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...
@MartinSleziak I see that the tag-excerpt for regularity was recently edited (by S. Carnahan) to say that is is specifically for "regularity of solutions of PDEs".
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...
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?
