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A locally cyclic group is a group in which each finitely generated subgroup is cyclic. An example is the additive group of the rational numbers: every finite set of rational numbers is a set of integer multiples of a single unit fraction, the inverse of their lowest common denominator, and generates as a subgroup a cyclic group of integer ...
The lattice of subgroups of the infinite cyclic group can be described in the same way, as the dual of the divisibility lattice of all positive integers. If the infinite cyclic group is represented as the additive group on the integers, then the subgroup generated by d is a subgroup of the subgroup generated by e if and only if e is a divisor ...
A proper subgroup of a group G is a subgroup H which is a proper subset of G (that is, H ≠ G). This is often represented notationally by H < G, read as "H is a proper subgroup of G". Some authors also exclude the trivial group from being proper (that is, H ≠ {e} ). [2] [3] If H is a subgroup of G, then G is sometimes called an overgroup of H.
The additive group of rational numbers (Q, +) is locally cyclic – any pair of rational numbers a/b and c/d is contained in the cyclic subgroup generated by 1/(bd). [2]The additive group of the dyadic rational numbers, the rational numbers of the form a/2 b, is also locally cyclic – any pair of dyadic rational numbers a/2 b and c/2 d is contained in the cyclic subgroup generated by 1/2 max ...
For example, Z no longer qualifies, since one has [0, n, −1] for every n. As a corollary to Świerczkowski's proof, every Archimedean cyclically ordered group is a subgroup of T itself. [ 3 ] This result is analogous to Otto Hölder 's 1901 theorem that every Archimedean linearly ordered group is a subgroup of R .
Example subgroups from a hexagonal dihedral symmetry. D 1 is isomorphic to Z 2, the cyclic group of order 2. D 2 is isomorphic to K 4, the Klein four-group. D 1 and D 2 are exceptional in that: D 1 and D 2 are the only abelian dihedral groups. Otherwise, D n is non-abelian. D n is a subgroup of the symmetric group S n for n ≥ 3.
Since for any n ≥ 2, the free group on 2 generators F 2 contains the free group on n generators F n as a subgroup of finite index (in fact n − 1), once one non-cyclic free group on finitely many generators is known to be not boundedly generated, this will be true for all of them.
In mathematics, especially in the area of algebra known as group theory, the term Z-group refers to a number of distinct types of groups: in the study of finite groups, a Z-group is a finite group whose Sylow subgroups are all cyclic. in the study of infinite groups, a Z-group is a group which possesses a very general form of central series.