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As the title. I can't seem to find the errata to that book (4th edition) online. But I've seen somewhere people say they got it in printing form when buying the book. Does anyone know where to find it …

I'm reading Combinatorial Group Theory (by Lyndon & Schupp) and on p.2 they define a projective group $P$ to be such that, for any groups $G$, $H$ with $\gamma: G\to H$ a surjective map and $\pi: P\to …

For every group $G$, we have $$G/Z(G)\simeq \operatorname{Inn}(G).$$ I wonder whether the quotient projection has a right inverse. I suspect it doesn’t have one in general. But I can’t find a counter …

If $m<n\in\mathbb{N}$ and $(m,n)=1$, then there is a natural isomorphism $h: \mathbb{Z}_{mn}\to \mathbb{Z}_m \times \mathbb{Z}_n$. But I'm a little confused about what happens when multiplying $m$ on …

I came up with a "proof" for the Maschke's Theorem in the representation theory of finite groups that seems to make sense. But it doesn't use the fact that the group being represented is finite. So I …