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1.
We show that CH implies that , when equipped with the Vietoris topology, has a subspace which is an L-space and a subspace which is an S-space. This is an immediate consequence of the following purely combinatorial result: CH implies the existence of an ω1-sequence 〈xα: α < ω1〉 in such that (1) if α<β<ω1, then ; (2) if I ?ω1 is unaccountable, then there are distinct α, β ∈ I with Xβ ?Xα. 相似文献
2.
For a class of subsets of a set X, let V() be the smallest n such that no n-element set F?X has all its subsets of the form A ∩ F, A ∈ . The condition V() <+∞ has probabilistic implications. If any two-element subset A of X satisfies both A ∩ C = Ø and A ? D for some C, D∈, then if and only if is linearly ordered by inclusion. If is of the form , i=1,2,…,n}, where each is linearly ordered by inclusion, then . If H is an (n-1)-dimensional affine hyperplane in an n-dimensional vector space of real functions on X, and is the collection of all sets {x: f(x)>0} for f in H, then . 相似文献
3.
Estimation d'une rupture en dépendance faibleChange point estimation for a weakly dependent sequence
Let be a stationary sequence governed by the model Yn=m(Xn)+σ(Xn)εn where is i.i.d. and independent from The latter sequence satisfy a weak dependence condition proposed by Doukhan and Louhichi in [2]. We provide a Central Limit Theorem for jumps in the regression function. Our method deals with linear local regression described in [4]. We use a variation on Lindeberg–Rio method as in [5]. To cite this article: P. Ango Nze, C. Prieur, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 267–270. 相似文献
4.
A family of of open subsets of the real line is called an ω-cover of a set X iff every finite subset of X is contained in an element of . A set of reals X is a γ-set iff for every ω-cover of X there exists such that In this paper we show that assuming Martin's axiom there is a γ-set X of cardinality the continuum. 相似文献
5.
Let H and K be symmetric linear operators on a C1-algebra with domains D(H) and D(K). H is defined to be strongly K-local if implies for A?D(H) ∩ D(K) and ω in the state space of , and H is completely strongly K-local if implies for A ∈ D(H) ∩ D(K) and Ω in the state of , and H is cpmpletely strongly K-local if is -local on U?Mn for all n ? 1, where n is the identity on the n × n matrices Mn. If is abelian then strong locality and complete strong locality are equivalent. The main result states that if τ is a strongly continuous one-parameter group of 1-automorphisms of with generator δ0 and δ is a derivation which commutes with τ and is completely strongly δ0-local then δ generates a group α of 1-automorphisms of . Various characterizations of α are given and the particular case of periodic τ is discussed. 相似文献
6.
7.
A compactificaton αX of a completely regular space X is “determined” by a subset F of C1(X) if αX is the smallest compactificaton of X to which each element of F extends, and is “generated” by F if the evaluation map , is an embedding and . Evidently, if F either determines or generates αX, then every elements of F has an extension to αX; whenever F satisfies this latter condition, the set of all such extensions is denoted Fα.A major results of our previous paper is that F determines αX if and only if Fα separates points of αX ? X. A major result of the present paper is that F generates αX if and only if Fα separates points of αX. 相似文献
8.
Roy Saunders Richard J. Kryscio Gerald M. Funk 《Stochastic Processes and their Applications》1981,12(1):97-106
Let X1n,…,X>nn denote the locations of n points in a bounded, γ-dimensional, Euclidean region Dn which has positive γ-dimensional Lebesgue measure μ(Dn). Let {Yn(r): r > 0} be the interpoint distance process for these points where Yn(r) is the number of pairs of points(Xin, Xin) which with i < j have Euclidean distance 6Xin ? X>in6 < r. In this article we study the limiting distribution of Yn(r) when n → ∞ and μ(Dn) → ∞, and the joint density of X1n,…,Xnnis of the form where r0 is a positive constant and Cn is a normalizing constant. These joint densities modify the Strauss [11] clustering model densities by introducing a hard-core component (no two points can have 6Xin ? Xin6 < r0) found in the Matérn [4] models. In our main result we show that the interpoint distance process converges to a non-homogeneous Poisson process for r values in a bounded interval 0 < r0 < r < r00 provided sparseness conditions discussed by Saunders and Funk [9] hold. The sparseness conditions which require converges to a positive constant and the boundary of Dn is negligible are essentially equivalent to requiring that although the number of points n is large the region is large enough so that the points are sparse in this region. That is, it is rare for a point to have another point close to it. These results extend results for v ? 0 given by Saunders and Funk [9] where it is shown that without the hard core component such results do not hold for v > 0. Statistical applications are discussed. 相似文献
9.
