Application in permutations group

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SUMMARY

The discussion centers on the application of automorphisms in permutation groups, specifically regarding the finite group G and its automorphisms a1 and a2. The key conclusion is that the function fg: G→G, defined as fg(x) = a1(g)*x*a2(g^-1), is a bijection and thus belongs to the symmetric group Sg, which is the group of all bijections on G. The condition that fg = id(G) implies g = e further establishes that this function forms a group monomorphism from G into Sym(G), preserving the group operation.

PREREQUISITES
  • Understanding of finite groups and their properties
  • Familiarity with automorphisms and their notation
  • Knowledge of symmetric groups, specifically Sym(G)
  • Basic concepts of group homomorphisms and monomorphisms
NEXT STEPS
  • Study the properties of automorphisms in group theory
  • Learn about the structure and applications of symmetric groups
  • Explore group homomorphisms and their significance in algebra
  • Investigate examples of finite groups and their automorphism groups
USEFUL FOR

Students studying abstract algebra, particularly those focusing on group theory, as well as educators seeking to clarify the concepts of automorphisms and symmetric groups.

Dassinia
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Hello
I am studying for my exam and there's a question that i don't know how to solve, I have some difficulties with symmetric/permutations groups

1. Homework Statement

Consider a finite group of order > 2.
We write Aut(G) for the group of automorphisms of G and Sg for the permutations group of the set G.
Consider a1 and a2 ∈ Aut(G) two automorphisms.
We suppose that the g=1 is the only element g ∈ G such as ∀ x ∈ G we have a1(g)*x=x*a2(g)
For g,x ∈ G we have
fg(x):=a1(g)*x*a2(g-1)
Show that for each g ∈ G the application fg: G→G is in Sg

Homework Equations

The Attempt at a Solution


I really don't know how to do that..
 
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I don't get the problem here. Since all f_g are well-defined functions on the finite set G with an obvious inverse
h_g (x) := a1(g^-1)*x*a2(g) = f_g^-1 (x), i.e. a bijection, they have to be in Sg, if Sg is Sym(G) the set of all bijections on G.

The additional condition says that f_g = id(G) implies g = e. It is also true that f_g * f_h = f_ (g*h).
Therefore you have a group monomorphism f: G → Sym(G) with f(g) := f_g, i.e. an embedding of G into Sym(G) that respects the group operation.
 
Last edited:

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