Test Schwartz functions at $p$ for theta lifts of Hida families
Zheng Liu
TL;DR
The work constructs explicit $p$-adic families of theta lifts from definite orthogonal and unitary groups to symplectic/quasi-split unitary targets by carefully selecting test Schwartz functions at places above $p$ with $\,\mathbb{U}_p$-equivariance. It develops a local equivariance framework, uses the Weil representation to interpolate Fourier coefficients, and integrates $p$-adic Petersson theory with Hida theory to produce $ ext{I}$-adic, $P$-ordinary theta lifts from $H$ to $G'$ (and hence to $G$). A central achievement is the explicit specialization formula for the lifts and the construction of measure-valued theta data that interpolate the lifts across finite-order characters, culminating in an $ ext{I}$-adic $P$-ordinary family of theta lifts. The results provide a concrete mechanism to vary theta-lift data in $p$-adic families, enabling new avenues for studying $p$-adic $L$-functions and Galois representations attached to higher-rank automorphic forms.
Abstract
We construct Hida families of theta lifts from definite orthogonal and unitary groups. A major ingredient of the construction is the choice of test Schwartz functions at places dividing $p$. We select a special type of Schwartz functions endowed with the equivariance property for the action of $\mathbb{U}_p$-operators.
