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e. In mathematics, specifically group theory, Cauchy's theorem states that if G is a finite group and p is a prime number dividing the order of G (the number of elements in G), then G contains an element of order p. That is, there is x in G such that p is the smallest positive integer with xp = e, where e is the identity element of G.
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 ...
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 ...
More generally, G is called the direct sum of a finite set of subgroups {Hi} if. G = {Hi} ; in other words, G is generated by the subgroups {Hi}. If G is the direct sum of subgroups H and K then we write G = H + K, and if G is the direct sum of a set of subgroups {Hi} then we often write G = Σ Hi. Loosely speaking, a direct sum is isomorphic ...
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 ...
Classification of finite simple groups. In mathematics, the classification of finite simple groups is a result of group theory stating that every finite simple group is either cyclic, or alternating, or belongs to a broad infinite class called the groups of Lie type, or else it is one of twenty-six exceptions, called sporadic (the Tits group is ...
A 4 is the smallest group demonstrating that the converse of Lagrange's theorem is not true in general: given a finite group G and a divisor d of | G |, there does not necessarily exist a subgroup of G with order d: the group G = A 4, of order 12, has no subgroup of order 6. A subgroup of three elements (generated by a cyclic rotation of three ...