Let MX,w(ℝ) denote the algebra of the Fourier multipliers on a separable weighted Banach function space X(ℝ,w).We prove that if the Cauchy singular integral operator S is bounded on X(ℝ, w), thenMX,w(ℝ) is continuously embedded into L∞(ℝ). An important consequence of the continuous embedding MX,w(ℝ) ⊂ L∞(ℝ) is that MX,w(ℝ) is a Banach algebra.
We give one sufficient and two necessary conditions for boundedness between Lebesgue or Lorentz spaces of several classes of bilinear multiplier operators closely connected with the bilinear Hilbert transform.
Let be a metric measure space endowed with a distance and a nonnegative Borel doubling measure . Let be a non-negative self-adjoint operator of order on . Assume that the semigroup generated by satisfies the Davies-Gaffney estimate of order and satisfies the Plancherel type estimate. Let be the Hardy space associated with We show the boundedness of Stein’s square function arising from Bochner-Riesz means associated to from Hardy spaces to , and also study the boundedness...