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1.
G. L. Booth 《Periodica Mathematica Hungarica》1991,22(3):175-182
The Brown-McCoy radical
is known to be an ideal-hereditary Kurosh-Amitsur radical in the variety of zerosymmetric near-rings. We define the Brown-McCoy and simplical radicals,
and
, respectively, for zerosymmetric -near-rings. Both
and
are ideal-hereditary Kurosh-Amitsur radicals in that variety. IfM is a zerosymmetric -near-ring with left operator near-ringL, it is shown that
, with equality ifM has a strong left unity.
is extended to the variety of arbitrary near-rings, and
and
are extended to the variety of arbitrary -near-rings, in a way that they remain Kurosh-Amitsur radicals. IfN is a near-ring andA N, then
, with equality ifA if left invariant. 相似文献
2.
LetT be a contraction acting in a separable Hilbert space
and leaving invariant a nest
of subspaces of
. We answer the question: when doesT have an isometric extension to
which leaves invariant the nest
= {N N :N
;}. 相似文献
3.
Let (G,
) denote a finite groupG with fibration
. The group Aut (G,
) of operators of (G,
) is closely related to the group of collineations of (G,
). In this paper we investigate the geometric properties imposed on (G,
) by requiring that Aut (G,
)=AutG. We find that in many instances this algebraic property restricts the geometry to a very special form.Dedicated to Professor Helmut Karzel on the occasion of his 60th birthday. 相似文献
4.
LetS be a 0-distributive semilattice and
be its minimal spectrum. It is shown that
is Hausdorff. The compactness of
has been characterized in several ways. A representation theorem (like Stone's theorem for Boolean algebras) for disjunctive, 0-distributive semilattices is obtained. 相似文献
5.
Roman Drnovšek 《Integral Equations and Operator Theory》2001,39(3):253-266
Let
be a collection of bounded operators on a Banach spaceX of dimension at least two. We say that
is finitely quasinilpotent at a vectorx
0X whenever for any finite subset
of
the joint spectral radius of
atx
0 is equal 0. If such collection
contains a non-zero compact operator, then
and its commutant
have a common non-trivial invariant, subspace. If in addition,
is a collection of positive operators on a Banach lattice, then
has a common non-trivial closed ideal. This result and a recent remarkable theorem of Turovskii imply the following extension of the famous result of de Pagter to semigroups. Let
be a multiplicative semigroup of quasinilpotent compact positive operators on a Banach lattice of dimension at least two. Then
has a common non-trivial invariant closed ideal.This work was supported by the Research Ministry of Slovenia. 相似文献
6.
Xingde Dai 《Integral Equations and Operator Theory》1997,27(3):294-313
Let be a nest in a separably acting factor
. We present conditions for a factor
to be a bimodule of the nest subalgebraalgß in
which is singly generated in the norm topology. Some relevant results about the compact ideal
, the quasitriangular algebra and the Calkin algebra are established.This work was supported, in part, by funds provided by the University of North Carolina at Charlotte. 相似文献
7.
Let
and
the foliations by the null geodesics of some lorentzian metricg on the torus
. We analyse how geodesic completeness properties ofg are related to the dynamics of
and
. 相似文献
8.
Scott McCullough 《Integral Equations and Operator Theory》2001,39(3):335-362
Let
denote an annulus,E a finite subset of
with at least three elements, and
the ideal of functions in
which vanish at the points ofE. The quotient
does not have a completely isometric representation on a finite dimensional Hilbert space. This complements a result of [11] which implies that the quotient has an isometric representation on a Hilbert space of dimension twice the cardinality ofE. 相似文献
9.
Necdet Güner 《Geometriae Dedicata》1996,63(1):17-23
Let N=G/ be a compact nilmanifold, G a connected, simply connected, nilpotent Lie group with its discrete subgroup and Lie algebra
. Let I* (
) denote the invariant differential forms on
.If I* (
) H* (
) is an injective map, then G is abelian and N is a torus. Furthermore, N has a formal minimal model. If N is an even-dimensional compact nilmanifold, it has a Kähler structure and invariant symplectic structure if and only if I* (
) H* (
) is injective. 相似文献
10.
Johannes Ueberberg 《Journal of Geometry》1990,37(1-2):171-180
Generalizing a theorem of Beutelspacher and Seeger, we consider line sets
inP=PG(2t + 1,q),t IN, with the following properties: (1) any (t + 1)-dimensional subspace ofP contains at least one line of
, (2) if a pointx ofP is incident with at least two lines of
then the points in the factor geometryP/x which are induced by the lines of
throughx form a blocking set of type (t, 1) inP/x, (3) any line of
is coplanar with at least one further line of
. We will show that the examples of minimal cardinality are exactly the line sets of Baer subspaces ofP. 相似文献
11.
