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A sporadic group is one of the 26 exceptional groups found in the classification of finite simple groups. All the other finite simple groups form 18 infinite families numbered by q - power of prime number and n - natural number. Sporadic groups attach attention due to their sporadic/exceptional nature - similar to exceptional Lie groups. The first sporadic groups were found by Mathieu in 1860s. The last sporadic group J4 was discovered in 1975 by Janko.

4 votes
0 answers
241 views

Normalizers of abelian Sylows in simple groups

Suppose $G$ is a (nonabelian) finite simple group and $p$ is a prime such that the $p$-Sylow in $G$ is abelian. What can be said about its normalizer? I'm particularly interested in lower bounds on th …
Theo Johnson-Freyd's user avatar
3 votes
0 answers
126 views

Are all exceptional Schur covers sub-sporadic?

Famously, all but finitely many finite simple groups are (cyclic or alternating or) of Lie type. The groups of Lie type have central extensions coming from the simply connected covers of the correspon …
Theo Johnson-Freyd's user avatar
6 votes
1 answer
286 views

Which finite simple groups are rational-relative-real?

A finite group $G$ is called rational if every element $g \in G$ is conjugate to all of its primitive powers $g^a, a \in (\mathbb{Z}/\operatorname{order}(g))^\times$. Analogously, I'll call $G$ real i …
Theo Johnson-Freyd's user avatar