共查询到20条相似文献,搜索用时 31 毫秒
1.
Jan van Mill 《Topology and its Applications》1982,13(2):123-132
The reduced measure algebra is used to construct, under CH, a hereditarily Lindelöf separable K1-space X which is not a K0-space. 相似文献
2.
Let X be a locally finite simplicial complex of dimension n, n? 5, equipped with a k-fold end structure [4] and consider a piecewise linear (n + 1)-dimensional manifold M that is proper homotopy equivalent to X × R by F:M → X × R, where R is the set of real numbers. The question arises as to whether or not the manifold M can be split, i.e., written as M = N × R where N is a n-manifold and where there is a proper homotopy between F and (p1 ° F0) × id:N × R → X × R, preserving the natural (k+1)-fold end structure, where F0 is F|N and p1 is the projection X × R → X. Of particular significance is the fact that X is noncompact. When the construction of such splittings is attempted, algebraic obstructions arise, which vanish if and only if the construction can be completed. This paper develops such an obstruction theory by utilizing methods of L.C. Siebenmann and the k-fold end structures of F. Waldhausen. 相似文献
3.
Dongyang Chen 《Journal of Mathematical Analysis and Applications》2003,284(2):618-625
If X is a separable Banach space, then X∗ contains an asymptotically isometric copy of l1 if and only if there exists a quotient space of X which is asymptotically isometric to c0. If X is an infinite-dimensional normed linear space and Y is any Banach space containing an asymptotically isometric copy of c0, then L(X,Y) contains an isometric copy of l∞. If X and Y are two infinite-dimensional Banach spaces and Y contains an asymptotically isometric copy of c0, then contains a complemented asymptotically isometric copy of c0. 相似文献
4.
David Handelman 《Journal of Pure and Applied Algebra》1976,8(1):105-118
If R is any (noncommutative, von Neumann) regular ring with 2 invertible, then K1 of the free (noncommuting) R-algebra on a set X is canonically isomorphic to K1(R). If R is unit-regular, then K1(R) is just the abelianization of the group of units of R. Some examples are computed. 相似文献
5.
If X is a compact-covering image of a closed subspace of product of a σ-compact Polish space and a compact space, then Ck(X,M), the space of continuous maps of X into M with the compact-open topology, is stratifiable for any metric space M.If X is σ-compact Polish, K is compact and M metric then every point of Ck(X×K,M) has a closure-preserving local base, and hence this function space is M1. 相似文献
6.
《Topology and its Applications》1986,22(1):71-82
If P is a paracompact p-space, P×X is collectionwise normal, and Y is a closed image of X, then P×Y is collectionwise normal.If M is metric, X shrinking, and M×X is normal, then M×X is shrinking. 相似文献
7.
Jimmie D. Lawson 《Topology and its Applications》1985,21(1):73-76
The purpose of this paper is to give several different characterizations of those T0-spaces E with the property that if F:X × E → Y is separately continuous, then it is jointly continuous. One such is that the lattice 0(E) of open sets of E be a hypercontinuous lattice (i.e. the interval topology on 0(E) is Hausdorff). If E is a sober space, then E must be a quasicontinuous poset endowed with the Scott topology. 相似文献
8.
R.A. Willoughby 《Linear algebra and its applications》1977,18(1):75-94
One aspect of the inverse M-matrix problem can be posed as follows. Given a positive n × n matrix A=(aij) which has been scaled to have unit diagonal elements and off-diagonal elements which satisfy 0 < y ? aij ? x < 1, what additional element conditions will guarantee that the inverse of A exists and is an M-matrix? That is, if A?1=B=(bij), then bii> 0 and bij ? 0 for i≠j. If n=2 or x=y no further conditions are needed, but if n ? 3 and y < x, then the following is a tight sufficient condition. Define an interpolation parameter s via x2=sy+(1?s)y2; then B is an M-matrix if s?1 ? n?2. Moreover, if all off-diagonal elements of A have the value y except for aij=ajj=x when i=n?1, n and 1 ? j ? n?2, then the condition on both necessary and sufficient for B to be an M-matrix. 相似文献
9.
In 1965, Ron Douglas proved that if X is a closed subspace of an L
1-space and X is isometric to another L
1-space, then X is the range of a contractive projection on the containing L
1-space. In 1977 Arazy-Friedman showed that if a subspace X of C
1 is isometric to another C
1-space (possibly finite dimensional), then there is a contractive projection of C
1 onto X. In 1993 Kirchberg proved that if a subspace X of the predual of a von Neumann algebra M is isometric to the predual of another von Neumann algebra, then there is a contractive projection of the predual of M onto X. 相似文献
10.
