共查询到20条相似文献,搜索用时 31 毫秒
1.
Let M be a right R-module,
the class of all M-small modules, and P a projective cover of M in
[M]. We consider the torsion theories
= (
),
= (
), and
= (
) in
[M], where
is the torsion theory generated by
is the torsion theory cogenerated by
, and
is the dual Lambek torsion theory. We study some conditions for
to be cohereditary, stable, or split, and prove that Rej(M,
) = M
=
(=
=
)
=
GenM(P)
.2000 Mathematics Subject Classification: 16S90 相似文献
2.
Minimum-Volume Enclosing Ellipsoids and Core Sets 总被引:3,自引:0,他引:3
We study the problem of computing a (1+ε)-approximation to the minimum-volume enclosing ellipsoid of a given point set
. Based on a simple, initial volume approximation method, we propose a modification of the Khachiyan first-order algorithm. Our analysis leads to a slightly improved complexity bound of
operations for
. As a byproduct, our algorithm returns a core set
with the property that the minimum-volume enclosing ellipsoid of
provides a good approximation to that of
. Furthermore, the size of
depends on only the dimension d and ε, but not on the number of points n. In particular, our results imply that
for
.We thank the Associate Editor and an anonymous referee for handling our paper efficiently and for helpful comments and suggestions.This author was supported in part by NSF through Grant CCR-0098172.This author was supported in part by NSF through CAREER Grant DMI-0237415. 相似文献
3.
Let
be the Poisson point process with intensity 1 in Rd and let
be
. We obtain a strong invariance principle for the total length of the nearest-neighbor graph on
. 相似文献
4.
Naser Zamani 《Archiv der Mathematik》2006,86(4):321-330
Let
be a homogeneous Noetherian ring with local base ring (R0,m0) and let M,N be two finitely generated graded R-modules. Let
denote the i-th graded generalized local cohomology of N relative to M with support in
. We study the vanishing, tameness and asymptotical stability of the homogeneous components of
.
Received: 22 March 2005; revised: 25 June 2005 相似文献
5.
Frank Müller 《Calculus of Variations and Partial Differential Equations》2005,24(3):283-288
Let $P={\rm \Gamma}\cap{\cal S}Let
be the point of non-tangential intersection of a closed Jordan arc
and an embedded, regular support surface
. Let
be a conformally parametrized solution of
with partially free boundaries
. It is proved, that
is H?lder continuous up to
with
, whenever
meets
orthogonally along its free trace. This provides a regularity result for stationary minimal surfaces and is applicable also
to surfaces of prescribed bounded mean curvature.
Mathematics Subject Classification (2000) 53 A 10, 35 J 65, 35 R 35, 49 Q 05 相似文献
6.
Jaeyoung Byeon Junsang Park 《Calculus of Variations and Partial Differential Equations》2005,24(4):459-477
Let
be a connected compact smooth Riemannian manifold of dimension
with or without smooth boundary
We consider the following singularly perturbed nonlinear elliptic problem on
where
is the Laplace-Beltrami operator on
,
is an exterior normal to
and a nonlinearity
of subcritical growth. For certain
there exists a mountain pass solution
of above problem which exhibits a spike layer. We are interested in the asymptotic behaviour of the spike layer.
Without any non-degeneracy condition and monotonicity of
we show that if
the peak point
of the solution
converges to a maximum point of the scalar curvature
on
(the mean curvature
on
as
respectively.
The research of the first author was supported in part by KRF-2002-070-C000005 of Korea Research Foundation. 相似文献
7.
Jie FANG 《数学学报(英文版)》2007,23(9):1611-1620
An algebraic structure A is said to have the endomorphism kernel property if every congruence on A, other than the universal congruence, is the kernel of an endomorphism on A. In this paper, we consider the EKP (that is, endomorphism kernel property) for an extended Ockham algebra A. In particular, we describe the structure of the finite symmetric extended de Morgan algebras having EKP. 相似文献
8.
Sébastien Dubernet 《Archiv der Mathematik》2006,86(5):430-436
A well known “zero-two law" shows that if
is a strongly continuous one-parameter group of bounded operators on a Banach space X, and if
then
Here we discuss analogous problems for general unital representations θ of a topological group G on a unital Banach algebra A. Let 1 be the unit of G, and I the unit element of A. We show that either
or
if, moreover, θ admits “continuous division by any positive integer”, then, either
or
Our argument also gives automatic continuity results for representations of abelian Baire groups on a separable Banach algebra
and representations of compact non abelian groups on a Banach algebra which are locally bounded and satisfy
Received: 8 June 2005; revised: 13 October 2005 相似文献
9.
Let M be a four-holed sphere and Γ the mapping class group of M fixing the boundary ∂M. The group Γ acts on
which is the space of completely reducible SL (2,
-gauge equivalence classes of flat SL
-connections on M with fixed holonomy
on ∂M. Let
and
be the compact component of the real points of
. These points correspond to SU(2)-representations or SL(2,
-representations. The Γ-action preserves
and we study the topological dynamics of the Γ-action on
and show that for a dense set of holonomy
, the Γ-orbits are dense in
. We also produce a class of representations
such that the Γ-orbit of [ρ] is finite in the compact component of
, but
is dense in SL(2,
.Mathematics Subject Classiffications (2000). 57M05, 54H20, 11D99 相似文献
10.
Dietmar Vogt 《Archiv der Mathematik》2006,87(2):163-171
It is shown that for open convex
, d > 1 and a nontrivial polynomial P the space
does not have property
. If P is elliptic or homogeneous, then this holds for every open Ω. For
even
cannot occur and if it occurs for some Ω, then P must be hypoelliptic.
Received: 18 July 2005 相似文献
11.
