Valentin Blomer (Toronto)

Bounding sup-norms of cusp forms

Given an L²-normalized cusp form f on a modular curve X₀(N), what can be said about pointwise bounds for f? For Hecke eigenforms, we will prove the first non-trivial bound in terms of the level N as well as hybrid bounds in terms of the level and the Laplacian eigenvalue. Similar techniques work for functions on other spaces, e.g. quotients of quaternion algebras. This is joint work with R. Holowinsky.