Let Fn(x) be the empirical distribution function based on n independent random variables X1,…,Xn from a common distribution function F(x), and let be the sample mean. We derive the rate of convergence of to normality (for the regular as well as nonregular cases), a law of iterated logarithm, and an invariance principle for . 相似文献
10.
Richard L. Tweedie 《Stochastic Processes and their Applications》1975,3(4):385-403
Let {Xn} be a ?-irreducible Markov chain on an arbitrary space. Sufficient conditions are given under which the chain is ergodic or recurrent. These extend known results for chains on a countable state space. In particular, it is shown that if the space is a normed topological space, then under some continuity conditions on the transition probabilities of {Xn} the conditions for ergodicity will be met if there is a compact set K and an ? > 0 such that whenever x lies outside K and is bounded, x ∈ K; whilst the conditions for recurrence will be met if there exists a compact K with for all x outside K. An application to queueing theory is given. 相似文献
11.
R.J. Williams 《Advances in Applied Mathematics》1985,6(1):1-3
Let {Xt, t ≥ 0} be Brownian motion in d (d ≥ 1). Let D be a bounded domain in d with C2 boundary, ?D, and let q be a continuous (if d = 1), Hölder continuous (if d ≥ 2) function in D?. If the Feynman-Kac “gauge” Ex{exp(∝0τDq(Xt)dt)1A(XτD)}, where τD is the first exit time from D, is finite for some non-empty open set A on ?D and some x?D, then for any ), is the unique solution in of the Schrödinger boundary value problem . 相似文献
12.
Let and denote respectively the space of n×n complex matrices and the real space of n×n hermitian matrices. Let p,q,n be positive integers such that p?q?n. For , the (p,q)-numerical range of A is the set , where Cp(X) is the pth compound matrix of X, and Jq is the matrix Iq?On-q. Let denote n or . The problem of determining all linear operators T: → such that is treated in this paper. 相似文献
13.
Palle E.T. Jørgensen 《Advances in Mathematics》1982,44(2):105-120
Let Ω be an arbitrary open subset of n of finite positive measure, and assume the existence of a subset Λ ? n such that the exponential functions eλ = exp i(λ1x1 + … + λnxn), λ = (λ1,…, λn) ∈ Λ, form an orthonormal basis for with normalized measure. Assume 0 ∈ Λ and define subgroups K and A of (n, +) by K = Λ0 = {γ ∈ n:γ·λ ∈ 2π}, A = {a ∈ n:Ua U1a = }, where Ut is the unitary representation of n on given by Ute = eitλeλ, t ∈ n, λ ∈ Λ, and where is the multiplication algebra of on L2. Assume that A is discrete. Then there is a discrete subgroup D ? A of dimension n, a fundamental domain for D, and finite sets of representers RΛ, RΓ, , each containing 0, RΛ for in K0, and for in A such that Ω is disjoint union of translates of : Ω = ∪a∈RΩ (a + ), neglecting null sets, and Λ = RΛ ⊕ D0. If RΓ is a set of representers for in D, then Γ = RΓ ⊕ K is a translation set for Ω, i.e., Ω ⊕ Γ = n, direct sum, (neglecting null sets). The case A = n corresponds to Ω = , Λ = D0 and Γ = K. This last case corresponds in turn to a function theoretic assumption of Forelli. 相似文献
14.
For matrices , the C-numerical radius of A is the nonnegative quantity . This generalizes the classical numerical radius r(A). It is known that rc constitutes a norm on if and only if C is nonscalar and trC≠0. For all such C we obtain multiplicativity factors for rc, i.e., constant μ>0 for which μrc is submultiplicative on . 相似文献
15.
