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Corollary to Cayley's Theorem
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Every finite group G of order n is isomorphic to a subgroup of the symmetric group S_n.
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The right coset Ka denotes:
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Ka = {ka| k in K}, where a is a fixed element of the group.
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Lagrange's Theorem
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If G is a finite group and K is a subgroup of G, then
|G| = |K| |[G:K]|.
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Def: The index of a subgroup K in a group G
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Is the number of distinct right cosets of K in G.
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Let p be a prime integer. Then every group of order p is...
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Cyclic, and therefore isomorphic to Z_p.
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If N is a normal subgroup of a group G, then the following are equivalent:
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1) Na = aN for every a in G.
2) (a^-1)Na is a subset of N for every a in G.
3) (a^-1)Na is equal to N for every a in G. |
G/N denotes...
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...The set of all right cosets of N in G.
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G/N is a group under the operation (Na)(Nb) = N(ab) if...
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...N is a normal subgroup of G.
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If G is finite and N is a normal subgroup of G, then the order of G/N is ...
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...|G|/|N|.
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If G is abelian and N is a normal subgroup of G, then G/N is...
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...Abelian!
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Let N be a normal subgroup of G. Then G/N is abelian if and only if...
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...ab(a^-1)(b^-1) is in N for every a, b in G.
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If G is a group such that the quotient group G/Z(G) is cyclic, then...
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...G is abelian.
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Let f: G->H be a homomorphism of groups with kernel K. Then...
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...K is a normal subgroup of G.
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Let f: G->H be a homomorphism of groups with kernel K. Then K = <e_G> if and only if...
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...f is injective.
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First Isomorphism Theorem for Groups:
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Let f: G->H be a surjective homomorphism of groups with kernel K. Then the quotient group G/K is isomorphic to H.
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