共查询到20条相似文献,搜索用时 555 毫秒
1.
Adem Kilicman 《Czechoslovak Mathematical Journal》2001,51(3):463-471
Let
,
be ultradistributions in
and let
and
where
is a sequence in
which converges to the Dirac-delta function
. Then the neutrix product
is defined on the space of ultradistributions
as the neutrix limit of the sequence
provided the limit
exist in the sense that
for all in
. We also prove that the neutrix convolution product
exist in
, if and only if the neutrix product
exist in
and the exchange formula
is then satisfied. 相似文献
2.
In 1997 Ptak defined generalized Hankel operators as follows: Given two contractions
and
, an operator
is said to be a generalized Hankel operator if
and X satisfies a boundedness condition that depends on the unitary parts of the minimal isometric dilations of T
1 and T
2. This approach, call it (P), contrasts with a previous one developed by Ptak and Vrbova in 1988, call it (PV), based on the existence of a previously defined generalized Toeplitz operator. There seemed to be a strong but somewhat hidden connection between the theories (P) and (PV) and we clarify that connection by proving that (P) is more general than (PV), even strictly more general for some T
1 and T
2, and by studying when they coincide. Then we characterize the existence of Hankel operators, Hankel symbols and analytic Hankel symbols, solving in this way some open problems proposed by Ptak. 相似文献
3.
Andreas Rosenschon 《K-Theory》1999,16(2):185-199
Let X be a smooth projective variety over the complex numbers. We consider the cohomology of the sheaves
and
arising from Deligne–Beilinson cohomology and the Hodge filtration on the singular cohomology of X. We show that one can identify
with the image of the truncated regulator map c¯2,1. In particular, this implies that
is countable. Since this group is a direct summand of coker
, this gives a partial answer to Voisin's conjecture that cocker() is countable. In the case of X a surface, we prove that the Albanese kernel T(X) is isomorphic to the group of global sections of
if and only if pg=0. 相似文献
4.
Aderemi Kuku 《K-Theory》2001,22(4):367-392
Let
be a rational prime,
an exact category. In this article, we define and study for all
, the profinite higher K-theory of
, that is
as well as
, where
is the
-dimensional mod-
Moore space. We study connections between
and prove several
-completeness results involving these and associated groups including the cases where
is the category of finitely generated (resp. finitely generated projective) modules over orders in semi-simple algebras over number fields and p-adic fields. We also define and study continuous K-theory
of orders in p-adic semi-simple algebras and show some connection between the profinite and continuous K-theory of . 相似文献
5.
The concepts of an annihilator and a relative annihilator in an autometrized l-algebra are introduced. It is shown that every relative annihilator in a normal autometrized l-algebra
is an ideal of
and every principal ideal of
is an annihilator of
. The set of all annihilators of
forms a complete lattice. The concept of an I-polar is introduced for every ideal I of
. The set of all I-polars is a complete lattice which becomes a two-element chain provided I is prime. The I-polars are characterized as pseudocomplements in the lattice of all ideals of
containing I. 相似文献
6.
Judita Lihová 《Czechoslovak Mathematical Journal》1999,49(1):67-80
Let
be a partially ordered set, Int
the system of all (nonempty) intervals of
partially ordered by the set-theoretical inclusion
. We are interested in partially ordered sets
with Int
isomorphic to Int
. We are going to show that they correspond to couples of binary relations on A satisfying some conditions. If
is a directed partially ordered set, the only
with Int
isomorphic to Int
are
corresponding to direct decompositions
of
(
denotes the dual of
. The present results include those presented in the paper [11] by V. Slavík. Systems of intervals, particularly of lattices, have been investigated by many authors, cf. [1]–[11]. 相似文献
7.
J. E. Marcos 《Czechoslovak Mathematical Journal》2003,53(3):689-706
We define various ring sequential convergences on
and
. We describe their properties and properties of their convergence completions. In particular, we define a convergence
on
by means of a nonprincipal ultrafilter on the positive prime numbers such that the underlying set of the completion is the ultraproduct of the prime finite fields
Further, we show that
is sequentially precompact but fails to be strongly sequentially precompact; this solves a problem posed by D. Dikranjan. 相似文献
8.
In the open disk
of the complex plane, we consider the following spaces of functions: the Bloch space
; the Hardy--Sobolev space
; and the Hardy--Besov space
. It is shown that if all the poles of the rational function R of degree n,
, lie in the domain
, then
, where
and
depends only on
. The second of these inequalities for the case of the half-plane was obtained by Semmes in 1984. The proof given by Semmes was based on the use of Hankel operators, while our proof uses the special integral representation of rational functions. 相似文献
9.
We prove new pointwise inequalities involving the gradient of a function
, the modulus of continuity
of the gradient
, and a certain maximal function
and show that these inequalities are sharp. A simple particular case corresponding to
and
is the Landau type inequality
, where the constant 8/3 is best possible and
. 相似文献
10.
Avishay Vaknin 《K-Theory》2001,24(1):57-68
For a small triangulated category
, Bass's K
1 group
is described, and the theorem of the heart is proved. We define the determinant map from
to Neeman's
, and we compute this map when
is the derived category of an Abelian category
. 相似文献
11.
