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Common group names: Z n: the cyclic group of order n (the notation C n is also used; it is isomorphic to the additive group of Z / nZ) Dih n: the dihedral group of order 2 n (often the notation D n or D 2n is used) K 4: the Klein four-group of order 4, same as Z2 × Z2 and Dih 2. D 2n: the dihedral group of order 2 n, the same as Dih n ...
Abelian group. In mathematics, an abelian group, also called a commutative group, is a group in which the result of applying the group operation to two group elements does not depend on the order in which they are written. That is, the group operation is commutative. With addition as an operation, the integers and the real numbers form abelian ...
In mathematics, specifically in group theory, an elementary abelian group is an abelian group in which all elements other than the identity have the same order. This common order must be a prime number, and the elementary abelian groups in which the common order is p are a particular kind of p -group. [1][2] A group for which p = 2 (that is, an ...
The group {1, −1} above and the cyclic group of order 3 under ordinary multiplication are both examples of abelian groups, and inspection of the symmetry of their Cayley tables verifies this. In contrast, the smallest non-abelian group, the dihedral group of order 6, does not have a symmetric Cayley table.
It is, however, an abelian group, and isomorphic to the dihedral group of order (cardinality) 4, symbolized (or , using the geometric convention); other than the group of order 2, it is the only dihedral group that is abelian. The Klein four-group is also isomorphic to the direct sum, so that it can be represented as the pairs {(0,0), (0,1), (1 ...
Order and structure. The order of a group G and the orders of its elements give much information about the structure of the group. Roughly speaking, the more complicated the factorization of | G |, the more complicated the structure of G. For | G | = 1, the group is trivial. In any group, only the identity element a = e has ord (a) = 1.
Stated differently the fundamental theorem says that a finitely generated abelian group is the direct sum of a free abelian group of finite rank and a finite abelian group, each of those being unique up to isomorphism. The finite abelian group is just the torsion subgroup of G. The rank of G is defined as the rank of the torsion-free part of G ...
Ab is a full subcategory of Grp, the category of all groups. The main difference between Ab and Grp is that the sum of two homomorphisms f and g between abelian groups is again a group homomorphism: The third equality requires the group to be abelian. This addition of morphism turns Ab into a preadditive category, and because the direct sum of ...