Homepage Solution manuals David S. Dummit Abstract Algebra Exercise 4.5.22(If $|G| = 132$ then $G$ is not simple)

Exercise 4.5.22(If $|G| = 132$ then $G$ is not simple)

Prove that if | G | = 132 then G is not simple.

Answers

Proof. Here | G | = 132 = 2 2 3 11 . By Sylow’s Theorem

n 11 2 2 3 = 12 , n 11 1 ( 𝑚𝑜𝑑 11 ) , n 3 2 2 11 = 44 , n 3 1 ( 𝑚𝑜𝑑 3 ) .

Therefore

n 11 { 1 , 12 } , n 3 { 1 , 4 , 22 } .

Assume for the sake of contradiction that G is simple. Then n 11 1 and n 3 1 , so n 11 = 12 and n 3 = 4 or n 3 = 22 . But n 3 = 22 is impossible, otherwise G contains n 11 10 = 120 elements of order 11 , and n 3 2 = 44 elements of order 3 , which gives | G | 120 + 44 = 164 . So

n 11 = 12 , n 3 = 4 .

This gives 120 elements of order 11 and 4 2 = 8 elements of order 3 . It remains a set S of 4 elements, whose orders are neither 11 nor 3 .

Let P be any Sylow 2 -subgroup. The order of the elements of P are 1 , 2 or 4 , so P S . Since | P | = | S | = 4 , we obtain P = S , so there is a unique 2 -Sylow of G , which is normal in G , so G is not simple. This is a contradiction, which proves that G is not simple.

If | G | = 132 then G is not simple. □

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2026-03-16 11:17
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