共查询到20条相似文献,搜索用时 23 毫秒
1.
V. I. Zvonilov S. Yu. Orevkov 《Proceedings of the Steklov Institute of Mathematics》2017,298(1):118-128
For a closed oriented surface Σ we define its degenerations into singular surfaces that are locally homeomorphic to wedges of disks. Let XΣ,n be the set of isomorphism classes of orientation-preserving n-fold branched coverings Σ → S 2 of the two-dimensional sphere. We complete XΣ,n with the isomorphism classes of mappings that cover the sphere by the degenerations of Σ. In the case Σ = S 2, the topology that we define on the obtained completion \({\overline X _{\Sigma ,n}}\) coincides on \({X_{{s^2},n}}\) with the topology induced by the space of coefficients of rational functions P/Q, where P and Q are homogeneous polynomials of degree n on ?P1 ≌ S 2. We prove that \({\overline X _{\Sigma ,n}}\) coincides with the Diaz–Edidin–Natanzon–Turaev compactification of the Hurwitz space H(Σ, n) ? X Σ,n consisting of isomorphism classes of branched coverings with all critical values being simple. 相似文献
2.
Let X be a real normed space and let f: ? → X be a continuous mapping. Let T f (t 0) be the contingent of the graph G(f) at a point (t 0, f(t 0)) and let S + ? (0,∞) × X be the “right” unit hemisphere centered at (0, 0 X ). We show that
相似文献
- 1.If dimX < ∞ and the dilation D(f, t 0) of f at t 0 is finite then T f (t 0) ∩ S + is compact and connected. The result holds for \(T_f (t_0 ) \cap \overline {S^ + } \) even with infinite dilation in the case f: [0,∞) → X.
- 2.If dimX = ∞, then, given any compact set F ? S +, there exists a Lipschitz mapping f: ? → X such that T f (t 0) ∩ S + = F.
- 3.But if a closed set F ? S + has cardinality greater than that of the continuum then the relation T f (t 0) ∩ S + = F does not hold for any Lipschitz f: ? → X.
3.
Let T X denote the full transformation semigroup on a set X. For an equivalence E on X, let Then T ?(X) is exactly the semigroup of mappings on the topological space X for which the collection of all E-classes is a basis. In this paper, we discuss regularity of elements and Green’s relations for T ?(X).
相似文献
$T_{\exists}(X)=\{\alpha\in T_X:\forall x,y\in X,(x\alpha,y\alpha)\in E\Rightarrow(x,y)\in E\}.$
4.
A class of circuits of functional elements over the standard basis of the conjunction, disjunction, and negation elements is considered. For each circuit Σ in this class, its depth D(Σ) and dimension R(Σ) equal to the minimum dimension of the Boolean cube allowing isomorphic embedding Σ are defined. It is established that for n = 1, 2,… and an arbitrary Boolean function f of n variables there exists a circuit Σf for implementing this function such that R(Σf) ? n ? log2 log2n + O(1) and D(Σf) ? 2n ? 2 log2 log2n + O(1). It is proved that for n = 1, 2,… almost all functions of n variables allow implementation by circuits of the considered type, whose depth and dimension differ from the minimum values of these parameters (for all equivalent circuits) by no more than a constant and asymptotically no more than by a factor of 2, respectively. 相似文献
5.
We introduce the notion of a (stable) dimension scale d-sc(X) of a space X, where d is a dimension invariant. A bicompactum X is called dimensionally unified if dim F = dimG F for every closed F ? X and for an arbitrary abelian group G. We prove that there exist dimensionally unified bicompacta with every given stable scale dim-sc. 相似文献
6.
A. Nekvinda 《Acta Mathematica Hungarica》2016,148(1):43-55
Given c > 0 a planar Cantor set X with a dim H (X) < 2 is constructed such that each c-monotone subspace of X has a smaller Hausdorff dimension than X. 相似文献
7.
