MHB Lower Central Series: Meaning of Gamma of G

[Pratibha]

In definition of lower central series we use the notation called ,gamma of G, what is meaning of this gamma of G ? please help...

 

[Fallen Angel]

Hi,

Do you refer the notation in wiki?
Central series - Wikipedia, the free encyclopedia

There, $\gamma_{n}(G)=G_{n}$ it's just a description notation, I mean, this is like when you take a sequence and write $a_{n}=(whatever)$ but in this case, as the lower central series of a group is unique we can think in an "operator" family ($\gamma_{n}$) that sends every group to the $n-$th term of his lower central series ($G_{n}$).