$\mathbb S\rm ub\,\Pi$ and
$\mathbb S\rm ub_f\Pi$ are lattices (w. r. t. inclusion) of all subsets of the set
$\Pi$ and of finite subsets of
$\Pi$, respectively.
Keywords:
interpretability type, variety, $\Gamma$-divisible Abelian group, module over a normal field, $n$-groupoid.
UDC:
512.572 Received: 14.04.2004