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Antoine
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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 Nice Question
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
Many thanks for this nice answer. Out of curiosity, do you know if this is the smallest possible G providing a counter example?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
Thank you very much, of course I meant surjective morphisms. Edited.
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Does a fibre product of a group $G$ with itself have a subgroup isomorphic to $G$?
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Lifting automorphisms on a Blow-up surface
Why is the morphism $f$ injective? I see clearly why an automorphism in $\ker(f)$ is trivial away from $E$, but why is it also the identity on $E$?