Motivating goal: Subconvexity for twists \(F\) is a number field. \(\pi:\mathrm{GL}_n\), \(\chi:\mathrm{GL}_1\) \[\begin{align} \label{subconvex-twists} L(\pi\times\chi,&1/2)\ll_\pi C(\chi)^{n/4-\delta}\tag{$\star$} \\ &\Bigg\updownarrow \substack{\text{(Lapid-Mao) $n$ is even, $\pi$ comes from $\mathrm{SO}(n+1)$},\\ \text{$\chi$ quadratic, $C_\mathrm{fin}(\chi)\approx\square$-free}}\notag\\ \text{Fourier} & \text{ coefficients on $Mp_n$}\notag \end{align}\]