Boundedness of bilinear radial Fourier multipliers

Abstract

We show that a bilinear radial Fourier multiplier operator with symbol $σ$ is $L^2(\R^n)\times L^2(\R^n) \to L^1(\R^n)$ bounded, $n\in \mathbb N,$ if the function $σ$ satisfies the smoothness condition $σ(2^j\cdot)Φ\in L^2_{1/2 +ε}(\mathbb R^{2n})$ for some $ε>0$ and every $j\in \mathbb Z,$ where $Φ$ is a smooth cutoff function adapted to the annulus $|x|\in [1/4,4]$. This condition is dimension free. We also apply similar reasoning to provide alternative proof of the initial result concerning multilinear Bochner-Riesz operator and prove an estimate for generalized bilinear Bochner-Riesz operator.