Let X and Y be completely regular spaces and E and F be Hausdorff topological vector spaces. We call a linear map T from a subspace of C(X, E) into C(Y, F) a Banach–Stone map if it has the form T f (y) = S y (f (h(y))) for a family of linear operators S y : E → F, \({y \in Y}\) , and a function h: Y → X. In this paper, we consider maps having the property: where Z(f) = {f = 0}. We characterize linear bijections with property (Z) between spaces of continuous functions, respectively, spaces of differentiable functions (including C ∞), as Banach–Stone maps. In particular, we confirm a conjecture of Ercan and Önal: Suppose that X and Y are realcompact spaces and E and F are Hausdorff topological vector lattices (respectively, C *-algebras). Let T: C(X, E) → C(Y, F) be a vector lattice isomorphism (respectively, *-algebra isomorphism) such thatThen X is homeomorphic to Y and E is lattice isomorphic (respectively, C *-isomorphic) to F. Some results concerning the continuity of T are also obtained.
相似文献
$\bigcap^{k}_{i=1}Z(f_{i}) \neq\emptyset \iff \bigcap^{k}_{i=1}Z(Tf_{i})\neq\emptyset , \quad({\rm Z}) $
$ Z(f) \neq\emptyset\iff Z(Tf) \neq\emptyset. $
8.
K. V. Storozhuk 《Siberian Mathematical Journal》2010,51(2):330-337
Let T t : X → X be a C 0-semigroup with generator A. We prove that if the abscissa of uniform boundedness of the resolvent s 0(A) is greater than zero then for each nondecreasing function h(s): ?+ → R + there are x′ ∈ X′ and x ∈ X satisfying ∫ 0 ∞ h(|〈x′, T x x〉|)dt = ∞. If i? ∩ Sp(A) ≠ Ø then such x may be taken in D(A ∞). 相似文献
9.
Dumitru Popa 《Proceedings Mathematical Sciences》2007,117(1):13-30
We prove that if X, Y are Banach spaces, Ω a compact Hausdorff space and U:C(Ω, X) → Y is a bounded linear operator, and if U is a Dunford-Pettis operator the range of the representing measure G(Σ) ? DP(X, Y) is an uniformly Dunford-Pettis family of operators and ∥G∥ is continuous at Ø. As applications of this result we give necessary and/or sufficient conditions that some bounded linear operators on the space C([0, 1], X) with values in c 0 or l p, (1 ≤ p < ∞) be Dunford-Pettis and/or compact operators, in which, Khinchin’s inequality plays an important role. 相似文献
10.
Let P be a subgroup of a Sylow subgroup of a finite group G. If P is a Sylow subgroup of some normal subgroup of G then P is called normally embedded in G. We establish tests for a finite group G to be p-supersoluble provided that every maximal subgroup of a Sylow p-subgroup of X is normally embedded in G. We study the cases when X is a normal subgroup of G, X = Op',p(H), and X = F*(H) where H is a normal subgroup of G. 相似文献
11.
Let (X , x 0) be a pointed smooth proper variety defined over an algebraically closed field. The Albanese morphism for (X , x 0) produces a homomorphism from the abelianization of the F-divided fundamental group scheme of X to the F-divided fundamental group of the Albanese variety of X. We prove that this homomorphism is surjective with finite kernel. The kernel is also described. 相似文献
12.
Yan-Kui Song 《Czechoslovak Mathematical Journal》2008,58(3):823-831
In this paper, we prove the following statements(1) There exists a Hausdorff Lindelöf space X such that the Alexandroff duplicate A(X) of X is not discretely absolutely star-Lindelöf.(2) If X is a regular Lindelöf space, then A(X) is discretely absolutely star-Lindelöf.(3) If X is a normal discretely star-Lindelöf space with e(X) < ω 1, then A(X) is discretely absolutely star-Lindelöf. 相似文献
13.
Ken-Ichi Yoshikawa 《Mathematische Annalen》2007,337(1):61-89
Let π: X → S be a holomorphic map from a compact Kähler manifold (X,g X ) to a compact Riemann surface S. Let Σπ be the critical locus of π and let Δ = π(Σπ) be the discriminant locus. Let (ξ, h ξ) be a holomorphic Hermitian vector bundle on X. We determine the singularity of the Quillen metric on det Rπ*ξ near Δ with respect to g X | TX/S and h ξ. 相似文献
14.
15.
