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・ Holospira oritis
・ Holospira pasonis
・ Holospira pityis
・ Hololena curta
・ Hololepis
・ Hololepta aequalis
・ Hololepta plana
・ Hololoma
・ Holoman-Outland House
・ Holomatix Rendition
・ Holomek
・ Holometabolism
・ Holometer
・ Holomictic lake
・ Holomorph
Holomorph (mathematics)
・ Holomorphic curve
・ Holomorphic discrete series representation
・ Holomorphic embedding load flow method
・ Holomorphic function
・ Holomorphic functional calculus
・ Holomorphic Lefschetz fixed-point formula
・ Holomorphic sheaf
・ Holomorphic tangent space
・ Holomorphic vector bundle
・ Holomorphically convex hull
・ Holomorphically separable
・ Holomovement
・ Holomycota
・ Holon


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Holomorph (mathematics) : ウィキペディア英語版
Holomorph (mathematics)
In mathematics, especially in the area of algebra known as group theory, the holomorph of a group is a group which simultaneously contains (copies of) the group and its automorphism group. The holomorph provides interesting examples of groups, and allows one to treat group elements and group automorphisms in a uniform context. In group theory, for a group G, the holomorph of G denoted \operatorname(G) can be described as a semidirect product or as a permutation group.
==Hol(''G'') as a semi-direct product==
If \operatorname(G) is the automorphism group of G then
:\operatorname(G)=G\rtimes \operatorname(G)
where the multiplication is given by
:(g,\alpha)(h,\beta)=(g\alpha(h),\alpha\beta). (1 )
Typically, a semidirect product is given in the form G\rtimes_A where G and A are groups and \phi:A\rightarrow \operatorname(G) is a homomorphism and where the multiplication of elements in the semi-direct product is given as
:(g,a)(h,b)=(g\phi(a)(h),ab)
which is well defined, since \phi(a)\in \operatorname(G) and therefore \phi(a)(h)\in G.
For the holomorph, A=\operatorname(G) and \phi is the identity map, as such we suppress writing \phi explicitly in the multiplication given in (1 ) above.
For example,
* G=C_3=\langle x\rangle=\ the cyclic group of order 3
* \operatorname(G)=\langle \sigma\rangle=\ where \sigma(x)=x^2
* \operatorname(G)=\ with the multiplication given by:
:(x^,\sigma^)(x^,\sigma^) = (x^,\sigma^) where the exponents of x are taken mod 3 and those of \sigma mod 2.
Observe, for example
:(x,\sigma)(x^2,\sigma)=(x^,\sigma^2)=(x^2,1)
and note also that this group is not abelian, as (x^2,\sigma)(x,\sigma)=(x,1), so that \operatorname(C_3) is a non-abelian group of order 6 which, by basic group theory, must be isomorphic to the symmetric group S_3.

抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
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