N.R. Mohan 《Stochastic Processes and their Applications》1976,4(2):157-165
Let X1, X2, … be a sequence of independent and identically distributed random variables with mean zero such that the common distribution function belongs to the domain of attraction of a stable law Gα,β with 1<α<2 and β=1 or α=2. If Sn=X1+…Xn and N(ξ)=min{k:Sk>ξ}, ξ>0, then it is shown that , 0<t<1, converges weakly under the Skorohod J1-topology to a stable subordinator of index , where B1(n) depends on the norming constant for Sn. 相似文献
11.
Wolfgang Lusky 《Journal of Functional Analysis》1985,62(1):1-7
It is shown that every separable Banach space X containing a subspace isomorphic to c0 has a subspace Y with basis such that and the latter space has a shrinking basis and an unconditional FDD. Moreover, it is shown that X ⊕ C∞ has a basis if X has the bounded approximation property. 相似文献
12.
If A is an M-matrix with the property that some power of A is lower triangular, then A is lower triangular. An analogue of the Minkowski determinant theorem is proved for a subclass of the M-matrices. 相似文献
13.
We prove that the kernel of a quotient operator from an L 1-space onto a Banach space X with the Bounded Approximation Property (BAP) has the BAP. This completes earlier results of Lusky-case ? 1-and Figiel, Johnson and Pe?czyński-case X* separable. Given a Banach space X, we show that if the kernel of a quotient map from some L 1-space onto X has the BAP, then every kernel of every quotient map from any L 1-space onto X has the BAP. The dual result for L ∞-spaces also holds: if for some L ∞-space E some quotient E/X has the BAP, then for every L ∞-space E every quotient E/X has the BAP. 相似文献
14.
Liang-Xue Peng 《Topology and its Applications》2007,154(2):469-475
It is shown that the space Cp(τω) is a D-space for any ordinal number τ, where . This conclusion gives a positive answer to R.Z. Buzyakova's question. We also prove that another special example of Lindelöf space is a D-space. We discuss the D-property of spaces with point-countable weak bases. We prove that if a space X has a point-countable weak base, then X is a D-space. By this conclusion and one of T. Hoshina's conclusion, we have that if X is a countably compact space with a point-countable weak base, then X is a compact metrizable space. In the last part, we show that if a space X is a finite union of θ-refinable spaces, then X is a αD-space. 相似文献
15.
In a recent paper O. Pavlov proved the following two interesting resolvability results:
- (1)
- If a T1-space X satisfies Δ(X)>ps(X) then X is maximally resolvable.
- (2)
- If a T3-space X satisfies Δ(X)>pe(X) then X is ω-resolvable.
16.
H.R. Bennett 《Topology and its Applications》1983,15(1):7-10
A Hausdorff space each subspace of which is a paracompact p-space is an Fpp-space. A space X is a closed hereditary Baire space if each closed subspace of X is a Baire space. Using a delicate theorem of Z. Balogh it is shown that a first-countable Fpp-space that is a closed hereditary Baire space is metrizable. 相似文献
17.
Salah Mecheri Messaoud Bounkhel 《Journal of Mathematical Analysis and Applications》2003,287(1):51-60
In this paper we characterize the global minimum of an arbitrary function defined on a Banach space, in terms of a new concept of derivatives adapted for our case from a recent work due to D.J. Keckic (J. Operator Theory, submitted for publication). Using these results we establish several new characterizations of the global minimum of the map defined by Fψ(X)=‖ψ(X)‖1, where is a map defined by ψ(X)=S+φ(X) and φ:B(H)→B(H) is a linear map, S∈C1, and . Further, we apply these results to characterize the operators which are orthogonal to the range of elementary operators. 相似文献
18.
The aim of this paper is to introduce a new weak separation axiom that generalizes the separation properties between T 1 and completely Hausdorff. We call a topological space (X, τ) a T κ,ξ-space if every compact subset of X with cardinality ≦ κ is ξ-closed, where ξ is a general closure operator. We concentrate our attention mostly on two new concepts: kd-spaces and T 1/3-spaces. 相似文献
19.
Banach spaces X whose duals are isomorphic or isometric to l1(Γ) are characterized by certain classes of operators on X. It is proved that a separable, conjugate space isomorphic to a complemented subspace of an L1(S, Σ, μ) space is isomorphic to l1; a 1 space contained in a separable, conjugate space is isomorphic to a subspace of l1. 相似文献
20.
《Topology and its Applications》1988,30(2):175-181
We address the following question: “Must every wΔ-space with a Gδ-diagonal be developable?” Consistently, the answer is “no.”Example. Assume CH. There is a zero-dimensional, scattered, locally compact, wΔ-space with a Gδ-diagonal which is not developable.For normal, locally compact spaces (or slightly weaker), the answer is “yes”.Theorem. If X is ω-sCWH, locally Lindelöf, wΔ-space with a Gδ-diagonal, then X is developable. 相似文献