On the slopes of the $U_5$ operator acting on overconvergent modular forms

Abstract

We show that the slopes of the~$U_5$ operator acting on slopes of 5-adic overconvergent modular forms of weight~$k$ with primitive Dirichlet character~$\chi$ of conductor~25 are given by either \[ \left\{{1/4}\cdot\lfloor\frac{8i}{5}\rfloor: i \in \N\right\}\text{or }\left\{{1/4}\cdot\lfloor\frac{8i+4}{5}\rfloor: i \in \N\right\}, \] depending on~$k$ and~$\chi$.