Weighted and unweighted regularity of bilinear pseudo-differential operators with symbols in general H\"{o}rmander classes

TL;DR

This paper studies the boundedness and regularity of bilinear pseudo-differential operators with symbols in Hörmander classes, extending previous results to broader parameter ranges and establishing weighted inequalities.

Contribution

It generalizes boundedness and regularity results for bilinear pseudo-differential operators to the full range of Hörmander class parameters, including new weighted norm inequalities.

Findings

Established boundedness conditions for operators in the regime $0 \\leq \\varrho < \\\delta < 1$.

Developed refined pointwise estimates via sharp maximal functions.

Extended previous results to more general parameter ranges and weighted inequalities.

Abstract

This paper investigates the boundedness of bilinear pseudo-differential operators with symbols in the H\"{o}rmander class $BS_{\varrho,\delta}^m(\mathbb{R}^n)$ in the previously unexplored regime $0 \leq \varrho < \delta < 1$. We establish boundedness from $H^p(\mathbb{R}^n) \times H^q(\mathbb{R}^n)$ to $L^r(\mathbb{R}^n)$ (with $L^r$ replaced by $\mathrm{BMO}$ when $p=q=r=\infty$) under the probably optimal condition on the order $$m \leq m_\varrho(p,q) - \frac{n\max\{\delta-\varrho,0\}}{\max\{r,2\}},$$ where $m_\varrho(p,q)$ is the critical order in the case $0\leq\delta\leq\varrho<1.$ Furthermore, we develop refined pointwise estimates via sharp maximal functions, establishing that for $m \leq -n(1-\varrho)(\frac{1}{\min\{r_1,2\}}+ \frac{1}{\min\{r_2,2\}})$ with $1<r_{1},r_{2}<\infty$, the bilinear operators satisfy $$M^\sharp T_a(f_1,f_2)(x) \lesssim \mathcal{M}_{\vec{r}}(f_1,f_2)(x).$$ This extends the parameter range from the restrictive condition $0 \leq \delta \leq \varrho < 1$ to the general setting $0 \leq \varrho \leq 1$, $0 \leq \delta < 1$ with $\delta > \varrho$ permitted, and generalizes previous results of Park and Tomita to distinct exponent pairs. Consequently, we obtain weighted norm inequalities for bilinear pseudo-differential operators under multilinear $A_{\vec{p},(\vec{r},\infty)}$ weights.