Structure of Degenerate Block Algebras 总被引:13,自引:0,他引:13
Given a non-trivial torsion-free abelian group (A,+,Q), a field F of characteristic 0, and a non-degenerate bi-additive skew-symmetric map
: A
A
F, we define a Lie algebra
=
(A,
) over F with basis {ex | x
A/{0}} and Lie product [ex,ey] =
(x,y)ex+y. We show that
is endowed uniquely with a non-degenerate symmetric invariant bilinear form and the derivation algebra Der
of
is a complete Lie algebra. We describe the double extension D(
, T) of
by T, where T is spanned by the locally finite derivations of
, and determine the second cohomology group H2(D(
, T),F) using anti-derivations related to the form on D(
, T). Finally, we compute the second Leibniz cohomology groups HL2(
, F) and HL2(D(
, T), F).2000 Mathematics Subject Classification: 17B05, 17B30This work was supported by the NNSF of China (19971044), the Doctoral Programme Foundation of Institution of Higher Education (97005511), and the Foundation of Jiangsu Educational Committee. 相似文献
12.
Fazli Kh 《Statistical Inference for Stochastic Processes》2007,10(2):181-208
We observe a realization X
(n) of a Poisson process on the set
with intensity function
depending on the unknown real parameter
. Based on X
(n) we test simple null hypothesis
against one sided alternative
for given
. We improve the level of the well-known locally asymptotically uniformly most powerful (LAUMP) test by using the Edgeworth
type expansion for stochastic integral. We show that the improved test is second-order efficient under certain regularity
conditions.
相似文献
13.
Augusto Visintin 《Annali di Matematica Pura ed Applicata》2006,185(4):487-519
This work deals with an initial- and boundary-value problem for a quasilinear parabolic equation that includes a possibly
discontinuous hysteresis operator,
:
In particular the case of
equal to a so-called relay operator is studied. Well-posedness is proved, as well as regularity of the solution and its robustness w.r.t. perturbations of
. The large-time behaviour is studied; asymptotic stability and compactness are shown. For a time-periodic f, existence of a periodic solution is also established.
Mathematics Subject Classification (2000) 35K60, 35R35, 47J40 相似文献
14.
Chong LI Genaro LOPEZ 《数学学报(英文版)》2006,22(3):741-750
Let B (resp. K, BC,KC) denote the set of all nonempty bounded (resp. compact, bounded convex, compact convex) closed subsets of the Banach space X, endowed with the Hausdorff metric, and let G be a nonempty relatively weakly compact closed subset of X. Let B° stand for the set of all F ∈B such that the problem (F, G) is well-posed. We proved that, if X is strictly convex and Kadec, the set KC ∩ B° is a dense Gδ-subset of KC / G. Furthermore, if X is a uniformly convex Banach space, we will prove more, namely that the set B /B° (resp. K / B°, BC /B°, KC / B°) is a-porous in B (resp. K,BC, KC). Moreover, we prove that for most (in the sense of the Baire category) closed bounded subsets G of X, the set K / B° is dense and uncountable in K. 相似文献
15.
Frank Müller 《Calculus of Variations and Partial Differential Equations》2005,24(3):289-308
We study surfaces of prescribed bounded mean curvature H in a partially free boundary configuration
. If
is projectable onto and
is a cylinder surface over the x1,x2-plane, we show that also the spanned H-surface
is projectable onto this plane. Besides certain conditions on
and H, we have to suppose that
is stationary and freely stable w.r.t. the generalized area functional
, and the vector field
is assumed to be tangential on
. Consequences are uniqueness of freely stable H-surfaces and solvability of a mixed boundary problem for the nonparametric prescribed mean curvature equation.
Mathematics Subject Classification (2000): 53 A 10, 35 J 65, 35 R 35, 49 Q 05 相似文献
16.
Let Г be a G-symmetric graph admitting a nontrivial G-invariant partition
. Let Г
be the quotient graph of Г with respect to
. For each block B ∊
, the setwise stabiliser GB of B in G induces natural actions on B and on the neighbourhood Г
(B) of B in Г
. Let G(B) and G[B] be respectively the kernels of these actions. In this paper we study certain “local actions" induced by G(B) and G[B], such as the action of G[B] on B and the action of G(B) on Г
(B), and their influence on the structure of Г.
Supported by a Discovery Project Grant (DP0558677) from the Australian Research Council and a Melbourne Early Career Researcher
Grant from The University of Melbourne. 相似文献
17.
For an arbitrary set E and a given closure operator
, we want to construct a symmetric closure operator
via some – possibly infinite – iteration process. If E is finite, the corresponding symmetric closure operator .
defines a matroid. If
and
is the convex closure operator,
turns out to be the affine closure operator. Moreover, we apply the symmetrization process to closure operators induced by
visibility.
Received March 9, 2005 相似文献
18.
Denis Xavier Charles 《The Ramanujan Journal》2006,11(2):221-224
We show that the Ramanujan tau function τ(n) can be computed by a randomized algorithm that runs in time
for every O(
) assuming the Generalized Riemann Hypothesis. The same method also yields a deterministic algorithm that runs in time O(
) (without any assumptions) for every ε > 0 to compute τ(n). Previous algorithms to compute τ(n) require Ω(n) time.
Research supported in part by NSF grant CCR-9988202
2000 Mathematics Subject Classification Primary—11-04; Secondary—11Y55, 11F11 相似文献
19.
We generalize the concept of K-convexity to an n-dimensional Euclidean space. The resulting concept of
-convexity is useful in addressing production and inventory problems where there are individual product setup costs and/or
joint setup costs. We derive some basic properties of
-convex functions. We conclude the paper with some suggestions for future research.
Support from Columbia University and University of Texas at Dallas is gratefully acknowledged. Helpful comments from Qi Feng
are appreciated. 相似文献
20.
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