Petersson norms of not necessarily cuspidal Jacobi modular forms and applications

We extend the usual notion of Petersson inner product on the space of cuspidal Jacobi forms to include non-cuspidal forms as well. This is done by examining carefully the relation between certain “growth-killing” invariant differential operators on ${\mathbf{H}}_2$ and those on $$\mathbf{H}$_1 \times $\mathbf{C}$$(here$\mathbf H_n$denotestheSiegelupperhalfspaceofdegree$n$). As applications, we can understand better the growth of Petersson norms of Fourier Jacobi coefficients of Klingen Eisenstein series, which in turn has applications to finer issues about representation numbers of quadratic forms, and as a by-product we also show that $\mathit{\text{any}}$ Siegel modular form of degree $2$ is determined by its `fundamental’ Fourier coefficients.