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C_\infty
• 無限二面體群D_\infty
• 無限單群

參考

• McCarthy, D., [http://onlinelibrary.wiley.com/doi/10.1002/cpa.3160210604/pdf Infinite groups whose proper quotient groups are finite, I] . Communications on Pure and Applied Mathematics. 1968, 21(6):545–562.
• McCarthy, D., [http://onlinelibrary.wiley.com/doi/10.1002/cpa.3160230506/pdf Infinite groups whose proper quotient groups are finite, II] . Communications on Pure and Applied Mathematics. 1970, 23(5):767–789.