Automorphism Groups: Finite Cyclic G of Order n

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SUMMARY

The discussion focuses on the automorphism groups of a finite cyclic group G of order n, specifically analyzing Aut(G) and Aut(Aut(G)). It is established that Aut(G) consists of automorphisms that map a generator to a power k, where k is coprime to n, resulting in a group of order φ(n), where φ is Euler's totient function. The challenge lies in understanding Aut(Aut(G)), which is not generally cyclic, and requires further exploration of its structure and group law.

PREREQUISITES
  • Understanding of finite cyclic groups and their properties
  • Familiarity with group theory concepts, particularly automorphisms
  • Knowledge of Euler's totient function, φ(n)
  • Basic skills in visualizing group structures and isomorphisms
NEXT STEPS
  • Research the structure of automorphism groups for various types of groups
  • Study the properties of Euler's totient function, φ(n), in depth
  • Explore examples of Aut(Aut(G)) for specific finite cyclic groups
  • Learn about group laws and their implications in automorphism groups
USEFUL FOR

Students of abstract algebra, mathematicians specializing in group theory, and anyone interested in the properties of automorphism groups in finite cyclic structures.

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Homework Statement



If G is a finite cyclic group of order n, what is the group Aut(G)? Aut(Aut(G))?

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The Attempt at a Solution



Aut(G) is given by the automorphisms that send a generator to a power k < n where (k,n) = 1 with order p(n) where p is Euler's function.

I'm having trouble visualizing or describing Aut(Aut(G)) as automorphisms of automorphisms. Is Aut(G) isomorphic to a cyclic group of order p(n)?
 
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It is not going to be cyclic in general. You need to try to get a better view of Aut(G).

You've already identified it as a set as

{ k : 1<=k <n and (k,n)=1}

What is the group law?
 

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