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Pablo
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What is the corank of the commutatora proper char subgroup of a finite index subgroup of a free group?

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Pablo
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Let $F$ be the free group of rank $\aleph_0$, and let $L \leq F$ be a finite index subgroup. Denote by, and let $M = L' = [L,L]$ the commutator$M$ be a proper characteristic subgroup of $L$. Is it possible that there exists a finite subset $S \subseteq F$ for which we have $\langle M,S \rangle = F$  ?

Note that if $L = F$ then the answer is clearly negative.

Let $F$ be the free group of rank $\aleph_0$, and let $L \leq F$ be a finite index subgroup. Denote by $M = L' = [L,L]$ the commutator subgroup of $L$. Is it possible that there exists a finite subset $S \subseteq F$ for which $\langle M,S \rangle = F$  ?

Note that if $L = F$ then the answer is clearly negative.

Let $F$ be the free group of rank $\aleph_0$, let $L \leq F$ be a finite index subgroup, and let $M$ be a proper characteristic subgroup of $L$. Is it possible that there exists a finite subset $S \subseteq F$ for which we have $\langle M,S \rangle = F$?

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Pablo
  • 11.3k
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  • 68

What is the corank of the commutator of a finite index subgroup of a free group?

Let $F$ be the free group of rank $\aleph_0$, and let $L \leq F$ be a finite index subgroup. Denote by $M = L' = [L,L]$ the commutator subgroup of $L$. Is it possible that there exists a finite subset $S \subseteq F$ for which $\langle M,S \rangle = F$ ?

Note that if $L = F$ then the answer is clearly negative.