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1.
A. G. Babenko 《Mathematical Notes》1996,60(3):248-263
In this paper we prove the Jackson-Stechkin inequalityE
n−1(f)<ω
n
(f, 2τ
n
,λ),n≥1,m≥5,r≥1, f ∈L2(
),f ≢ const, which is sharp for eachn=2, 3, ...; hereE
n−1
(f) is the best approximation of a functionf by spherical polynomials of degree ≤n−1, ω
n
(f, τ) is theτth modulus of continuity off based on the translations
,t ∈ ℝ,x ∈
,
,
is the measure of the unit Euclidean sphere
,
, andτ
n
,λ is the first positive zero of the Gegenbauer cosine polynomial
(cost).
Translated fromMatematicheskie Zametki, Vol. 60, No. 3, pp. 333–355, September, 1996.
The present paper was discussed at Ural State University in a seminar headed by Professor Arestov. The author is grateful
to Professor Arestov and Associate Professor Popov for useful conversations.
This research was supported by the State Commission for Higher Education of the Russian Federation under grant No. 2-16-5-31
and by the Russian Foundation for Basic Research under grant No. 93-011-196. 相似文献
2.
I. I. Sharapudinov 《Mathematical Notes》1997,62(4):501-512
Suppose that 0<δ≤1,N=1/δ, and α, ga≥0, is an integer. For the classical Meixner polynomials
orthonormal on the gird {0, δ, 2δ, ...} with weight ρ(x)=(1-e
−δ)αг(Nx+α+ 1)/г(Nx+1), the following asymptotic formula is obtained:
. The remainderv
n,N
α
(z) forn≤λN satisfies the estimate
where Λ
k
α
(x) are the Laguerre orthonormal polynomials. As a consequence, a weighted estimate, for the Meixner polynomial
on the semiaxis [0, ∞) is obtained.
Translated fromMatematicheskie Zametki, Vol. 62, No. 4, pp. 603–616, October, 1997.
Translated by N. K. Kulman 相似文献
3.
I. N. Brui 《Mathematical Notes》1997,62(5):566-574
Suppose that a lower triangular matrix μ:[μ
m
(n)
] defines a conservative summation method for series, i.e.,
and the sequence (ρ
m
,m ∈ ℤ0), is bounded away from zero. Then the trigonometric series
is the Fourier series of a functionf ∈L
p
(
), wherep ε ]1; ∞[, if and only if the sequence ofp-norms of its μ-means is bounded:
In the case of the Fejér method, we have the test due to W. and G. Young (1913). In the case of the Fourier method, we obtain
the converse of the Riesz theorem (1927).
Translated fromMatematicheskie Zametki, Vol. 62, No. 5, pp. 677–686, November, 1997.
Translated by N. K. Kulman 相似文献
4.
Mihai Mihăilescu 《Czechoslovak Mathematical Journal》2008,58(1):155-172
We study the boundary value problem in Ω, u = 0 on ∂Ω, where Ω is a smooth bounded domain in ℝ
N
. Our attention is focused on two cases when , where m(x) = max{p
1(x), p
2(x)} for any x ∈ or m(x) < q(x) < N · m(x)/(N − m(x)) for any x ∈ . In the former case we show the existence of infinitely many weak solutions for any λ > 0. In the latter we prove that if λ is large enough then there exists a nontrivial weak solution. Our approach relies on the variable exponent theory of generalized
Lebesgue-Sobolev spaces, combined with a ℤ2-symmetric version for even functionals of the Mountain Pass Theorem and some adequate variational methods. 相似文献
5.
V. G. Zhuravlev 《Journal of Mathematical Sciences》2006,137(2):4658-4672
For the two-dimensional torus
, we construct the Rauzy tilings d0 ⊃ d1 ⊃ … ⊃ dm ⊃ …, where each tiling dm+1 is obtained by subdividing the tiles of dm. The following results are proved. Any tiling dm is invariant with respect to the torus shift S(x) = x+
mod ℤ2, where ζ−1 > 1 is the Pisot number satisfying the equation x3− x2−x-1 = 0. The induced map
is an exchange transformation of Bmd ⊂
, where d = d0 and
. The map S(m) is a shift of the torus
, which is affinely isomorphic to the original shift S. This means that the tilings dm are infinitely differentiable. If ZN(X) denotes the number of points in the orbit S1(0), S2(0), …, SN(0) belonging to the domain Bmd, then, for all m, the remainder rN(Bmd) = ZN(Bmd) − N ζm satisfies the bounds −1.7 < rN(Bmd) < 0.5. Bibliography: 10 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 322, 2005, pp. 83–106. 相似文献
6.
