Just-infinite群

群論中一個無限群G稱為just-infinite，如果G的所有真商群都是有限群，也就是說所有非平凡正規子群都有有限指數。

例子
 無限循環群
 無限二面體群
 無限單群

參考
 McCarthy, D., Infinite groups whose proper quotient groups are finite, I . Communications on Pure and Applied Mathematics. 1968, 21(6):545–562.
 McCarthy, D., Infinite groups whose proper quotient groups are finite, II . Communications on Pure and Applied Mathematics. 1970, 23(5):767–789.

群論