共查询到20条相似文献,搜索用时 15 毫秒
1.
In contrast to the situation in 3, where a 2-sphere with double tangent balls at each point must be tamely embedded in 3, there exist wild (n?1)-spheres in n for n>3 with this same geometric property. However, if the sphere Σ is tame moduio a subset X that lies in a polyhedron P that is tame in Σ, the dimension of P is less than n?2, n>4, and Σ has double tangent balls over X, then Σ must be tame in n. Also if the tangent balls extend over P and are pairwise congruent, the dimensional restriction on P can be dropped. Examples are given to support the necessity of the hypotheses of the included theorems. 相似文献
2.
The purpose of this paper is to characterize and interrelate various degrees of stability and semipositivity for real square matrices having nonpositive off-diagonal entries. The major classes considered are the sets of diagonally stable, stable, and semipositive matrices, denoted respectively by , , and . The conditions defining these classes are weakened, and the resulting classes are examined. Their relationship to the classes of real matrices and 0, whose off-diagonal entries are nonpositive and whose principal minors are respectively all positive and all nonnegative, is also included. 相似文献
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Sadayoshi Kojima 《Topology and its Applications》1983,16(1):43-60
We present the failure of Whitney's lemma in dimension 4 from the homotopical and topological viewpoints. Those are detected by Massey products. The invariants for the examples represented by framed links are computed in terms of Milnor's -invariants. 相似文献
6.
Robert Gold 《Journal of Number Theory》1976,8(4):420-423
Let ((?m)) and ((3m)) be a pair of quadratic fields, m > 0, and let λ?, μ?; λ+, μ+ be the respective Iwasawa invariants of the basic 3-extensions of these fields. A generalization of a result of Scholz shows that λ? ≥ λ+ and if μ? = 0, then μ+ = 0. 相似文献
7.
Dan Yasaki 《Selecta Mathematica, New Series》2006,12(3-4):541-564
Let X = Γ \G/ K be an arithmetic quotient of a symmetric space of non-compact type. In the case that G has
-rank 1, we construct Γ-equivariant deformation retractions of D = G/K onto a set D0. We prove that D0 is a spine, having dimension equal to the virtual cohomological dimension of Γ. In fact, there is a (k − 1)-parameter family of such deformation retractions, where k is the number of Γ -conjugacy classes of rational parabolic subgroups of G. The construction of the spine also gives a way to construct an exact fundamental domain for Γ. 相似文献
8.
J.J. Dijkstra 《Topology and its Applications》1985,19(1):13-28
In their paper on pseudo-boundaries and pseudo-interiors R. Geoghegan and R.R. Summerhill construct k-dimensional pseudo-boundaries in n, where they used West's notion of a pseudo-boundary, rather than Toruńczyk's. In this paper we construct pseudo-boundaries in the sense of Toruńczyk (skeletoids) in n and use this result to find k-dimensional skeletoids in the Hilbert cube. 相似文献
9.
M. A. Natsheh 《Periodica Mathematica Hungarica》1993,26(1):7-14
Leth be a cyclic action of periodn onM, whereM is eitherS
1×K, K is the Klein bottle or on
, the twisted Klein bottle bundle overS
1, such that there is a fiberingq:MS
1 with fiber a Klein bottleK or a torusT with respect to which the action is fiber preserving. We classify all such actions and show that they might be distinguished by their fixed points or by their orbit spaces. 相似文献
10.
