共查询到20条相似文献,搜索用时 734 毫秒
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.
O. P. Filatov 《Mathematical Notes》1999,66(3):348-354
For a continuous almost periodic function
, we show that the function
where the supremum is taken over all solutions of the system of differential inclusion
,
, has the following limit (as μ→+0):
, Thus if the parameter μ is small, then
and the limit of the maximal mean can approximately be determined by solving problems of smaller dimensionality. Moreover,
if the compact sets
and
are nondegenerate, then Ψ
f
is independent of initial data.
Translated fromMatematicheskie Zametki, Vol. 66, No. 3, pp. 431–438, September, 1999. 相似文献
3.
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
4.
The paper is concerned with the sharpness of some well-known estimates in universal linear-invariant families
of regular functions. It is shown that the estimate of | arg ƒ′(z)|,z ∈ Δ = {z: |z| < 1} obtained by Pommerenke in 1964 is sharp; the extremal function is found. A lower estimate for the Schwarzian derivative
in
is obtained. For
, a sharp estimate of order of the function ƒr(z)=ƒ(rz)/r withr ∈ (0, 1) is found; this estimate is applied to solve other problems.
Translated fromMatematicheskie Zametki, Vol. 63, No. 5, pp. 665–672, May, 1998. 相似文献
5.
A. Yu. Karlovich 《Mathematical Notes》1998,64(3):330-341
We consider the Banach algebra
of singular integral operators with matrix piecewise continuous coefficients in the reflexive Orlicz spaceL
M
n
(Γ). We assume that Γ belongs to a certain wide subclass of the class of Carleson curves; this subclass includes curves with
cusps, as well as curves of the logarithmic spiral type. We obtain an index formula for an arbitrary operator from the algebra
in terms of the symbol of this operator.
Translated fromMatematicheskie Zametki, Vol. 64, No. 3, pp. 383–396, September, 1998. 相似文献
6.
易法槐 《应用数学学报(英文版)》1998,14(1):48-57
1.IntroductionSuperconductorsofTypeIarematerialswhicharecapableofchangingfromthephaseofbeingnormalconductorstoaphasewherethereisnoresistancetothemotionoffreeelections.InnormalconductorphasethenormalizedMaxwellequations(neglectingdisplacementcurrents)aretogetherwithOhm'slawj~acEwhereuistheelectricconductivity.InasuperconductingphaseOhm'slawisnolongervalidandMaxwell'sequationsaresupplemelltedbytheGinzburg-Landaufieldequationsll].Underisothermalconditions,thechangeofphasefromsuperconductingto… 相似文献
7.
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 {
} or the condition {
} in which the nonnegative function itχ(r) is such that {
}. For each α∈(0, 2], we establish an estimate of the generalized Fourier transforms of an arbitrary function {
} of the form {
} If, in addition, {
}, then, along with this estimate, a similar lower bound is established.
Translated fromMatematicheskie Zametki, Vol. 65, No. 4, pp. 542–551, April, 1999. 相似文献
8.
Josip Globevnik 《Journal of Geometric Analysis》1993,3(3):269-277
LetD ⊂C
N
,N ≥ 2 be a bounded open set withC
2 boundary and letL be an open connected set of affine complex hyperplanes inC
N
containing a hyperplane that misses
. LetE = ∪Λ∈LΛ, Γ =E ∩bD. Suppose thatf ∈C(Γ) and assume that
相似文献
9.
A powerful tool for studying the growth of analytic and harmonic functions is Hall's Lemma, which states that there is a constantC>0 so that the harmonic measure of a subsetE of the closed unit disk
evaluated at 0 satisfies
whereE
rad is the radial projection ofE onto
. FitzGerald, Rodin and Warschawski proved that ifE is a continuum in
whose radial projection has length at most π then (*) is true withC=1, and they asked how large the length, |E
rad|, can be in order for their result to be valid. We prove that (*) holds withC=1 for every continuum
satisfying
and θc cannot be replaced by a larger number. Fuchs asked for the largest constantC so that (*) holds for allE. We show that for every continuum
, (*) holds withC=C
2π≅.977126698498665669…, whereC
2π is the harmonic measure of the two long sides of a 3∶1 rectangle evaluated at the center. There are Jordan curves for which
equality holds in (*) withC=C
2π.
