Mikko Korhonen
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15,292
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 91 Prove that $\sqrt 2 + \sqrt 3$ is irrational 34 Can we uniquely determine a group given the orders of its elements? 25 How to show that the commutator subgroup is a normal subgroup 21 More than 99% of groups of order less than 2000 are of order 1024? 20 Is there an idempotent element in a finite semigroup?

### Reputation (15,292)

 +5 Noncommutative rings, finding $a$ and $b$ such that every term in the sum $(a+b)^n = a^n + a^{n-1}b + \ldots$ is distinct +5 If $(|G|, |H|) > 1$, does it follow that $\operatorname{Aut}(G \times H) \neq \operatorname{Aut}(G) \times \operatorname{Aut}(H)$? +10 Number of Homomorphisms from $\Bbb{Z}_m$ to $\Bbb{Z}_n$ +10 Square of order of a Sylow p-subgroup in the nonabelian simple groups

### Questions (21)

 42 Does every Abelian group admit a ring structure? 22 When does every group with order divisible by $n$ have a subgroup of order $n$? 21 Lower bounds on the number of elements in Sylow subgroups 17 Upper bounds on the size of $\operatorname{Aut}(G)$ 15 Why does calculating matrix inverses, roots, etc. using the spectrum of a matrix work?

### Tags (92)

 875 group-theory × 223 110 rationality-testing × 2 548 abstract-algebra × 145 53 p-groups × 9 439 finite-groups × 107 34 complex-numbers × 2 140 elementary-number-theory × 13 30 alternative-proof × 4 110 radicals × 2 29 solvable-groups × 5

### Accounts (6)

 Mathematics 15,292 rep 13076 Stack Overflow 101 rep 1 Mathematics Educators 101 rep 2 MathOverflow 101 rep 12 French Language 101 rep 1