Ulrich Höhle 《Fuzzy Sets and Systems》1984,13(1):39-63
Considering complete Boolean algebras as sets of truth values a new concept of compactness—so-called probabilistic compactness — is introduced to -fuzzy topological spaces. The aim of this paper is to show that the most important theorems of the theory of ordinary compact spaces remain true; e.g. probabilistic compactness is preserved under projective limits, every probabilistic compact space has an unique -fuzzy uniformity being compatible with the underlying -fuzzy topology, etc. Finally using the selection theorem due to Kuratowski and Ryll-Nardzewski a non-trivial example of a probabilistic compact space is given. 相似文献
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Igor Frenkel Mikhail Khovanov Catharina Stroppel 《Selecta Mathematica, New Series》2006,12(3-4):379-431
The purpose of this paper is to study categorifications of tensor products of finite-dimensional modules for the quantum group
for
. The main categorification is obtained using certain Harish-Chandra bimodules for the complex Lie algebra
. For the special case of simple modules we naturally deduce a categorification via modules over the cohomology ring of certain
flag varieties. Further geometric categorifications and the relation to Steinberg varieties are discussed.We also give a categorical
version of the quantised Schur–Weyl duality and an interpretation of the (dual) canonical bases and the (dual) standard bases
in terms of projective, tilting, standard and simple Harish-Chandra bimodules. 相似文献
13.
Ernst Kleinert 《Journal of Number Theory》1981,13(4):541-561
The unit of the group rings of the dihedral groups D2m (m square free odd) over the rational integer ring are represented by matrices over algebraic number fields. Thereby their multiplicative structure is revealed. 相似文献
14.
Joel Anderson 《Journal of Functional Analysis》1979,31(2):195-217
Three main results are obtained: (1) If is an atomic maximal Abelian subalgebra of (), is the projection of () onto and h is a complex homomorphism on , then h ° is a pure state on (). (2) If {Pn} is a sequence of mutually orthogonal projections with rank(Pn) = n and ∑ Pn = I, is the projection of () onto {Pn}″ given by P(T)=∑tracen(T)Pn and h is a homomorphism on {Pn}″ such that h(Pn) = 0 for all n then h ° induces a type II∞ factor representation of the Calkin algebra. (3) If is a nonatomic maximal Abelian subalgebra of () then there is an atomic maximal Abelian subalgebra of () and a large family {Φα} of 1-homomorphisms from onto such that for each α, Φα ° is an extreme point in the set of projections from () onto . (Here denotes the projection of () onto .) 相似文献
15.
Alain Escassut 《Journal of Number Theory》1983,16(3):395-402
Let (K, ∥ · ∥) be a valued transcendence degree 1 extension of p. An element x ∈ K transcendental over p is said to have order ≤a (a > 0) if there exists Cx > 0 such that every polynomial P(X) ∈ p [X] satisfies when ∥ · ∥ is the Gauss norm on p[X]. No x ∈ p can have order ≤α if α < 1 but we construct some x ∈ p with order ≤ 1. Furthermore, we prove order ≤α is stable by algebraic extension. 相似文献
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Ulrich Höhle 《Journal of Mathematical Analysis and Applications》1985,108(1):113-150
Considering complete Boolean algebras as sets of truth values the structure of a fuzzy topological group, fuzzy topological ring, etc., is specified. The probabilistic completion of ordinary topological algebraic structures shows the applicability of these concepts to the theory of stochastic processes, e.g., a new definition of the stochastic integral is presented in Section 5. 相似文献
18.
Július Korbaš 《manuscripta mathematica》1994,82(1):67-70
We derive in a simple way some higher estimates of the number of every-where linearly independent cross-sections for even
multiples of real vector bundles, and, more generally, for a certain class of homomorphism bundles, supposing that there exists
at least one nowhere vanishing cross-section. 相似文献
19.
Fons van Engelen 《Topology and its Applications》1984,17(3):275-285
Let X be separable, completely metrizable, and dense in itself. We show that if X admits a triple (D1, D2, h) of two countable dense subsets D1 and D2 and a homeomorphism h: X?D1 → X?D2, satisfying some special properties, then there is a rigid subspace A of X such that A is homeomorphic to X?A = h[A]; for , such atriple is shown to exist. 相似文献
20.
Katsuro Sakai 《Topology and its Applications》1984,18(1):69-79
We give a characterization of manifolds modeled on or , where Q is the Hilbert cube, and elementary short proofs of the Open Embedding Theorem for these manifolds and the following theorem generalizing the Stability Theorem: Each fine homotopy equivalence between these manifolds is a near homeomorphism. Moreover we establish the Open Embedding Approximation Theorem. 相似文献