共查询到20条相似文献,搜索用时 31 毫秒
1.
V. Yu. Popov 《Algebra and Logic》2001,40(1):55-66
It is proved that there exists an infinite sequence of finitely based semigroup varieties
such that, for all i, an equational theory for
and for the class
of all finite semigroups in
is undecidable while an equational theory for
and for the class
of all finite semigroups in
is decidable. An infinite sequence of finitely based semigroup varieties
is constructed so that, for all i, an equational theory for
and for the class
of all finite semigroups in
is decidable whicle an equational theory for
and for the class
of all finite semigroups in
is not. 相似文献
2.
Let
be a computable structure and let R be an additional relation on its domain. We establish a necessary and sufficient condition for the existence of an isomorphic copy
of
such that the image of R
is h-simple (h-immune) relative to
. 相似文献
3.
4.
D. M. Smirnov 《Algebra and Logic》2003,42(2):136-146
We continue to study interrelations between permutative varieties and the cyclic varieties defined by cycles of the form
. A criterion is given determining whether a cyclic variety
is interpretable in
. For a permutation
without fixed elements, it is stated that a set of primes
for which
is interpretable in
in the lattice
is finite. It is also proved that for distinct primes
, the Helly number of a type
in
coincides with dimension of the dual type
and equals
. 相似文献
5.
We prove a theorem on possible test rank values for groups of the form
. It is shown that test rank of a free polynilpotent group
is equal to
or
, for any
and every collection
of classes. Moreover,
for
and
. 相似文献
6.
Suppose that
,
, and
are three discrete probability distributions related by the equation (E):
, where
denotes the k-fold convolution of
In this paper, we investigate the relation between the asymptotic behaviors of
and
. It turns out that, for wide classes of sequences
and
, relation (E) implies that
, where
is the mean of
. The main object of this paper is to discuss the rate of convergence in this result. In our main results, we obtain O-estimates and exact asymptotic estimates for the difference
. 相似文献
7.
Suppose that
is an arbitrary finite complex Borel measure on the interval
is its Poisson integral,
and
are the conjugate harmonics of
, and
is the nontangential limiting value of the analytic function
as
. In this paper, we consider the problem of representing the analytic function
in terms of its boundary values
. 相似文献
8.
A. N. Petrov 《Journal of Mathematical Sciences》2001,107(4):4067-4072
A new numerical inequality for average power means is presented. Let
and let
be a sequence of positive numbers. Consider the operator
. We denote by
the superposition of these operators. The following assertion is proved: if
. Bibliography: 2 titles. 相似文献
9.
If a regular graph of valence
and diameter
has
vertices, then
, which was proved by Moore (cf. [1]). Graphs for which this non-strict inequality turns into an equality are called Moore graphs. Such have an odd girth equal to
. The simplest example of a Moore graph is furnished by a
-triangle. Damerell proved that a Moore graph of valence
has diameter 2. In this case
, the graph is strongly regular with
and
, and the valence
is equal to 3 (Peterson's graph), to 7 (Hoffman–Singleton's graph), or to 57. The first two graphs are of rank 3. Whether a Moore graph of valence
exists is not known; yet, Aschbacher proved that the Moore graph with
will not be a rank 3 graph. We call the Moore graph with
the Aschbacher graph. Cameron showed that such cannot be vertex transitive. Here, we treat subgraphs of fixed points of Moore graph automorphisms and an automorphism group of the hypothetical Aschbacher graph for the case where that group contains an involution. 相似文献
10.
This article improves results of Hamada, Helleseth and Maekawa on minihypers in projective spaces and linear codes meeting the Griesmer bound.In [10,12],it was shown that any
-minihyper, with
, where
, is the disjoint union of
points,
lines,...,
-dimensional subspaces. For q large, we improve on this result by increasing the upper bound on
non-square, to
non-square,
square,
, and (4) for
square, p prime, p<3, to
. In the case q non-square, the conclusion is the same as written above; the minihyper is the disjoint union of subspaces. When q is square however, the minihyper is either the disjoint union of subspaces, or the disjoint union of subspaces and one subgeometry
. For the coding-theoretical problem, our results classify the corresponding
codes meeting the Griesmer bound. 相似文献
11.
We show that every computable relation on a computable Boolean algebra
is either definable by a quantifier-free formula with constants from
(in which case it is obviously intrinsically computable) or has infinite degree spectrum. 相似文献
12.
Sorin G> Gal 《Journal of Computational Analysis and Applications》2000,2(3):265-276
Starting from the equivalence between the Ditzian–Totik modulus
and
, where
, in this article large classes of functions
are introduced for which the modulus
can be easily calculated. As a consequence, very good estimates for the bestapproximation are obtained. The attempts to estimate or calculate themodulus
can be a very intricateproblem. 相似文献
13.
Factorizations of One-Generated Composition Formations 总被引:2,自引:0,他引:2
A non-empty formation
of finite groups is said to be solubly saturated, or we call it a composition formation, if every finite group G having a normal subgroup N such that
belongs to
. An intersection of all composition formations containing a given group G is denoted cformG. Conditions are described under which
has the form
, where
. 相似文献
14.
H. Renelt 《Journal of Mathematical Sciences》2003,115(2):2251-2261
By means of an elementary consideration, families of integral transformations in certain spaces (e.g., in
, where
is the unit disk) are constructed. These transformations map elements of certain subspaces either to itself or to their derivatives, respectively. As a special case, we obtain a family of integral transformations generating a decomposition of
into a direct sum. By introducing appropriate new scalar products, these direct sums become decompositions into orthogonal complements, and the corresponding integral transformations become self-adjoint operators of
into itself positive with respect to the new scalar products. In further special cases, these integral transformations possess bounded and injective extensions mapping
onto well-defined subspaces of
. The latter property is a consequence of the connection of our transformations with the complex Hilbert transformation. Bibliography: 10 titles. 相似文献
15.
V. Yu. Popov 《Algebra and Logic》2005,44(1):46-54
There exist independently based semigroup varieties
and
,
, such that
has no cover in the interval [
;
].Translated from Algebra i Logika, Vol. 44, No. 1, pp. 81–96, January–February, 2005. 相似文献
16.
17.
S. Ya. Novikov 《Journal of Mathematical Sciences》2004,120(5):1733-1751
We study operators
(not necessarily linear) defined on a quasi-Bahach space X and taking values in the space of real-valued Lebesgue-measurable functions. Factorization theorems for linear and superlinear operators with values in the space
are proved with the help of the Lorentz sequence spaces
. Sequences of functions belonging to fixed bounded sets in the spaces
are characterized for
and
. The possibility of distinguishing weak type operators (bounded in the space
) from operators factorizable through
is obtained in terms of sequences of independent random variables. A criterion under which an operator is symmetrically bounded in order in
, is established. Some refinements of the above-mentioned results are obtained for translation shift-invariant sets and operators. Bibliography: 30 titles. 相似文献
18.
A celebrated result of Johnson, Maurey, König and Retherford from 1977 states that for
every complex
matrix
satisfies the following eigenvalue estimate:
Based on the concept of entropy numbers and a simple product trick we give a selfcontained elementary proof. 相似文献
19.
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
20.
For an arbitrary function
, we determine the general form of a linear continuous functional on the space C
w
0
. The criterion for denseness of polynomials in the space
established by Hamburger in 1921 is extended to the spaces C
w
0
. 相似文献