Central Values of $GL(2)\times GL(3)$ Rankin-Selberg $L$-functions with Applications

Let $f$ be a normalized holomorphic cusp form for $SL_2(\mathbb{Z})$ of weight $k$ with $k\equiv0\bmod 4$. By the Kuznetsov trace formula for $GL_3(\mathbb R)$, we obtain the first moment of central values of $L(s,f\otimes \phi)$, where $\phi$ varies over Hecke-Maass cusp forms for $SL_3(\mathbb Z)$. As an application, we obtain a non-vanishing result for $L(1/2,f\otimes\phi)$ and show that such $f$ is determined by $\{L(1/2,f\otimes\phi)\}$ as $\phi$ varies.