Joint cubic moment of Eisenstein series and Hecke-Maass cusp forms (2410.04448v2)

Abstract: Let $F(z), G(z)$ be Hecke-Maass cusp forms or Eisenstein series and $\psi$ is a smooth compactly supported function on X = SL(2,Z)\H. In this paper, we are interested in the asymptotic behavior of joint moment like $\int_{X}\psi(z) F(z)^{a_1}G(z)^{a_2}d\mu z $ when the spectral parameters go to infinity with nonnegative integers $a_{1}+a_{2} = 3$. We show that the diagonal case $\int_{X}\psi(z)E_{t}(z)^{3} d\mu z = O_{\psi}(t^{-1/3+\varepsilon})$. In nondiagonal case we show $\int_{\mathbb{X}}\psi(z)f^{2}(z)g(z)d\mu z = o(1)$ in the range $|t_{f} - t_{g}| \leq t_{f}^{2/3-\omega}$, a power saving upper bound of $\frac{1}{2\log t}\int_{X}\psi(z)|E_{t}(z)|^{2}g(z)d\mu z$ in the range $t_{g} \geq 2t^{\varepsilon^{\prime}}$ for any $\varepsilon^{\prime} >0 $ and an explicit formula when $t_{g} \leq 2t^{\varepsilon^{\prime}}$ which will asymptotically vanish under GRH and GRC.