Top network posts

• 23 morphisms representable by algebraic spaces vs morphisms representable by schemes
• 23 For which $n$ is it true that all surjections $SL_2(\mathbb{Z})\rightarrow SL_2(\mathbb{Z}/n\mathbb{Z})$ have kernel $\Gamma(n)$?
• 22 Is $\widehat{\mathbb{Z}}[[t]]\cong\widehat{\mathbb{Z}}[[\widehat{\mathbb{Z}}]]$?
• 15 Is every normal subgroup of $SL_2(\mathbb{Z}/n)$ also normal inside $GL_2(\mathbb{Z}/n)$?
• 14 When is the inverse image of the structure sheaf the structure sheaf?
• 12 are the congruence subgroups $\Gamma(n)$ characteristic inside $\mathrm{SL}_2(\mathbb{Z})$?
• 12 Difference between the completed group algebra and the profinite completion of a group ring
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