共查询到20条相似文献,搜索用时 31 毫秒
1.
We prove that ifT is a strictly singular one-to-one operator defined on an infinite dimensional Banach spaceX, then for every infinite dimensional subspaceY ofX there exists an infinite dimensional subspaceZ ofX such thatZ∩Y is infinite dimensional,Z contains orbits ofT of every finite length and the restriction ofT toZ is a compact operator.
The research was partially supported by NSF. 相似文献
2.
It is proved that ifX=c
0 orm and ifY andZ are subspaces ofX withX/Y andX/Z non-reflexive, then any isomorphism ofY ontoZ has an extension to an automorphism ofX. A dual result is obtained forX=l
1.
This research was partially supported by NSF-GP-8964. 相似文献
3.
LetX be a connected graph with bounded valency and at least one thick end. We show that the existence of certain subgroups of the automorphism group ofX always implies thatX has infinite Hadwiger number. 相似文献
4.
Norbert Seifter 《Combinatorica》1984,4(4):351-356
LexX be anm-connected infinite graph without subgraphs homeomorphic toKm, n, for somen, and let α be an automorphism ofX with at least one cycle of infinite length. We characterize the structure of α and use this characterization to extend a
known result about orientation-preserving automorphisms of finite plane graphs to infinite plane graphs. In the last section
we investigate the action of α on the ends ofX and show that α fixes at most two ends (Theorem 3.2). 相似文献
5.
Francesco de Giovanni Alessio Russo Giovanni Vincenzi 《Mediterranean Journal of Mathematics》2007,4(1):65-71
A subgroup X of a group G is called pronormal-by-finite if there exists a pronormal subgroup Y of G such that Y ≤ X and |X : Y| is finite. The structure of (generalized) soluble groups in which all subgroups are pronormal-by-finite is investigated.
Among other results, it is proved in particular that a finitely generated soluble group with such property is central-by-finite,
provided that it has no infinite dihedral sections. 相似文献
6.
Some results on the residual life at random time 总被引:2,自引:0,他引:2
In this paper, we consider the residual life at random time, i.e.X
Y
=X−Y\X>Y, whereX andY are non-negative random variables. We establish a number of stochastic comparison properties forX
Y
under various assumptions ofX andY. Under the assumption thatY has decreasing reverse hazard rate (DRHR), we show that ifX is in any one of the classes IFR, DFR, DMRL or IMRL thenX
Y
is in the same class asX. We also obtain some useful bounds for the distribution and the moment ofX
Y
. Because the idle time in classicalGI/G/1 queuing system can be regarded as the residual life at random time, the results obtained in this paper have applications
in the study of such system.
This work is supported by the National Natural Science Foundation of China. 相似文献
7.
Wilfried Imrich 《Israel Journal of Mathematics》1972,11(3):258-264
A graphX is called a graphical regular representation (GRR) of a groupG if the automorphism group ofX is regular and isomorphic toG. Watkins and Nowitz have shown that the direct productG×H of two finite groupsG andH has aGRR if both factors have aGRR and if at least one factor is different from the cyclic group of order two. We give a new proof of this result, thereby removing
the restriction to finite groups. We further show that the complementX′ of a finite or infinite graphX is prime with respect to cartesian multiplication ifX is composite and not one of six exceptional graphs. 相似文献
8.
Chris D. Godsil Wilfried Imrich Norbert Seifter Mark E. Watkins Wolfgang Woess 《Graphs and Combinatorics》1989,5(1):333-338
LetX be a connected locally finite graph with vertex-transitive automorphism group. IfX has polynomial growth then the set of all bounded automorphisms of finite order is a locally finite, periodic normal subgroup ofAUT(X) and the action ofAUT(X) onV(X) is imprimitive ifX is not finite. IfX has infinitely many ends, the group of bounded automorphisms itself is locally finite and periodic. 相似文献
9.
Procopis Psaltis 《Israel Journal of Mathematics》2008,163(1):345-367
A group G is called unsplittable if Hom(G, ℤ) = 0 and this group is not a non-trivial amalgam. Let X be a tree with a countable number of edges incident at each vertex and G be its automorphism group. In this paper we prove that the vertex stabilizers are unsplittable groups.
Bass and Lubotzky proved (see [3]) that for certain locally finite trees X, the automorphism group determines the tree X (that is, knowing the automorphism group we can “construct” the tree X). We generalize this Theorem of Bass and Lubotzky, using the above result. In particular we show that the Theorem holds even
for trees which are not locally finite.
Moreover, we prove that the permutation group of an infinite countable set is unsplittable and the infinite (or finite) cartesian
product of unsplittable groups is an unsplittable group as well.
This research was supported by the European Social Fund and National resources-EPEAEK II grant Pythagoras 70/3/7298. 相似文献
10.
A Banach spaceX is non-quasi-reflexive (i.e. dimX **/X=∞) if and only if it contains a basic sequence spanning a non-quasi-reflexive subspace. In fact, this basic sequence can be chosen to be non-k-boundedly complete for allk. A basic sequence which is non-k-shrinking for allk exists inX if and only ifX * contains a norming subspace of infinite codimension. This need not occur even ifX is non-quasi-reflexive. Every norming subspace ofX * has finite codimension if and only if for every normingM inX *, everyM-closedY inX,M∩Y T is norming overX/Y. This solves a problem due to Schäffer [19]. 相似文献
11.