Marilyn Breen 《Geometriae Dedicata》1996,60(3):283-288
Let
be a family of simple polygons in the plane. If every three (not necessarily distinct) members of
have a simply connected union and every two members of
have a nonempty intersection, then {P:P in
}
. Applying the result to a finite family
of orthogonally convex polygons, the set {C:C in
} will be another orthogonally convex polygon, and, in certain circumstances, the dimension of this intersection can be determined.Supported in part by NSF grant DMS-9207019. 相似文献
12.
Günter Mayer 《Numerische Mathematik》1985,46(1):69-83
Summary Let
be a real irreduciblen×n interval matrix. Then a necessary and sufficient condition is given for the sequence
of the powers of an interval matrix
to converge to a matrix
which is not the null matrix. In addition a criterion for
is proved to decide whether the limit matrix
satisfies the condition of symmetry
. 相似文献
13.
Gerd Herzog 《Periodica Mathematica Hungarica》1995,30(3):205-210
Given a sequence (
n
)
n
in
with
there are functions
such that
, is a dense subset of
, and the set of functions with this property is residual in
. We will show that in
and some related Banach spaceX there are functionsf with
is dense in
, and we will give a sufficient condition when the set of such functions is residual inX. 相似文献
14.
John Harding 《Order》1993,10(3):283-294
If
is a variety of orthomodular lattices generated by a set of orthomodular lattices having a finite uniform upper bound om the length of their chains, then the MacNeille completion of every algebra in
again belongs to
.The author gratefully acknowledges the support of NSERC. 相似文献
15.
The largest Fischer 3-transposition group M(24) acts flag-transitively on a 3-local incidence geometry
(M(24)) which is a c-extension of the dual polar space associated with the group O
7(3). The action of the simple commutator subgroup M(24) is still flag-transitive. We show that
(M(24)) is characterized by its diagram under the flag-transitivity assumption. The result implies in particular that
(M(24)) is simply connected. The geometry
(M(24)) appears as a subgeometry in the Buekenhout-Fischer 3-local geometry
(F
1) of the Monster group. The simple connectedness of
(M(24)) has played a crucial role in the characterization of
(F
1), which has been achieved recently. When determining the possible structure of the parabolic subgroups we have used an unpublished pushing-up result by U. Meierfrankenfeld.Dedicated to Professor B. Fischer on the occasion of his sixtieth birthday 相似文献
16.
William M. McGovern 《Inventiones Mathematicae》1989,97(1):209-217
Summary LetG be a complex semisimple algebraic group with Lie algebra
. Let
be a nilpotentG-orbit,
its ring of regular functions. We derive a formula for
as aG-module and prove some partial results on
a cover of
. We then relate this formula to various existing multiplicity formulas forK-types in Harish-Chandra bimodules ofG.Supported by National Science Foundation Grant DMS-8505550 相似文献
17.
Koji Furuta 《Integral Equations and Operator Theory》1994,19(4):381-403
We study completion problems of partial matrices associated with a graph where entries are completely bounded maps on aC
*-algebra. We characterize a graph
for which every
-partial completely positive matrix has a completely positive completion. As a special case we study
-partial functional matrices. We give a necessary and sufficient condition for a
-partial functional matrix to have a positive completion and a representation for such matrices. These generalize some results on inflated Schur product maps due to Paulsen, Power and Smith. As an application, we study completely positive completions of partial matrices whose entries are completely bounded multipliers of the Fourier algebra of a locally compact group. 相似文献
18.
Takuya Hara 《Integral Equations and Operator Theory》1992,15(4):551-567
Let
be a Hilbert space. A continuous positive operatorT on
uniquely determines a Hilbert space
which is continuously imbedded in
and for which
with the canonical imbedding
. A Kreîn space version of this result, however, is not valid in general. This paper provides a necessary and sufficient condition for that a continuous selfadjoint operatorT uniquely determines a Kreîn space (
) which is continuously imbedded in
and for which
with the canonical imbedding
. 相似文献
19.
A. I. Budkin 《Algebra and Logic》2000,39(6):363-369
Let
be a class of all groups G for which the normal closure (x)
G
of every element x belongs to a class
.
is a Levi class generated by
. Let
and
0 be classes of finitely generated nilpotent groups and of torsion-free, finitely generated, nilpotent groups, respectively. We prove that
and
, and so
and
. It is shown that quasivarieties
and
are closed under free products, and that each contains at most one maximal proper subquasivariety. It is also proved that
is closed under free products if so is
. 相似文献
20.
We give an example of a complete commutative unitary and semi-simple topological algebra, which is a locally convex inductive limit of an increasing sequence of Fréchet algebras (
algebra), and which contains the field (X) of rational functions; so it contains elements which have empty spectrum and therefore does not contain any character, neither continuous nor non-continuous. This unitary algebra is not a division algebra, so it contains at least one non-trivial maximal ideal; but none of its maximal ideals is closed and they all have infinite codimension. The Gelfand-Mazur Theorem remains therefore unknown for
algebras. 相似文献