On the Petersson norm $\langleθ_ψ,θ_ψ\rangle$

Abstract

Let $K$ be an imaginary quadratic field of discriminant~$-d<-11$, and for $\ell\geq1$, let $ψ$ be a Hecke character of $K$ with trivial finite conductor and infinite type~$(2\ell,0)$. In this work we prove that for any prime $p>3$, the quotient $$ \frac{\langleθ_ψ,θ_ψ\rangle}{Ω_{K}^{4\ell}}, $$ is $λ$-integral for a prime ideal $λ$ over $p$, where $\langleθ_ψ,θ_ψ\rangle$ is the Petersson norm of the theta function $θ_ψ=θ_ψ(τ)$ attached to $ψ$, and $Ω_{K}$ denotes the Chowla--Selberg period attached to~$K$, and the product $$ \prod_{i=1}^{h_{K}}\frac{\langleθ_{ψ_{i}},θ_{ψ_{i}}\rangle}{Ω_{K}^{4\ell}} $$ is rational, where the product is over all $h_{K}$ of the underlying Hecke characters.