On the bilinear square Fourier multiplier operators and related multilinear square functions

Abstract

Let n > 1 and T m be the bilinear square Fourier multiplier operator associated with a symbol m, which is defined by $${T_m}\left( {{f_1},{f_2}} \right)\left( x \right) = {\left( {\int_0^\infty {{{\left| {\int_{{{\left( {{\mathbb{R}^n}} \right)}^2}} {{e^{2\pi ix \cdot \left( {{\xi _1} + {\xi _2}} \right)}}m\left( {t{\xi _1},t{\xi _2}} \right){{\hat f}_1}\left( {{\xi _1}} \right){{\hat f}_2}\left( {{\xi _2}} \right)d{\xi _1}d{\xi _2}} } \right|}^2}\frac{{dt}}{t}} } \right)^{\frac{1}{2}}}.$$ Let s be an integer with s ∈ [n + 1, 2n] and p 0 be a number satisfying 2n/s ≤ p 0 ≤ 2. Suppose that $${\nu _{\vec \omega }} = \Pi _{i = 1}^2\omega _i^{p/{p_i}}$$ and each ω i is a nonnegative function on R n . In this paper, we show that under some condition on m, T m is bounded from L p1(ω 1) × L p2(ω 2) to $${L^p}\left( {{\nu _{\vec \omega }}} \right)$$ if p 0 < p 1, p 2 < ∞ with 1/p = 1/p 1 + 1/p 2. Moreover, if p 0 > 2n/s and p 1 = p 0 or p 2 = p 0, then T m is bounded from L p1(ω 1) × L p2(ω 2) to $${L^{p,\infty }}\left( {{\nu _{\vec \omega }}} \right)$$ . The weighted end-point L log L type estimate and strong estimate for the commutators of T m are also given. These were done by considering the boundedness of some related multilinear square functions associated with mild regularity kernels and essentially improving some basic lemmas which have been used before.