This paper is concerned with Wiener-Hopf integral operators on Lp and with Toeplitz operators (or matrices) on lp. The symbols of the operators are assumed to be continuous matrix functions. It is well known that the invertibility of the operator itself and of its associated operator imply the invertibility of all sufficiently large truncations and the uniform boundedness of the norms of their ...

Let Lε = −div ` A ` x ε ́ ∇ ́ , ε > 0 be a family of second order elliptic operators with real, symmetric coefficients on a bounded Lipschitz domain Ω in Rn, subject to the Dirichlet boundary condition. Assuming that A(x) is periodic and belongs to VMO, we show that there exists δ > 0 independent of ε such that Riesz transforms ∇(Lε)−1/2 are uniformly bounded on Lp(Ω), where 1 < p < 3+δ if n ≥ 3,...

This study focuses on anisotropic Sobolev type spaces associated with Banach spaces E0, E. Several conditions are found that ensure the continuity and compactness of embedding operators that are optimal regular in these spaces in terms of interpolations of E0 and E. In particular, the most regular class of interpolation spaces Eα between E0, E, depending of α and order of spaces are found that ...

We develop a unified approach to proving Lp−Lq boundedness of spectral projectors, the resolvent Laplace-Beltrami operator and its derivative on Hd. In case when p q are in duality, dependence implicit constant is shown be sharp. also give partial results question Fourier extension operator. As an application, we prove smoothing estimates for free Schrödinger equation Hd limiting absorption pri...

The natural BMO (bounded mean oscillation) conditions suggested by scalar-valued results are known to be insufficient for the boundedness of operator-valued paraproducts. Accordingly, singular integrals has only been available under versions classical “T(1)?BMO” assumptions that not easily checkable. Recently, Hong, Liu and Mei (J. Funct. Anal. 2020) observed situation improves remarkably with ...

We find optimal conditions on m-linear Fourier multipliers to give rise to bounded operators from a product of Hardy spaces Hj , 0 < pj ≤ 1, to Lebesgue spaces Lp. The conditions we obtain are necessary and sufficient for boundedness and are expressed in terms of L2-based Sobolev spaces. Our results extend those obtained in the linear case (m = 1) by Calderón and Torchinsky [1] and in the bilin...

Weighted Norm theory forms a basic component of the study of singular integrals. Here one attempts to characterize those measure spaces over which a broad class of singular integral operators remain bounded. For the case of singular integral operators on C-valued functions in Euclidean space, the answer is given by the Hunt-Muckenhoupt-Wheeden theorem [10]. It states that the necessary and suff...

We now consider the family of operators Tλ, λ ≥ 0, defined on Rn by T̂λ f (ξ) = mλ f̂ (ξ), where mλ(ξ) = (1− |ξ|)+. These are the Bochner-Riesz multipliers, which can be viewed as an attempt to smooth out the singularity of the disc multiplier to see if we can obtain boundedness on a wider range of Lp spaces. Note that when λ = 0 we obtain S1, and that as λ increases, the multiplier mλ becomes sm...