Abstract. We prove a T (1) Theorem to completely characterize compactness of Calderón-Zygmund operators. The result provides sufficient and necessary conditions for the compactness of singular integral operators acting on L p (R) with 1 < p < ∞.

Abstract. We prove a T(1) theorem for bilinear singular integral operators (trilinear forms) with a one-dimensional modulation symmetry.

We give almost sharp conditions under which the maximal operator associated with the wave equation with initial data in Sobolev space H^s(R^n) is bounded from H^s(R^n) to L^q(R^n).Comment: 7 pages, 1 figur

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We prove a new T(1) theorem for multiparameter singular integral operators.