The authors are supported in part by NSF grants DMS-9302823 and DMS-9401027, and while at MSRI by NSF grant DMS-9022140. 相似文献
10.
A. N. Skiba 《Mathematical Notes》1999,65(3):326-330
It is proved that, if
is a singly generated composition formation, where
, then
is a composition formation.
Translated fromMatematicheskie Zametki, Vol. 65, No. 3, pp. 389–395, March, 1999. 相似文献
11.
L. I. Danilov 《Mathematical Notes》1997,61(1):48-57
We consider Stepanov almost periodic functions μ ∈
ranging in the metric space
of Borel probability measures on a complete separable metric space
is equipped with the Prokhorov metric). The main result is as follows: a function
, belongs to
if and only if for each bounded continuous function
, the function
is Stepanov almost periodic (of order 1) and
12.
V. Yu. Popov 《Mathematical Notes》2000,67(4):495-504
An example of a series of varieties of rings
with the finite basis property is constructed for which the word problem in the relatively free ring
of rankn in the variety
is decidable if and only ifn <p.
Translated fromMatematicheskie Zametki, Vol. 67, No. 4, pp. 582–594, April, 2000. 相似文献
13.
For multiplicative functions ƒ(n), let the following conditions be satisfied: ƒ(n)≥0 ƒ(p
r)≤A
r,A>0, and for anyε>0 there exist constants
,α>0 such that
and Σ
p≤x
ƒ(p) lnp≥αx. For such functions, the following relation is proved:
14.
M. Nowak 《Rendiconti del Circolo Matematico di Palermo》1998,47(3):363-374
In 1986 S. Axler [3] proved that forf∈L
a
2
the Hankel operator
is compact if and only iff is in the little Bloch space {itB}{in0}. In this note we show that the same is true for
, 1<p<∞. Moreover we prove that
is ⋆-compact if and only if
as |z|→1−. 相似文献
15.
It is shown that in the spacesA
R
(0 <R ⩽ ∞) of all functions which are single-valued and analytic in the disk |z| < R with the topology of compact convergence,
the differential operator of infinite order with constant coefficients
is equivalent to the operator Dn (n is a fixed natural number) if and only if
and |ϕ
n
| = 1 for R < ∞ or ϕ
n
≠ 0 for R = ∞. Also the equivalence of two shift operators in the space A∞ is investigated.
Translated from Matematicheskie Zametki, Vol. 21, No. 1, pp. 33–37, January, 1977. 相似文献
16.
The paper is devoted to the study of the behavior of the following mixed problem for large values of time:
17.
We obtain a set of necessary and sufficient conditions for
to imply
for 1 <k ≤ s < ∞. Using this result we establish several inclusion theorems as well as conditions for the equivalence of
and
. 相似文献
18.
Yu. F. Korobeinik 《Mathematical Notes》2000,67(4):448-458
LetF ⊂ ℂ be a dense-in-itself set that has a nonempty connected interior and contains the origin, and let
be the space of infinitely differentiable complex-valued functions onF. For some classes of such setsF, we prove that for an arbitrary sequence
of complex numbers there exists a functionf ε
withf
(n)(0)=d
n,n=0, 1, 2, ..., and study the analyticity properties off. The functionf is constructed in the form of various function series, namely, a power series, a series of simple fractions, and an exponential
series. Analytic solutions of the multidimensional Borel problem are also considered.
Translated fromMatematicheskie Zametki, Vol. 67, No. 4, pp. 525–538, April, 2000. 相似文献
19.
A. V. Filinovskii 《Mathematical Notes》1997,61(5):635-643
The following boundary value problem is studied:
20.
V. E. Tarakanov 《Mathematical Notes》1997,62(6):731-738
For the Legendre-Sobolev orthonormal polynomials
depending on the parametersM≥0,N≥0, weighted and uniform estimates on the orthogonality interval are obtained. It is shown that, unlike the Legendre orthonormal
polynomials, the polynomials
forM>0,N>0 decay at the rate ofn
−3/2 at the points 1 and −1. The values of
are calculated.
Translated fromMatematicheskie Zametki, Vol. 62, No. 6, pp. 871–880, December, 1997.
Translated by N. K. Kulman 相似文献
|