共查询到20条相似文献,搜索用时 653 毫秒
1.
Ren-Cang Li 《BIT Numerical Mathematics》2004,44(3):585-593
This paper establishes converses to the well-known result: for any vector
such that the sine of the angle sin(u,
)=O(), we have
,where is an eigenvalue and u is the corresponding eigenvector of a Hermitian matrix A, and * denotes complex conjugate transpose. It shows that if (
) is close to A's largest eigenvalue, then
is close to the corresponding eigenvector with an error proportional to the square root of the error in (
) as an approximation to the eigenvalue and inverse proportional to the square root of the gap between A's first two largest eigenvalues. A subspace version of such an converse is also established. Results as such may have interest in applications, such as eigenvector computations in Principal Component Analysis in image processing where eigenvectors may be computed by optimizing Rayleigh quotients with the Conjugate Gradient method. 相似文献
2.
On a Problem of the Theory of Multiply Local Formations 总被引:1,自引:0,他引:1
We describe the -closed n-multiply local formations
such that the lattice of all -closed n-multiply local formations between
and
is Boolean. 相似文献
3.
We prove that if a group G is residually
, then for every
-subgroup of the group G, the set of -roots from this subgroup is a -separable
-subgroup. 相似文献
4.
P. Cubiotti 《Journal of Optimization Theory and Applications》1997,92(3):477-495
Given a nonempty set
and two multifunctions
, we consider the following generalized quasi-variational inequality problem associated with X, : Find
such that
. We prove several existence results in which the multifunction is not supposed to have any continuity property. Among others, we extend the results obtained in Ref. 1 for the case (x(X. 相似文献
5.
In this paper, we consider several constructions which from a given B-product *
B
lead to another one
We shall be interested in finding what algebraic properties of the ring
are shared also by the ring
. In particular, for some constructions the rings R
B and
will be isomorphic and therefore have the same algebraic properties. 相似文献
6.
Let
be an abstract class (closed under isomorpic copies) of left R-modules. In the first part of the paper some sufficient conditions under which
is a precover class are given. The next section studies the
-precovers which are
-covers. In the final part the results obtained are applied to the hereditary torsion theories on the category on left R-modules. Especially, several sufficient conditions for the existence of -torsionfree and -torsionfree -injective covers are presented. 相似文献
7.
Marian Nowak 《Czechoslovak Mathematical Journal》2000,50(2):401-414
Let
be a real Banach space and let E be an ideal of L
0 over a -finite measure space (, , ). Let (X) be the space of all strongly -measurable functions f: X such that the scalar function
, defined by
, belongs to E. The paper deals with strong topologies on E(X). In particular, the strong topology
the order continuous dual of E(X)) is examined. We generalize earlier results of [PC] and [FPS] concerning the strong topologies. 相似文献
8.
We show that if two Riemannian metrics
and g are pointwiseprojectively equivalent and the Ricci curvatures satisfy
Ric, then the projective equivalence is trivialprovided that g is complete. In this case,
is parallel with respect to g and the Riemann curvatures of g and
are equal.The Ricci curvature condition can be weakened when the manifold iscompact. This rigidity theorem actually holds for more general geometricstructures, such as Finsler metrics and sprays. In this paper, we willalso discuss several examples and show that the completeness of g cannot be dropped. 相似文献
9.
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
10.
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
11.
In this study, we discuss one type of variational inequality problem with a fuzzy convex cone
, denoted by VI(
, f). Different classes of fuzzy convex cones which are considered in different context of the problems will be discussed. According to the existence theorem, an approach derived from the concepts of multiple objective mathematical programming problems for solving the VI(
, f) is proposed. An algorithm is developed to find its fuzzy optimal solution set with complexity analysis. 相似文献
12.
Considering mixed-norm sequence spaces lp,q, p, q 1, C. N. Kellogg proved the following theorem: if 1 < p 2 then
lp,2 and lp,2
, where 1/p + 1/p = 1. This result extends the Hausdorff-Young Theorem.We introduce here multiple mixed-norm sequence spaces
, examine their properties and characterize the multipliers of spaces of the form lp,[s;n],q, with the index s repeated n times. By an interpolation-type argument we prove that
(l,[2;n],2, lp,[1;n],1) for 1 < p 2. Using these results we obtain a further generalization of the Hausdorff-Young Theorem: if 1 < p 2 then
lp,[2;n] and lp,[2;n]
for each n = 0, 1, 2, ¨. The spaces lp,[2;n] decrease and lp,[2;n] increase properly with n for 1 < p < 2 and 1/p + 1/p = 1. We also extend a theorem of J. H. Hedlund on multiplers of Hardy spaces
and deduce other results. 相似文献
13.