In the paper we study a binding boundary value problem for two media for Poisson's equation μΔu=f(x) with solutions in the class
, 1<p<∞, with the corresponding seminorm, where
It is proved that the solution exists for allf(x)∈L
p
, anda priori estimates of the solution are obtained with the help of multiplicators in the space
. An explicit solution of the problem for all
is obtained. The kernel of the operator generated by the problem is constructed (in explicit form) as a polynomial of the
first degree.
Translated fromMatematicheskie Zametki, Vol. 66, No. 4, pp. 515–526, October, 1999. 相似文献
7.
Michel Talagrand 《Israel Journal of Mathematics》1999,111(1):275-284
Consider the discrete cube Ω={0,1}
N
, provided with the uniform probabilityP. We denote byd(x, A) the Hamming distance of a pointx of Ω and a subsetA of Ω. We define the influenceI(A) of theith coordinate onA as follows. Forx in Ω, consider the pointT
i
(x) obtained by changing the value of theith coordinate. Then
We prove that we always have
Since it is easy to see that
, this recovers the well known fact that ∫Ω
d(x, A)dP(x) is at most of order
whenP(A)≥1/2. The new information is that ∫Ω
d(x, A)dP(x) can be of order
only ifA reassembles the Hamming ball {x; ∑1≤N
x
i
≥N/2}. 相似文献
8.
M. I. Anokhin 《Mathematical Notes》1997,61(1):3-8
LetF be a free group with at most countable system
of free generators, letR be its normal subgroup recursively enumerable with respect to
, and let
be a variety of groups that differs from
and for which the corresponding verbal subgroupV of the free group of countable rank is recursive. It is proved that the word problem inF/V(R) is solvable if and only if this problem is solvable inF/R, and if
, then there exists anR such, that the conjugacy problem inF/R is solvable, but this problem is unsolvable inF/V(R) for any Abelian variety
(all algorithmic problems are regarded with respect to the images of
under the corresponding natural epimorphisms).
Translated fromMatematicheskie Zametki, Vol. 61, No. 1, pp. 3–9, January, 1997.
Translated by M. I. Anokhin 相似文献
9.
Wlodzimier Greblicki Miroslaw Pawlak 《Annals of the Institute of Statistical Mathematics》1985,37(1):443-454
Summary In the paper we estimate a regressionm(x)=E {Y|X=x} from a sequence of independent observations (X
1,Y
1),…, (X
n, Yn) of a pair (X, Y) of random variables. We examine an estimate of a type
, whereN depends onn andϕ
N is Dirichlet kernel and the kernel associated with the hermite series. Assuming, that E|Y|<∞ and |Y|≦γ≦∞, we give condition for
to converge tom(x) at almost allx, provided thatX has a density. if the regression hass derivatives, then
converges tom(x) as rapidly asO(nC−(2s−1)/4s) in probability andO(n
−(2s−1)/4s logn) almost completely. 相似文献
10.
LiJunjie BianBaojun 《高校应用数学学报(英文版)》2000,15(3):273-280
The following regularity of weak solutions of a class of elliptic equations of the form are investigated. 相似文献
11.
I. N. Kostin 《Journal of Mathematical Sciences》1995,77(3):3195-3198
In this paper the problem of the numerical approximation of the minimal global B-attractor
for a semiflow generated by the Navier-Stokes equations in a two-dimensional bounded domain Ω is considered. The method suggested
here is based on the formula
, where GN is a sequence of compact subsets of L2(Ω),
. The procedure of constructing GN is finite and includes the numerical solution of the Navier-Stokes equations by means of the Galerkin method, together with
an explicit finite-difference discretization in time. Bibliography: 5 titles.
To dear teacher Olga A. Ladyzhenskaya on the occasion of the jubilee
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 200, 1992, pp. 91–97.
Translated by V. I. Ochkur. 相似文献
12.
Bin Heng SONG Huai Yu JIAN 《数学学报(英文版)》2005,21(5):1183-1190
We establish the existence of fundamental solutions for the anisotropic porous medium equation, ut = ∑n i=1(u^mi)xixi in R^n × (O,∞), where m1,m2,..., and mn, are positive constants satisfying min1≤i≤n{mi}≤ 1, ∑i^n=1 mi 〉 n - 2, and max1≤i≤n{mi} ≤1/n(2 + ∑i^n=1 mi). 相似文献
13.
