Can You Identify 10 Non-Isomorphic Groups with Orders 25-29?

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Discussion Overview

The discussion revolves around identifying ten non-isomorphic groups with orders between 25 and 29. Participants explore the characteristics of groups of these orders, including their classification and the methods for demonstrating non-isomorphism.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Herbert questions whether it is possible to find ten groups from different isomorphism classes with orders between 25 and 29, and asks for methods to generate such a list.
  • One participant suggests that there is one group of order 25 (cyclic), two groups of order 26 (cyclic and dihedral), three abelian groups of order 27, two abelian and one dihedral group of order 28, and one group of order 29, totaling ten groups.
  • Another participant challenges the assertion that there is only one group of order 25, referencing the existence of two non-isomorphic groups of order 4 as a counterexample.
  • A later reply identifies another group of order 25, specifically C5 x C5, indicating that there are indeed multiple groups of this order.
  • One participant acknowledges a misunderstanding regarding the classification of groups of order 25, confirming that groups of this order are abelian due to their order being a prime squared.

Areas of Agreement / Disagreement

There is no consensus on the classification of groups of order 25, as participants express differing views on the number of non-isomorphic groups. The discussion remains unresolved regarding the complete list of non-isomorphic groups within the specified orders.

Contextual Notes

Participants rely on specific properties of group orders and classifications, but there are unresolved assumptions about the completeness of their lists and the definitions of isomorphism in this context.

herbert_454
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Dear All,

Is it true that one can find some 10 groups (from different isomorphism classes) with order between (and including) 25 and 29 such that each pair of the same order are not isomorphic to each other? If so, how does one go about generating such a list and showing they are not isomorphic to one another?


Herbert
 
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This should be easy to google.

Thinking out loud.. There's only one of order 25=5^2 (cyclic). Only two of order 26=2*13 (cyclic and dihedral). There are 3 abelian groups of order 27, 2 abelians and a dihedral of order 28 and only one group of order 29. So that's 10 groups right there. Any remaining groups will have to have order 27 or 28. I'll let you figure out if there are any more left.
 
Morphism, why would there be only the cyclic group of order 25? It's not just because the order is a prime squared because there are two non-isomorphic groups of order 4= 22, the cyclic group and the Klein four group.
 
Thanks! I got it. Yes there is another order 25 group, namely C5 x C5 :)
 
Oops..! What I should have said was that a group of order 25 is abelian - because its order is prime squared. I took it one step too far! Thanks for spotting that Halls.
 

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