The multidimensional Sparr interpolation method is implemented in the Besov spaces
and the Lizorkin--Triebel spaces
. It is shown that this results in Besov spaces of type
. An interpolation theorem for Besov spaces using weak conditions of the form
is formulated. 相似文献
14.
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
15.
Let
be the j-fold iterated function of
. Let
and > 0 be fixed, Q be a prime, and let N
k(Q|x) denote the number of those nx for which Q
. We give the asymptotics of N
k(Q|x) in the range
. 相似文献
16.
We prove four theorems about groups with a dihedral (or cyclic) image containing a difference set. For the first two, suppose G, a group of order 2p
with p an odd prime, contains a nontrivial (v, k, ) difference set D with order n = k – prime to p and self-conjugate modulo p. If G has an image of order p, then 0 2a +
2
for a unique choice of = ±1, and for a = (k –
)/2p. If G has an image of order 2p, then
and
(
– 1)/(
– 1). There are further constraints on n, a and . We give examples in which these theorems imply no difference set can exist in a group of a specified order, including filling in some entries in Smith's extension to nonabelian groups of Lander's tables. A similar theorem covers the case when p|n. Finally, we show that if G contains a nontrivial (v, k, ) difference set D and has a dihedral image D
2m
with either (n, m) = 1 or m = p
t
for p an odd prime dividing n, then one of the C
2 intersection numbers of D is divisible by m. Again, this gives some non-existence results. 相似文献
17.
On the Harris Recurrence of Iterated Random Lipschitz Functions and Related Convergence Rate Results 总被引:1,自引:0,他引:1
Gerold Alsmeyer 《Journal of Theoretical Probability》2003,16(1):217-247
A result by Elton(6) states that an iterated function system
of i.i.d. random Lipschitz maps F
1,F
2,... on a locally compact, complete separable metric space
converges weakly to its unique stationary distribution if the pertinent Liapunov exponent is a.s. negative and
for some
. Diaconis and Freedman(5) showed the convergence rate be geometric in the Prokhorov metric if
for some p>0, where L
1 denotes the Lipschitz constant of F
1. The same and also polynomial rates have been recently obtained in Alsmeyer and Fuh(1) by different methods. In this article, necessary and sufficient conditions are given for the positive Harris recurrence of (M
n
)
n0 on some absorbing subset
. If
and the support of has nonempty interior, we further show that the same respective moment conditions ensuring the weak convergence rate results mentioned above now lead to polynomial, respectively geometric rate results for the convergence to in total variation or f-norm
f
, f(x)=1+d(x,x
0)
for some (0,p]. The results are applied to various examples that have been discussed in the literature, including the Beta walk, multivariate ARMA models and matrix recursions. 相似文献
18.
We introduce the notion of hyper-self-duality for Bose-Mesner algebras as a strengthening of formal self-duality. Let
denote a Bose-Mesner algebra on a finite nonempty set X. Fix p X, and let
and
denote respectively the dual Bose-Mesner algebra and the Terwilliger algebra of
with respect to p. By a hyper-duality of
, we mean an automorphism of
such that
for all
; and
is a duality of
.
is said to be hyper-self-dual whenever there exists a hyper-duality of
. We say that
is strongly hyper-self-dual whenever there exists a hyper-duality of
which can be expressed as conjugation by an invertible element of
. We show that Bose-Mesner algebras which support a spin model are strongly hyper-self-dual, and we characterize strong hyper-self-duality via the module structure of the associated Terwilliger algebra. 相似文献
19.
V. V. Kornienko 《Mathematical Notes》2000,68(5-6):576-587
We study the distribution in the complex plane
of the spectrum of the operator
, generated by the closure in
of the operation
originally defined on smooth functions
with values in a Hilbert space
satisfying the Dirichlet conditions
. Here
and A is a model operator acting in
. Criterial conditions on the parameter
for the eigenfunctions of the operator
to form a complete and minimal system as well as a Riesz basis in the Hilbert space H are given. 相似文献
20.
P. M. Fuchs 《BIT Numerical Mathematics》1989,29(2):295-310
In this paper the general classV of spline-collocation methods presented by Mülthei is investigated. The methods ofV approximate solutions of first order initial value problems. ClassV contains as subclass the methods of so-called multivalue type, and in particular contains the generalized singly-implicit methods treated by Butcher.Any multivalue type representativeU V yields a matrix valued function corresponding toU, which characterizes the region of absolute stability ofU. If a sequence (U()) of multivalue type representatives ofV tending to some singlevalue type representative
V is considered, it can easily be seen by the structure of , that the sequence of the greatest eigenvalues of the (.,) tends to the stability function
corresponding to
. This fact allows one to construct one-parameter families of A-stable methods of multivalue type. 相似文献