Math 2.0

Group theory and generalizations Proposition

Abelian simple groups have prime order

Builds on Simple groupCyclic groupCauchy's theoremSubgroups of cyclic groups are cyclic

Statement

Let GG be an abelian group. Then GG is simple if and only if GG is finite of prime order. In that case, GG is cyclic, and G≅ℤ/pℤG \cong \mathbb{Z}/p\mathbb{Z} for a prime number pp.

Remarks

In an abelian group, each subgroup is normal, so a simple abelian group has no subgroup except {e}\{e\} and itself. Then G=⟨g⟩G = \langle g \rangle for each g≠eg \neq e, so GG is cyclic; ℤ\mathbb{Z} is not simple, because 2ℤ2\mathbb{Z} is a proper nontrivial subgroup. A finite cyclic group of order nn has a subgroup of order dd for each divisor dd of nn, so nn must be prime.

Reading path

To understand this page from the ground up, read these 65 pages in order. The foundations come first. The path takes the proof Proof of Lagrange's theorem.

  1. Element definition
  2. Group concept
  3. Left coset concept
  4. Proposition concept
  5. Set definition
  6. Conjugate elements definition
  7. Group homomorphism definition
  8. Laws of exponents in a group statement
  9. Order of a group definition
  10. Subgroup definition
  11. Symmetric group definition
  12. Conjunction definition
  13. Disjunction definition
  14. Implication definition
  15. Predicate definition
  16. Empty set object
  17. Family of sets definition
  18. Ordered pair definition
  19. Order of an element definition
  20. Intersection definition
  21. Union definition
  22. Conjugate subgroup definition
  23. Group action definition
  24. Cyclic subgroup generated by an element definition
  25. Left coset definition
  26. Right coset definition
  27. Set-builder notation concept
  28. Subgroup criterion statement
  29. Existential quantifier definition
  30. Universal quantifier definition
  31. Cartesian product definition
  32. Disjoint sets definition
  33. P-group definition
  34. Normal subgroup definition
  35. Subset definition
  36. Stabiliser definition
  37. Union of a family of sets definition
  38. Orbit definition
  39. Cyclic group definition
  40. Intersection of subgroups is a subgroup statement
  41. Index of a subgroup definition
  42. Cosets have the same cardinality as the subgroup statement
  43. Binary relation definition
  44. Simple group definition
  45. Partition of a set definition
  46. Normal core definition
  47. Fixed points of an action definition
  48. Subgroups of cyclic groups are cyclic statement
  49. Orbits partition the set statement
  50. Transitive action definition
  51. Order of a group is the index times the order of the subgroup statement
  52. Reflexive relation definition
  53. Symmetric relation definition
  54. Transitive relation definition
  55. Action on left cosets example
  56. Equivalence relation definition
  57. Orbit-stabiliser theorem statement
  58. Equivalence class definition
  59. Equivalence classes form a partition statement
  60. Proof of Lagrange's theorem proof
  61. Lagrange's theorem statement
  62. Size of an orbit times the size of the stabiliser statement
  63. Fixed points of a p-group action statement
  64. Cauchy's theorem statement
  65. Abelian simple groups have prime order statement

Further reading

  1. Web https://en.wikipedia.org/wiki/Simple_group, Examples
  2. Web https://en.wikipedia.org/wiki/Simple_group, Finite simple groups
About this page
Tag0JJV80RXHD
URIm2://0JJV80RXHD
Kindstatement, proposition
WritingW0 stub
MSC20E32, 20K01
StatusThis copy of the site has no build data. Run m2 status 0JJV80RXHD.
UsesSimple group, Cyclic group, Cauchy's theorem, Subgroups of cyclic groups are cyclic

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