共查询到20条相似文献,搜索用时 31 毫秒
1.
Juraj Činčura 《Applied Categorical Structures》1998,6(4):527-530
Let
be an epireflective subcategory of the category Top of topological spaces which is not contained in the category of indiscrete spaces (e.g. Top, the category of Hausdorff spaces, the category of Tychonoff spaces) and
be a coreflective subcategory of
. In this paper we prove that the coreflector
preserves regular epimorphisms if and only if
or
is contained in the category of discrete spaces. 相似文献
2.
This work is a complement to the authors earlier papers, where it is shown that a functor category
inherits from
such properties as amalgamation, transferability and congruence extension if
has either products or certain pushouts. A general scheme is given for constructing counter-examples which show that the latter condition on
is essential. In particular, it is shown that the functor categories
,
,
(
resp.) do not satisfy the amalgamation (congruence extension resp.) property in general. Moreover, one class of categories is described, where the condition of the existence of certain pushouts is not only sufficient, but also necessary for
to preserve the considered properties of
.Mathematics Subject Classifications (2000) 18A25, 18A32, 18B99, 08B26.Dali Zangurashvili: The support rendered by INTAS Grant 97 31961 is gratefully acknowledged. 相似文献
3.
Given any R-semimodule M equipped with a semitopology
we construct an N-protosummation
for M. If
satisfies certain properties, then a similar construction leads to an unconditional N-summation
for M, that is an N-summation for M equipped with the trivial prenorm MD over the N-summation (DN,D) for D. Conversely any N-protosummation
on M gives rise to a topology
. If both
and
satisfy a certain separation property, then
and
form a Galois connection.
Dedicated to my friend and collegue Nico Pumplün on the occasion of his 70th birthdayMathematics Subject Classifications (2000) 16Y60, 54A05. 相似文献
4.
Applying (enriched) categorical structures we define the notion of ordered sheaf on a quantaloid
, which we call ‘
-order’. This requires a theory of semicategories enriched in the quantaloid
, that admit a suitable Cauchy completion. There is a quantaloid
of
-orders and ideal relations, and a locally ordered category
of
-orders and monotone maps; actually,
. In particular is
, with Ω a locale, the category of ordered objects in the topos of sheaves on Ω. In general
-orders can equivalently be described as Cauchy complete categories enriched in the split-idempotent completion of
. Applied to a locale Ω this generalizes and unifies previous treatments of (ordered) sheaves on Ω in terms of Ω-enriched structures.Mathematics Subject Classifications (2000) 06F07, 18B35, 18D05, 18D20. 相似文献
5.
Thomas Scanlon 《Inventiones Mathematicae》2006,163(1):191-211
We prove a p-adic version of the André-Oort conjecture for subvarieties of the universal abelian varieties. Let g and n be integers with n≥3 and p a prime number not dividing n. Let R be a finite extension of
, the ring of Witt vectors of the algebraic closure of the field of p elements. The moduli space
of g-dimensional principally polarized abelian varieties with full level n-structure as well as the universal abelian variety
over
may be defined over R. We call a point
R-special if
is a canonical lift and ξ is a torsion point of its fibre. Employing the model theory of difference fields and work of Moonen
on special subvarieties of
, we show that an irreducible subvariety of
containing a dense set of R-special points must be a special subvariety in the sense of mixed Shimura varieties. 相似文献
6.
We show that for a variety
of Heyting algebras the following conditions are equivalent: (1)
is locally finite; (2) the
-coproduct of any two finite
-algebras is finite; (3) either
coincides with the variety of Boolean algebras or finite
-copowers of the three element chain
are finite. We also show that a variety
of Heyting algebras is generated by its finite members if, and only if,
is generated by a locally finite
-algebra. Finally, to the two existing criteria for varieties of Heyting algebras to be finitely generated we add the following
one:
is finitely generated if, and only if,
is residually finite.
Received November 11, 2001; accepted in final form July 25, 2005. 相似文献
7.
8.
We define the reduced minimum modulus
of a nonzero element a in a unital C
*-algebra
by
. We prove that
. Applying this result to
and its closed two side ideal
, we get that dist
,
and
for any
if RR
= 0, where
and
is the quotient homomorphism and
. These results generalize corresponding results in Hilbert spaces. 相似文献
9.
Yves Felix Jean-Claude Thomas Micheline Vigué-Poirrier 《Publications Mathématiques de L'IHéS》2004,99(1):235-252
Let M be a closed orientable manifold of dimension d and
be the usual cochain algebra on M with coefficients in a field k. The Hochschild cohomology of M,
is a graded commutative and associative algebra. The augmentation map
induces a morphism of algebras
. In this paper we produce a chain model for the morphism I. We show that the kernel of I is a nilpotent ideal and that the image of I is contained in the center of
, which is in general quite small. The algebra
is expected to be isomorphic to the loop homology constructed by Chas and Sullivan. Thus our results would be translated in terms of string homology. 相似文献
10.
Let
be a family of unit balls in
with the property that the mutual distances of the centers are at least
. If any n2 members of
have a common line transversal, then
has a line transversal too.
Received: 27 January 2005; revised: 17 October 2005 相似文献
11.
Lutz Strüngmann 《Archiv der Mathematik》2006,86(3):193-204
Let R be a unital associative ring and
two classes of left R-modules. In this paper we introduce the notion of a
In analogy to classical cotorsion pairs as defined by Salce [10], a pair
of subclasses
and
is called a
if it is maximal with respect to the classes
and the condition
for all
and
Basic properties of
are stated and several examples in the category of abelian groups are studied.
Received: 17 March 2005 相似文献
12.