Let R
3 be a bounded domain,
0$$
" align="middle" border="0">
, a family of extending subdomains, and =(x) a positive function in
be a space of -solenoidal vector fields,
0$$
" align="middle" border="0">
, a family of subspaces, G orthogonal projectors in
onto
. A unitary transformation that diagonalizes the family of projectors {G} is constructed: it takes
to the operator of multiplication by the independent variable. The isometry of this transformation is proved with the help of the operator Riccati equation for the NeumanntoDirichlet mapping. Bibliography: 8 titles. 相似文献
12.
F. G. Abdullayev 《Czechoslovak Mathematical Journal》2001,51(3):643-660
Let C be the extended complex plane; G C a finite Jordan with 0 G; w= (z) the conformal mapping of G onto the disk
normalized by
. Let us set
, and let
be the generalized Bieberbach polynomial of degree n for the pair (G,0), which minimizes the integral
in the class of all polynomials of degree not exceeding n with
. In this paper we study the uniform convergence of the generalized Bieberbach polynomials
with interior and exterior zero angles and determine its dependence on the properties of boundary arcs and the degree of their tangency. 相似文献
13.
The 3-local geometry
of the sporadic simple group Co1 has been known to have a cover
with a flag-transitive automorphism group which is a nonsplit extension of an elementary Abelian 2-group of rank 24 (the Leech lattice modulo 2) by Co1. It was conjectured that
was simply connected. We disprove this conjecture by constructing a double cover
of
. The automorphism group of
is of the shape
. However, it is not isomorphic to the involution centralizer of the Monster sporadic simple group. 相似文献
14.
P. M. Akhmet'ev 《Journal of Mathematical Sciences》2004,119(1):5-9
Pairs B,
of divergence-free vector fields with compact support in
are considered higher-order analog M(B,
c (of order 3) of the Gauss helicity number H(B,
)=
, curl(A)=B; (of order 1) is constructed, which is invariant under volume-preserving diffeomorphisms. An integral expression for M is given. A degree-four polynomial m(B(x1), B(x2),
(
1),
(
2)), x1, x2,
1
2
, is defined, which is symmetric in the first and second pairs of variables separately. M is the average value of m over arbitrary configurations of points. Several conjectures clarifying the geometric meaning of the invariant and relating it to invariants of knots and links are stated. Bibliography: 11 titles. 相似文献
15.
Dong Zhe 《Czechoslovak Mathematical Journal》2006,56(2):287-298
In this paper we investigate finite rank operators in the Jacobson radical
of Alg(
), where
are nests. Based on the concrete characterizations of rank one operators in Alg(
) and
, we obtain that each finite rank operator in
can be written as a finite sum of rank one operators in
and the weak closure of
equals Alg(
) if and only if at least one of
is continuous. 相似文献
16.
P. M. G. Manchón 《Czechoslovak Mathematical Journal》2002,52(1):1-9
In this paper we study the hypersurfaces
given as connected compact regular fibers of a differentiable map
, in the cases in which
has finitely many nondegenerate critical points in the unbounded component of
. 相似文献
17.
B. Yousefi 《Czechoslovak Mathematical Journal》2004,54(1):261-266
Let
be a sequence of positive numbers and 1 p< . We consider the space H
p() of all power series
such that
. We investigate strict cyclicity of
the weakly closed algebra generated by the operator of multiplication by zacting on H
p(), and determine the maximal ideal space, the dual space and the reflexivity of the algebra
. We also give a necessary condition for a composition operator to be bounded on H
p() when
is strictly cyclic. 相似文献
18.
Márcia Federson 《Czechoslovak Mathematical Journal》2002,52(2):429-437
We prove two versions of the Monotone Convergence Theorem for the vector integral of Kurzweil,
, where R is a compact interval of
, and f are functions with values on L(Z,W) and Z respectively, and Z and W are monotone ordered normed spaces. Analogous results can be obtained for the Kurzweil vector integral,
, as well as to unbounded intervals R. 相似文献
19.
Ján Jakubík 《Czechoslovak Mathematical Journal》2002,52(3):651-663
Let Int
be the lattice of all intervals of an MV-algebra
. In the present paper we investigate the relations between direct product decompositions of
and (i) the lattice Int
, or (ii) 2-periodic isometries on
, respectively. 相似文献
20.
O. L. Vinogradov 《Journal of Mathematical Sciences》2001,107(4):3987-4001
In what follows, C is the space of
-periodic continuous real-valued functions with uniform norm,
is the first continuity modulus of a function
with step h, H
n is the set of trigonometric polynomials of order at most n,
is the set of linear positive operators
(i.e., of operators such that
for every
),
is the space of square-integrable functions on
,
It is proved that
coincides with the smallest eigenvalue of some matrix of order n+1. The main result of the paper states that, for every
does not exceed and, for
, is equal to the minimum of the quadratic functional
over the unit sphere of
. Then it is calculated that
Bibliography: 19 titles. 相似文献