METRIZABILITY OF SPACES AND J.NAGATA'S PROBLEM

In 1988, J.Nagata raised a problem about metrizability. The present article is an attempt to find a solution to the problem.     

Weakly singular initial values for the Stokes equation on a half space

We study the extension of Ukai's formula to the case of singular initial values for the Stokes problem on the half space.     

A REMARK ON THE BLOW-UP CRITERION OF STRONG SOLUTIONS AND REGULARITY FOR WEAK SOLUTIONS OF NAVIER-STOKES EQUATIONS

We give blow-up criteria of strong solutions of Navier-Stokes equations with its initial data in Besov spaces and consider the regularity of Leray-Hopf solutions of the equation.     

关于分层空间度量化的一个问题

利用g-函数研究广义度量空间和度量化,统一了近年来许多有趣的工作.本文回答了[2]中提出的一个问题.所讨论的拓扑空间是正则的.     

Littlewood-Paley g_λ~*-函数交换子的Hardy型估计

研究了Littlewood-Paley g_λ~*-函数交换子的端点估计.利用函数分解技术,证明了当q1时g_λ~*-函数与LMO(R~n)(BMO(R~n)的一个子空间)函数生成的交换子[b,g_λ~*]是局部Hardy空间h1(R~n)到空间h~1(R~n)+L~q(R~n)的一个连续映射.推广了Coifman,Rochberg和Weiss关于交换子的经典结果.     

Weighted inequalities for multilinear commutators of some sublinear operators

We establish sharp estimates for some multilinear commutators related to the Littlewood-Paley and Marcinkiewicz operators. As an application, we obtain the weighted norm inequalities and L log L type estimate for the multilinear commutators.      

<Emphasis Type="Italic">H</Emphasis><Superscript>1</Superscript>-estimates of Littlewood-Paley and Lusin functions for Jacobi analysis

For α≥β≥ -1/2 let Δ(x) = (2shx)2α+1(2chx)2β+1 denote the weight function on R+ and L1(Δ) the space of integrable functions on R+ with respect to Δ(x)dx, equipped with a convolution structure. For a suitable φ∈ L1(Δ), we put φt(x) = t-1Δ(x)-1Δ(x/t)φ(x/t) for t > 0 and define the radial maximal operator Mφ as usual manner. We introduce a real Hardy space H1(Δ) as the set of all locally integrable functions f on R+ whose radial maximal function Mφ(f) belongs to L1(Δ). In this paper we obtain a relation between...     

On the Radius of Analyticity of Solutions to 3D Navier-Stokes System with Initial Data in Lp

Given initial data u₀ ∈ L^p(R³) for some p in[3, 18/5[, the auhtors ?rst prove that 3D incompressible Navier-Stokes system has a unique solution u = uL+v with uL def = et^?u0 and v ∈ e L^∞([0, T]; ˙ H^{5/2 ? 6/p} ) ∩ L¹(]0, T[; ˙H^{9/2 ? 6/p} ) for some positive time T. Then they derive an explicit lower bound for the radius of space analyticity of v, which in particular extends the corresponding results in [Chemin, J.-Y., Gallagher, I. and Zhang, P., On the radius of analyticity of solutions to semi-linear parabolic system, Math. Res. Lett., 27, 2020, 1631– 1643, Herbst, I. and Skibsted, E., Analyticity estimates for the Navier-Stokes equations, Adv. in Math., 228, 2011, 1990–2033] with initial data in ˙H^s(R³) for s∈[1/2,3/2[.     

Endpoint estimates of generalized homogeneous Littlewood–Paley <Emphasis Type="Italic">g</Emphasis>-functions over non-homogeneous metric measure spaces

Let (χ, d, μ) be a metric measure space satisfying both the geometrically doubling and the upper doubling conditions. Under the weak reverse doubling condition, the authors prove that the generalized homogeneous Littlewood-Paley g-function_r (r∈[2,∞)) is bounded from Hardy space H¹(μ) into L¹(μ). Moreover, the authors show that, if f ∈ RBMO(μ), then[_r(f)]^r is either infinite everywhere or finite almost everywhere, and in the latter case,[_r(f)]^r belongs to RBLO(μ) with the norm no more than ‖f‖_RBMO(μ) multiplied by a positive constant which is independent of f. As a corollary, the authors obtain the boundedness of_r from RBMO(μ) into RBLO(μ). The vector valued Calderón-Zygmund theory over (χ, d, μ) is also established with details in this paper.     

On the Small Ball Inequality in all dimensions

Let hR denote an L^∞ normalized Haar function adapted to a dyadic rectangle R⊂d[0,1]. We show that for choices of coefficients α(R), we have the following lower bound on the L^∞ norms of the sums of such functions, where the sum is over rectangles of a fixed volume: