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1.
In this paper we establish the following estimate:
$$\omega \left( {\left\{ {x \in {\mathbb{R}^n}:\left| {\left[ {b,T} \right]f\left( x \right)} \right| > \lambda } \right\}} \right) \leqslant \frac{{{c_T}}}{{{\varepsilon ^2}}}\int_{{\mathbb{R}^n}} {\Phi \left( {{{\left\| b \right\|}_{BMO}}\frac{{\left| {f\left( x \right)} \right|}}{\lambda }} \right){M_{L{{\left( {\log L} \right)}^{1 + \varepsilon }}}}} \omega \left( x \right)dx$$
where ω ≥ 0, 0 < ε < 1 and Φ(t) = t(1 + log+(t)). This inequality relies upon the following sharp L p estimate:
$${\left\| {\left[ {b,T} \right]f} \right\|_{{L^p}\left( \omega \right)}} \leqslant {c_T}{\left( {p'} \right)^2}{p^2}{\left( {\frac{{p - 1}}{\delta }} \right)^{\frac{1}{{p'}}}}{\left\| b \right\|_{BMO}}{\left\| f \right\|_{{L^p}\left( {{M_{L{{\left( {{{\log }_L}} \right)}^{2p - 1 + {\delta ^\omega }}}}}} \right)}}$$
where 1 < p < ∞, ω ≥ 0 and 0 < δ < 1. As a consequence we recover the following estimate essentially contained in [18]:
$$\omega \left( {\left\{ {x \in {\mathbb{R}^n}:\left| {\left[ {b,T} \right]f\left( x \right)} \right| > \lambda } \right\}} \right) \leqslant {c_T}{\left[ \omega \right]_{{A_\infty }}}{\left( {1 + {{\log }^ + }{{\left[ \omega \right]}_{{A_\infty }}}} \right)^2}\int_{{\mathbb{R}^n}} {\Phi \left( {{{\left\| b \right\|}_{BMO}}\frac{{\left| {f\left( x \right)} \right|}}{\lambda }} \right)M} \omega \left( x \right)dx.$$
We also obtain the analogue estimates for symbol-multilinear commutators for a wider class of symbols.
  相似文献   

2.
Let
be the Fejér kernel, C be the space of contiuous 2π-periodic functions f with the norm , let
be the Jackson polynomials of the function f, and let
be the Fejér sums of f. The paper presents upper bounds for certain quantities like
which are exact in order for every function fC. Special attention is paid to the constants occurring in the inequalities obtained. Bibliography: 14 titles. Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 357, 2008, pp. 90–114.  相似文献   

3.
Remarks on the Extremal Functions for the Moser-Trudinger Inequality   总被引:1,自引:0,他引:1  
We will show in this paper that if A is very close to 1, then I(M,λ,m) =supu∈H0^1,n(m),∫m|△↓u|^ndV=1∫Ω(e^αn|u|^n/(n-1)-λm∑k=1|αnun/(n-1)|k/k!)dV can be attained, where M is a compact-manifold with boundary. This result gives a counter-example to the conjecture of de Figueiredo and Ruf in their paper titled "On an inequality by Trudinger and Moser and related elliptic equations" (Comm. Pure. Appl. Math., 55, 135-152, 2002).  相似文献   

4.
Let Θ be a bounded open set in ℝ n , n ⩾ 2. In a well-known paper Indiana Univ. Math. J., 20, 1077–1092 (1971) Moser found the smallest value of K such that
$ \sup \left\{ {\int_\Omega {\exp \left( {\left( {\frac{{\left| {f(x)} \right|}} {K}} \right)^{{n \mathord{\left/ {\vphantom {n {(n - 1)}}} \right. \kern-\nulldelimiterspace} {(n - 1)}}} } \right):f \in W_0^{1,n} (\Omega ),\left\| {\nabla f} \right\|_{L^n } \leqslant 1} } \right\} < \infty $ \sup \left\{ {\int_\Omega {\exp \left( {\left( {\frac{{\left| {f(x)} \right|}} {K}} \right)^{{n \mathord{\left/ {\vphantom {n {(n - 1)}}} \right. \kern-\nulldelimiterspace} {(n - 1)}}} } \right):f \in W_0^{1,n} (\Omega ),\left\| {\nabla f} \right\|_{L^n } \leqslant 1} } \right\} < \infty   相似文献   

5.
  A theorem from the classical complex analysis proved by Davydov in 1949 is extended to the theory of solution of a special case of the Beltrami equation in the z-complex plane (i.e., null solutions of the differential operator ). It is proved that if γ is a rectifiable Jordan closed curve and f is a continuous complex-valued function on γ such that the integral
converges uniformly on γ as r → 0, where n(ζ) is the unit vector of outer normal on γ at a point ζ and ds is the differential of arc length, then the β-Cauchy-type integral
admits a continuous extension to γ and a version of the Sokhotski–Plemelj formulas holds. Published in Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, No. 11, pp. 1443–1448, November, 2008.  相似文献   

6.
A Littlewood-Paley type inequality   总被引:2,自引:0,他引:2  
In this note we prove the following theorem: Let u be a harmonic function in the unit ball and . Then there is a constant C = C(p, n) such that
.  相似文献   

7.
Let→b=(b1,b2,…,bm),bi∈∧βi(Rn),1≤I≤m,βi>0,m∑I=1βi=β,0<β<1,μΩ→b(f)(x)=(∫∞0|F→b,t(f)(x)|2dt/t3)1/2,F→b,t(f)(x)=∫|x-y|≤t Ω(x,x-y)/|x-y|n-1 mΠi=1[bi(x)-bi(y)dy.We consider the boundedness of μΩ,→b on Hardy type space Hp→b(Rn).  相似文献   