V. N. Temlyakov 《Advances in Computational Mathematics》2007,26(4):431-449
We study convergence and rate of convergence of expansions of elements in a Banach space X into series with regard to a given dictionary
. For convenience we assume that
is symmetric:
implies
. The primary goal of this paper is to study representations of an element f∈X by a series
In building such a representation we should construct two sequences: {g
j
(f)}
j=1∞
and {c
j
(f)}
j=1∞
. In this paper the construction of {g
j
(f)}
j=1∞
will be based on ideas used in greedy-type nonlinear approximation. This explains the use of the term greedy expansion. We use a norming functional
of a residual f
m−1
obtained after m−1 steps of an expansion procedure to select the mth element
from the dictionary. This approach has been used in previous papers on greedy approximation. The greedy expansions in Hilbert
spaces are well studied. The corresponding convergence theorems and estimates for the rate of convergence are known. Much
less is known about greedy expansions in Banach spaces. The first substantial result on greedy expansions in Banach spaces
has been obtained recently by Ganichev and Kalton. They proved a convergence result for the L
p
, 1<p<∞, spaces. In this paper we find a simple way of selecting coefficients c
m
(f) that provides convergence of the corresponding greedy expansions in any uniformly smooth Banach space. Moreover, we obtain
estimates for the rate of convergence of such greedy expansions for
– the closure (in X) of the convex hull of
.
This research was supported by the National Science Foundation Grant DMS 0200187 and by ONR Grant N00014-91-J1343. 相似文献
13.
Abstract
By
we denote the set of all propositional formulas. Let
be the set of all clauses. Define
. In Sec. 2 of this paper we prove that for normal modal logics
, the notions of
-expansions and
-expansions coincide. In Sec. 3, we prove that if I consists of default clauses then the notions of
-expansions for I and
-expansions for I coincide. To this end, we first show, in Sec. 3, that the notion of
-expansions for I is the same as that of
-expansions for I.
The project is supported by NSFC 相似文献
14.
In our previous work, we introduced a bijection between the elements of the crystal base of the negative (resp. positive)
part of the quantized universal enveloping algebra
of a Kac–Moody algebra
that are fixed by a diagram automorphism and the elements of the crystal base of the negative (resp. positive) part of the
quantized universal enveloping algebra
of the orbit Lie algebra
of
. In this paper, we prove that this bijection commutes with the *-operation. As an application of this result we show that
there exists a canonical bijection between the elements ℬ0(λ) of the crystal base ℬ(λ) of an extremal weight module of extremal weight λ over
that are fixed by a diagram automorphism and the elements of the crystal base
of an extremal weight module of extremal weight
over
, if the crystal graph of
is connected.
Presented by P. Littelmann
Mathematics Subject Classifications (2000) Primary: 17B37, 17B10; secondary: 81R50. 相似文献
15.
Let k 1 and
be a system of rational functions forming a strongly linearly independent set over a finite field
. Let
be arbitrarily prescribed elements. We prove that for all sufficiently large extensions
, there is an element
of prescribed order such that
is the relative trace map from
onto
We give some applications to BCH codes, finite field arithmetic and ordered orthogonal arrays. We also solve a question of Helleseth et~al. (Hypercubic 4 and 5-designs from Double-Error-Correcting codes, Des. Codes. Cryptgr. 28(2003). pp. 265–282) completely.classification 11T30, 11G20, 05B15 相似文献
16.
Alina Iacob 《Archiv der Mathematik》2005,85(4):335-344
We consider two pairs of complete hereditary cotorsion theories
on the category of left R-modules, such that
We prove that for any left R-modules M, N and for any n ≧ 1, the generalized Tate cohomology modules
can be computed either using a left
of M and a left
of M or using a right
a right
of N.
Received: 17 December 2004 相似文献
17.
Congruence properties in congruence permutable and in ideal determined varieties, with applications.
C. J. van. Alten 《Algebra Universalis》2005,53(4):433-449
We define a weak version of EDPC (equationally definable principal congruences), called EDPC*, that is shown to be preserved under varietal closure in congruence permutable varieties. We show that if
is a congruence permutable variety generated by a class
then
has EDPC iff
has EDPC* iff
has EDPC*. An equational condition is given which, if satisfied by
implies that
has the CEP (congruence extension property). Similar results are proved for ideal determined varieties. These results are applied to the variety of residuated lattices, with examples.Received January 15, 2004; accepted in final form October 8, 2004. 相似文献
18.
We prove a product formula which involves the unitary group generated by a semibounded self-adjoint operator and an orthogonal projection P on a separable Hilbert space
with the convergence in
It gives a partial answer to the question about existence of the limit which describes quantum Zeno dynamics in the subspace Ran P. The convergence in
is demonstrated in the case of a finite-dimensional P. The main result is illustrated in the example where the projection corresponds to a domain in
and the unitary group is the free Schrödinger evolution.submitted 21/06/04, accepted 12/10/04 相似文献
19.
20.
Jürgen Elstrodt 《Mathematische Semesterberichte》2005,52(2):197-219
Zusammenfassung Die Funktion
genügt für jedes
der Funktionalgleichung
Wir zeigen, daß jede stetige Lösung
zweier in geeignetem Sinne ,,unabhängiger“ Funktionalgleichungen obigen Typs notwendig von der Form
mit konstanten
ist. ,,Exotische“ Beispiele zeigen, daß dabei auf die Forderung der Unabhängigkeit nicht verzichtet werden kann. – Zusätzlich behandeln wir die Eigenwerttheorie von Mittelwertoperatoren, wie sie auf der rechten Seite der obigen Funktionalgleichung auftreten. Holger Petersson in alter Verbundenheit gewidmet 相似文献