| Popis: |
In this note we introduce the notion of a transcendental group, that is, a subgroup $G$ of the topological group $\mathbb{C}$ of all complex numbers such that every element of $G$ except $ 0$ is a transcendental number. All such topological groups are separable metrizable zero-dimensional torsion-free abelian groups. Further, each transcendental group is homeomorphic to a subspace of $\mathbb{N}^{\aleph_0}$, where $\mathbb{N}$ denotes the discrete space of natural numbers. It is shown that (i) each countably infinite transcendental group is a member of one of three classes, where each class has $\mathfrak{c}$ (the cardinality of the continuum) members -- the first class consists of those isomorphic as a topological group to the discrete group $\ZZ$ of integers, the second class consists of those isomorphic as a topological group to $\ZZ\times \ZZ$, and the third class consists of those homeomorphic to the topological space $\QQ$ of all rational numbers; (ii) for each cardinal number $\aleph$ with $\aleph_0< \aleph\le \cc$, there exist $2^\aleph$ transcendental groups of cardinality $\aleph$ such that no two of the transcendental groups are isomorphic as topological groups or even homeomorphic; (iii) there exist $\mathfrak{c}$ countably infinite transcendental groups each of which is homeomorphic to $\QQ$ and algebraically isomorphic to a vector space over the field $\AAA$ of all algebraic numbers (and hence also over $\QQ$) of countably infinite dimension; (iv) $\RR$ has $2^\cc$ transcendental subgroups, each being a zero-dimensional metrizable torsion-free abelian group, such that no two of the transcendental groups are isomorphic as topological groups or even homeomorphic. |
