Paper detail

The Boundedness of the (Sub)Bilinear Maximal Function along "non-flat" smooth curves

Let $\mathcal{N}\mathcal{F}$ be the class of smooth non-flat curves near the origin and near infinity previously introduced by the second author and let $γ\in\mathcal{N}\mathcal{F}$. We show - via a unifying approach relative to the correspondent bilinear Hilbert transform $H_Γ$ - that the (sub)bilinear maximal function along curves $Γ=(t,-γ(t))$ defined as $$M_Γ(f,g)(x):=\sup\limits_{ε>0} \frac{1}{2ε} \int_{-ε}^ε |f(x-t)\,g(x+γ(t))|\,dt$$ is bounded from $L^p(\mathbb{R})\times L^{q}(\mathbb{R})\to L^r(\mathbb{R})$ for all $p, q$ and $r$ Hölder indices, that is $\frac{1}{p}+\frac{1}{q}=\frac{1}{r}$, with $1<p,\,q\leq\infty$ and $1\le r\leq\infty$. This is the maximal boundedness range for $M_Γ$, that is, our result is sharp.