6:57 AM
The question Index of the congruence subgroups of $PGL_2(\mathbb{Z}_p)$ has the deprecated tag (abstract-algebra). Should it be simply removed, or should it be replaced by some other tag?
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Let $\Gamma_n$ be the $n$-th congruence subgroup of $GL(2,\mathbb{Z}_p)$. So $\Gamma_n$ consists of matrices in $GL(2,\mathbb{Z}_p)$ which are congruent to the identity matrix modulo $p^n$. Let $Z(\Gamma_n)$ the the center of $\Gamma_n$. My question is to compute the index $[\Gamma_n/Z(\Gamma_n... 6 hours later… 12:30 PM @MartinSleziak I see that the tag-excerpt for was recently edited (by S. Carnahan) to say that is is specifically for "regularity of solutions of PDEs". 3 hours later… 4:00 PM 0 Is there a model of${\sf (ZFC)}$such that in the model we have that$\kappa$is a limit cardinal if and only if$2^\kappa\$ is a limit cardinal?