A. Ya. Khelemskii 《Mathematical Notes》1977,21(1):51-54
Let
and
be algebras of local and quasilocal observable spin systems corresponding to the group Zr,
be a differentiation invariant with respect to displacements. The question of representation of D in the form of formal Hamiltonian
formed by the displacements of an elementx ε
is considered. It is shown that such a representation exists if the condition
holds, where
means an element obtained from the elements [TkX,a] by some r-multiple process of summation.
Translated from Matematicheskii Zametki, Vol. 21, No. 1, pp. 93–98, January, 1977. 相似文献
14.
The solvability in anisotropic spaces
, σ ∈ ℝ+, p, q ∈ (1, ∞), of the heat equation ut − Δu = f in ΩT ≡ (0, T) × Ω is studied under the boundary and initial conditions u = g on ST, u|t=0 = u0 in Ω, where S is the boundary of a bounded domain Ω ⊂ ℝn. The existence of a unique solution
of the above problem is proved under the assumptions that
and under some additional conditions on the data. The existence is proved by the technique of regularizers. For this purpose
the local-in-space solvability near the boundary and near an interior point of Ω is needed. To show the local-in-space existence,
the definition of Besov spaces by the dyadic decomposition of a partition of unity is used. This enables us to get an appropriate
estimate in a new and promising way without applying either the potential technique or the resolvent estimates or the interpolation.
Bibliography: 26 titles.
Published in Zapiski Nauchnykh Seminarov POMI, Vol. 348, 2007, pp. 40–97. 相似文献
15.
Yu. Kh. Eshkabilov 《Siberian Advances in Mathematics》2009,19(4):233-244
Let Ω1, Ω2 ⊂ ℝν be compact sets. In the Hilbert space L
2(Ω1 × Ω2), we study the spectral properties of selfadjoint partially integral operators T
1, T
2, and T
1 + T
2, with
$
\begin{gathered} (T_1 f)(x,y) = \int_{\Omega _1 } {k_1 (x,s,y)f(s,y)d\mu (s),} \hfill \\ (T_2 f)(x,y) = \int_{\Omega _2 } {k_2 (x,t,y)f(x,t)d\mu (t),} \hfill \\ \end{gathered}
$
\begin{gathered} (T_1 f)(x,y) = \int_{\Omega _1 } {k_1 (x,s,y)f(s,y)d\mu (s),} \hfill \\ (T_2 f)(x,y) = \int_{\Omega _2 } {k_2 (x,t,y)f(x,t)d\mu (t),} \hfill \\ \end{gathered}
相似文献
16.
Positive Solutions for Semipositone
<Emphasis Type="Italic">m</Emphasis>-point Boundary-value
Problems 总被引:7,自引:0,他引:7
Abstract
Let ξ
i
∈ (0, 1) with 0 <
ξ1 < ξ2 <
··· < ξ
m−2 < 1,
a
i
, b
i
∈ [0,∞) with
and
. We consider the
m-point boundary-value
problem
17.
L. V. Kritskov 《Mathematical Notes》1999,65(4):454-461
Suppose thatА is a nonnegative self-adjoint extension to {
} of the formal differential operator−Δu+q(x)u with potentialq(x) satisfying the condition {
18.
O. P. Filatov 《Mathematical Notes》1999,66(3):348-354
For a continuous almost periodic function
, we show that the function
19.
Alessandra Pagano 《Annali dell'Universita di Ferrara》1993,39(1):1-17
We consider a (possibly) vector-valued function u: Ω→R
N, Ω⊂R
n, minimizing the integral
, whereD
iu=∂u/∂x
i, or some more general functional retaining the same behaviour; we prove higher integrability forDu:D
1u,…,Dn−1u∈Lq, under suitable assumptions ona
i(x).
Sunto Consideriamo una funzione u: Ω→R N, Ω⊂R n che minimizzi l'integrale , doveD iu=∂u/∂xi, o un funzionale con un comportamento simile; sotto opportune ipotesi sua i(x), dimostriamo la seguente maggiore integrabilità perDu:D 1u,…,Dn−1uεLq.相似文献 20.
We consider two-phase metrics of the form ϕ(x, ξ) ≔
, where α,β are fixed positive constants and B
α, B
β are disjoint Borel sets whose union is ℝN, and prove that they are dense in the class of symmetric Finsler metrics ϕ satisfying
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