Dominique Arlettaz 《manuscripta mathematica》1989,64(4):431-443
The classical extension problem is to determine whether or not a given mapg:AY, defined on a given subspaceA of a spaceX, has an extensionXY. The present paper examines this question in the special case where thek-invariants ofY are cohomology classes of finite order (for instance ifY is an infinite loop space). 相似文献
12.
Gerhard Behrendt 《Monatshefte für Mathematik》1987,103(2):77-83
We consider a setX with a finite totally ordered setE of equivalence relations onX. We describe the automorphism group of this system, that is, the group of all those permutations ofX that leave each relation inE invariant. 相似文献
13.
Michael Falk 《Journal of multivariate analysis》1998,67(2):306-317
The comedianCOM(X, Y) of random variablesX,Yis a median based robust alternative to the covariance ofXofY. For the bivariate normal case it is known thatCOM(X, Y), standardized by the median absolute deviations ofXandY, is a symmetric, strictly increasing and continuous function of the correlation coefficientρwith range [−1, 1] and can therefore serve as a robust alternative toρ. We show that this result, which is not true in general, extends to elliptical distributions even in the case where moments ofX,Ydo not exist. 相似文献
14.
The first part of the paper is concerned with conditions under which the inequality dim X × Y ≤ dim X + dim Y and similar inequalities for infinite topological products hold. The second part contains examples of spaces such that the
sums of their dimensions are smaller than the dimensions of their products.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 34, General
Topology, 2005. 相似文献
15.
S. J. Dilworth 《Israel Journal of Mathematics》1985,52(1-2):15-27
Suppose that 1<p≦2, 2≦q<∞. The formal identity operatorI:l
p→l
qfactorizes through any given non-compact operator from ap-smooth Banach space into aq-convex Banach space. It follows that ifX is a 2-convex space andY is an infinite dimensional subspace ofX which is isomorphic to a Hilbert space, thenY contains an isomorphic copy ofl
2 which is complemented inX. 相似文献
16.
Jacques Stern 《Israel Journal of Mathematics》1976,24(1):1-15
LetX be a Banach space. A Banach spaceY is an envelope ofX if (1)Y is finitely representable inX; (2) any Banach spaceZ finitely representable inX and of density character not exceeding that ofY is isometric to a subspace ofY. Lindenstrauss and Pelczynski have asked whether any separable Banach space has a separable envelope. We give a negative
answer to this question by showing the existence of a Banach space isomorphic tol
2, which has no separable envelope. A weaker positive result holds: any separable Banach space has an envelope of density character
≦ℵ1 (assuming the continuum hypothesis). 相似文献
17.
Gun-Marie Lövblom 《Israel Journal of Mathematics》1986,56(2):143-159
We characterize the isometries fromC(X) intoC(Y) whereX andY are compact metric spaces. We give necessary and sufficient conditions on an isometry from a subset ofC(X) intoC(Y) to have an extension to the whole space. It is also shown that an almost isometry from the unit ball ofC(X) into the unit ball ofC(Y) is near to an isometry. 相似文献
18.
Summary Precise conditions are obtained for the packing measure of an arbitrary subordinator to be zero, positive and finite, or infinite. It develops that the packing measure problem for a subordinatorX(t) is equivalent to the upper local growth problem forY(t)=min (Y
1
(t), Y
2
(t)), whereY
1 andY
2 are independent copies ofX. A finite and positive packing measure is possible for subordinators close to Cauchy; for such a subordinator there is non-random concave upwards function that exactly describes the upper local growth ofY (although, as is well known, there is no such function for the subordinatorX itself).Research supported in part by NSF under contracts (1) DMS 87-01866, and (2) DMS 87-01212 相似文献
19.
Antonio Kirson 《Annali dell'Universita di Ferrara》2010,56(2):327-333
An automorphism σ of a projective variety X is said to be wild if σ(Y) ≠ Y for every non-empty subvariety
Y \subsetneq X{Y \subsetneq X} . In [1] Z. Reichstein, D. Rogalski, and J.J. Zhang conjectured that if X is an irreducible projective variety admitting a wild automorphism then X is an abelian variety, and proved this conjecture for dim(X) ≤ 2. As a step toward answering this conjecture in higher dimensions we prove a structure theorem for projective varieties
of Kodaira dimension 0 admitting wild automorphisms. This essentially reduces the Kodaira dimension 0 case to a study of Calabi-Yau
varieties, which we also investigate. In support of this conjecture, we show that there are no wild automorphisms of certain
Calabi-Yau varieties. 相似文献
20.
Shie-Shien Yang 《Annals of the Institute of Statistical Mathematics》1981,33(1):463-470
Summary Let (X
1,Y
1), (X
2,Y
2),…, (X
n,Y
n) be i.i.d. as (X, Y). TheY-variate paired with therth orderedX-variateX
rn is denoted byY
rn and terms the concomitant of therth order statistic. Statistics of the form
are considered. The asymptotic normality ofT
n is established. The asymptotic results are used to test univariate and bivariate normality, to test independence and linearity
ofX andY, and to estimate regression coefficient based on complete and censored samples. 相似文献