8.
Estimates for deviations are established for a large class of linear methods of approximation of periodic functions by linear combinations of moduli of continuity of different orders. These estimates are sharp in the sense of constants in the uniform and integral metrics. In particular, the following assertion concerning approximation by splines is proved: Suppose that is odd, . Then
moreover, for it is impossible to decrease the constants on . Here, are some explicitly constructed constants, is the modulus of continuity of order r for the function f, and are explicitly constructed linear operators with the values in the space of periodic splines of degree of minimal defect with 2n equidistant interpolation points. This assertion implies the sharp Jackson-type inequality
. Bibliography: 17 titles.  相似文献   

9.
We consider the Cauchy problem for the nonlinear dissipative evolution system with ellipticity on one dimensional space
with S. Q. Tang and H. Zhao [4] have considered the problem and obtained the optimal decay property for suitably small data. In this paper we derive the asymptotic profile using the Gauss kernel G(t, x), which shows the precise behavior of solution as time tends to infinity. In fact, we will show that the asymptotic formula
holds, where D0, β0 are determined by the data. It is the key point to reformulate the system to the nonlinear parabolic one by suitable changing variables. (Received: January 8, 2005)  相似文献   

10.
In this paper the invariance criterion is applied for the nonlinear equation
(0.1)
where g(u) is a smooth function on u. Some particular set of Lie generators are given. In the case of inviscid Burger’s equation [1]
(0.2)
the Lie projectable symmetry algebra is determined, and the inviscid Burger’s equation will be connected to some order differential equations. The obtained differential equations are solved and some exact solutions of (2) are found. E.H. El Kinani, Junior Associate at The Abdus Salam ICTP, Trieste, Italy.  相似文献   

11.
We present integral versions of some recently proved results which improve the Jensen-Steffensen and related inequalities for superquadratic functions. For superquadratic functions which are not convex we get inequalities analogous to the integral Jensen-Steffensen inequality for convex functions. Therefore, we get refinements of all the results which use only the convexity of these functions. One of the inequalities that we obtain for a superquadratic function φ is
$ \bar y \geqslant \phi \left( {\bar x} \right) + \frac{1} {{\lambda \left( \beta \right) - \lambda \left( \alpha \right)}}\int_\alpha ^\beta {\phi \left( {\left| {f\left( t \right) - \bar x} \right|} \right)d\lambda \left( t \right)} $ \bar y \geqslant \phi \left( {\bar x} \right) + \frac{1} {{\lambda \left( \beta \right) - \lambda \left( \alpha \right)}}\int_\alpha ^\beta {\phi \left( {\left| {f\left( t \right) - \bar x} \right|} \right)d\lambda \left( t \right)}   相似文献   

12.
We establish conditions for the existence and uniqueness of a generalized solution of the Cauchy problem for the equation
in a Tikhonov-type class. Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, No. 5, pp. 586–602, May, 2008.  相似文献   

13.
In the present paper, the following Dirichlet problem and Neumann problem involving the p-Laplacian
((1.λ))
and
((2.λ))
are studied and some new multiplicity results of solutions for systems (1.λ) and (2.λ) are obtained. Moreover, by using the KKM principle we give also two new existence results of solutions for systems (1.1) and (2.1). This Work is supported in part by the National Natural Science Foundation of China (10561011).  相似文献   

14.
Let C be the space of continuous 2π-periodic functions f with the norm . Let , where , be the Jackson polynomials of a function f, E n (f) be the best approximation of f in the space C by trigonometric polynomials of order n, and let , be the function trigonometrically conjugate to the primitive of f. The paper establishes results of the following types:
where the symbol ≈ is independent of f and n. Bibliography: 7 titles. Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 357, 2008, pp. 115–142.  相似文献   

15.
We present a method for the solution of the Cauchy problem for three broad classes of nonlinear parabolic equations
and
with the infinite-dimensional Laplacian ΔL.  相似文献   

16.
Let U(λ, μ) denote the class of all normalized analytic functions f in the unit disk |z| < 1 satisfying the condition
$ \frac{{f(z)}} {z} \ne 0and\left| {f'(z)\left( {\frac{z} {{f(z)}}} \right)^{\mu + 1} - 1} \right| < \lambda ,\left| z \right| < 1. $ \frac{{f(z)}} {z} \ne 0and\left| {f'(z)\left( {\frac{z} {{f(z)}}} \right)^{\mu + 1} - 1} \right| < \lambda ,\left| z \right| < 1.   相似文献   

17.
We study the rough bilinear fractional integral
$ \tilde B_{\Omega ,\alpha } (f,g)(x) = \int_{\mathbb{R}^n } {f(x + y)g(x - y)\frac{{\Omega (x,y')}} {{\left| y \right|^{n - \alpha } }}dy} , $ \tilde B_{\Omega ,\alpha } (f,g)(x) = \int_{\mathbb{R}^n } {f(x + y)g(x - y)\frac{{\Omega (x,y')}} {{\left| y \right|^{n - \alpha } }}dy} ,   相似文献   

18.
Let and . We are interested in the lower bounds of the integral:
where h > 0 and . Using the lower bounds for these integrals we obtain in particular for the so-called Fejér operator of the following asymptotic expression
which essentially improves the results concerning the approximation behavior of this operator. Received: 10 January 2006  相似文献   

19.
A general algorithm is proposed for constructing interlineation operators , x=(x1, x2) with the properties
  相似文献   

20.
In this paper we consider the weakly coupled elliptic system with critical growth
where a, b, c, d are C 1-functions defined in a bounded regular domain of N . Here we construct families of solutions which blow-up and concentrate at some points in as the positive parameter goes to zero.*The authors are supported by M.I.U.R., project Metodi variazionali e topologici nello studio di fenomeni non lineari.  相似文献   

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