G. K. Agrafiotis M. Z. Tsoukalas 《The Journal of the Operational Research Society》1995,46(10):1269-1280
In this paper a class of correlated cumulative processes, B s (t) = ∑N(t)i=1 H s (X i )X i , is studied with excess level increments X i ?s, where {N(t), t ?0} is the counting process generated by the renewal sequence T n , T n and X n are correlated for given n, H s (t) is the Heaviside function and s?0 is a given constant. Several useful results, for the distributions of B s (t), and that of the number of excess (non-excess) increments on (0, t) and the corresponding means, are derived. First passage time problems are also discussed and various asymptotic properties of the processes are obtained. Transform results, by applying a flexible form for the joint distribution of correlated pairs (T n , X n ) are derived and inverted. The case of non-excess level increments, X i < s, is also considered. Finally, applications to known stochastic shock and pro-rata warranty models are given. 相似文献
16.
BAI Peng Department of Statistics University of Yunnan Kunming China 《中国科学A辑(英文版)》2005,48(12):1597-1608
For a GMANOVA-MANOVA model with normal error: Y = XB1Z1 T B2Z2 T E, E- Nq×n(0, In (?) ∑), the present paper is devoted to the study of distribution of MLE, ∑, of covariance matrix ∑. The main results obtained are stated as follows: (1) When rk(Z) -rk(Z2) ≥ q-rk(X), the exact distribution of ∑ is derived, where z = (Z1,Z2), rk(A) denotes the rank of matrix A. (2) The exact distribution of |∑| is gained. (3) It is proved that ntr{[S-1 - ∑-1XM(MTXT∑-1XM)-1MTXT∑-1]∑}has X2(q_rk(x))(n-rk(z2)) distribution, where M is the matrix whose columns are the standardized orthogonal eigenvectors corresponding to the nonzero eigenvalues of XT∑-1X. 相似文献
17.
Let X be a Banach space with a weak uniform normal structure and C a non–empty convexweakly compact subset of X. Under some suitable restriction, we prove that every asymptoticallyregular semigroup T = {T(t) : t ∈¸ S} of selfmappings on C satisfying
has a common fixed point, where WCS(X) is the weakly convergent sequence coefficient of X, and\({\left| {{\left\| {T(t)} \right\|}} \right|}\) is the exact Lipschitz constant of T(t). 相似文献
${\mathop {\lim \inf }\limits_{S \mathrel\backepsilon t \to \infty } }{\left| {{\left\| {T(t)} \right\|}} \right|} < {\text{WCS}}(X)$
18.
Bernard A. Anderson 《Archive for Mathematical Logic》2011,50(3-4):361-365
A real X is defined to be relatively c.e. if there is a real Y such that X is c.e.(Y) and \({X \not\leq_T Y}\). A real X is relatively simple and above if there is a real Y < T X such that X is c.e.(Y) and there is no infinite set \({Z \subseteq \overline{X}}\) such that Z is c.e.(Y). We prove that every nonempty \({\Pi^0_1}\) class contains a member which is not relatively c.e. and that every 1-generic real is relatively simple and above. 相似文献
19.
We consider the random difference equations S = d (X + S)Y and T = d X + TY, where = d denotes equality in distribution, X and Y are two nonnegative random variables, and S and T on the right-hand side are independent of (X, Y). Under the assumptions that X follows a subexponential distribution with a nonzero lower Karamata index, that Y takes values in [0, 1] and is not degenerate at 0 or 1, and that (X, Y) fulfills a certain dependence structure via the conditional tail probability of X given Y, we derive some asymptotic formulas for the tail probabilities of the weak solutions S and T to these equations. In doing so we also obtain some by-products which are interesting in their own right. 相似文献
20.
Adam Osȩkowski 《Mediterranean Journal of Mathematics》2016,13(1):127-139
For any 1 < p < ∞ and any \({X, Y\in \mathbb{R}}\) satisfying \({|X|\leq Y}\) , we determine the optimal constant C p (X,Y) such that the following holds. If F is a holomorphic function on the unit disc satisfying ReF(0) = X and \({||{\rm Re}F||_{L^{p}(\mathbb{T})}=Y}\) , thenThis can be regarded as a reverse version of the classical estimates of Riesz and Essén. The proof rests on the exploitation of certain families of special subharmonic functions on the plane.
相似文献
$$||F||_{L^p(\mathbb{T})}\geq C_p(X,Y).$$