The **Siegel $\Phi$ operator** is a linear map that sends degree $g$ Siegel modular forms to degree $g-1$ ones; it is defined by
\[
\Phi(f)(\tau) = \lim_{t\to +\infty}
f\begin{pmatrix}\tau&0\\0&it\end{pmatrix} \quad \text{for any } \tau \in \mathfrak{H}_{g-1}.
\]

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- Review status: beta
- Last edited by Fabien Cléry on 2024-01-11 05:57:27

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