Harry Cohn 《Stochastic Processes and their Applications》1981,12(1):59-72
It is shown that any real-valued sequence of random variables {Xn} converging in probability to a non-degenerate, not necessarily a.s. finite limit X possesses the following property: for any c with P(X? (c ? δ, c + δ)) > 0 for all δ > 0, there exists a sequence {cn} with limn→∞ cn = c such that for any ε > 0, limn→∞ P(Xδ (c ? ε, c + ε) |Xn = cn) = 1. This property is applied to various types of branching processes where or being a sequence of constants or random variables and U a slowly varying function. If {Zn} is a supercritical branching process in varying or random environment, X is shown to have a continuous and strictly increasing distribution function on (0, ∞). Characterizations of the tail of the liniting distribution of the finite mean and the infinite mean supercritical Galton-Watson processes are also obtained. 相似文献
16.
A pair (,U) consisting of a category with coequalizers and a functor U: → Set is a weak quasi-variety if U has a left adjoint and U preserves and reflects regular epis. It is known that every weak quasi-variety is equivalent to a concrete quasi-variety, i.e. a category of Σ-algebras which has all free algebras and which is closed with respect to products and subalgebras. It is also known that if U preserves monic direct limits, is equivalent to a concrete quasi-variety of Σ-algebras in which Σ contains no function symbols of infinite rank; and if U preserves all direct limits, is equivalent to a concrete quasi-variety of Σ-algebras definable by a set of implications of the form where ti and si are Σ-terms and m is a nonnegative integer. This paper concerns several definitions of ‘finiteness’ in a category theoretic setting and some theorems on weak quasi-varieties. Two main theorems characterize those weak quasi-varieties (, U) such that U preserves all direct limits. 相似文献
17.
Hermann König 《Journal of Functional Analysis》1977,24(1):32-51
For an open set Ω ? N, 1 ? p ? ∞ and λ ∈ +, let denote the Sobolev-Slobodetzkij space obtained by completing in the usual Sobolev-Slobodetzkij norm (cf. A. Pietsch, “r-nukleare Sobol. Einbett. Oper., Ellipt. Dgln. II,” Akademie-Verlag, Berlin, 1971, pp. 203–215). Choose a Banach ideal of operators , 1 ? p, q ? ∞ and a quasibounded domain Ω ? N. Theorem 1 of the note gives sufficient conditions on λ such that the Sobolev-imbedding map exists and belongs to the given Banach ideal : Assume the quasibounded domain fulfills condition Ckl for some l > 0 and 1 ? k ? N. Roughly this means that the distance of any to the boundary ?Ω tends to zero as for , and that the boundary consists of sufficiently smooth ?(N ? k)-dimensional manifolds. Take, furthermore, 1 ? p, q ? ∞, p > k. Then, if μ, ν are real positive numbers with λ = μ + v ∈ , μ > λ S(; p,q:N) and v > N/l · λD(;p,q), one has that belongs to the Banach ideal . Here λD(;p,q;N)∈+ and λS(;p,q;N)∈+ are the D-limit order and S-limit order of the ideal , introduced by Pietsch in the above mentioned paper. These limit orders may be computed by estimating the ideal norms of the identity mappings lpn → lqn for n → ∞. Theorem 1 in this way generalizes results of R. A. Adams and C. Clark for the ideals of compact resp. Hilbert-Schmidt operators (p = q = 2) as well as results on imbeddings over bounded domains.Similar results over general unbounded domains are indicated for weighted Sobolev spaces.As an application, in Theorem 2 an estimate is given for the rate of growth of the eigenvalues of formally selfadjoint, uniformly strongly elliptic differential operators with Dirichlet boundary conditions in , where Ω fulfills condition C1l.For an open set Ω in N, let denote the Sobolev-Slobodetzkij space obtained by completing in the usual Sobolev-Slobodetzkij norm, see below. Taking a fixed Banach ideal of operators and 1 ? p, q ? ∞, we consider quasibounded domains Ω in N and give sufficient conditions on λ such that the Sobolev imbedding operator exists and belongs to the Banach ideal. This generalizes results of C. Clark and R. A. Adams for compact, respectively, Hilbert-Schmidt operators (p = q = 2) to general Banach ideals of operators, as well as results on imbeddings over bounded domains. Similar results over general unbounded domains may be proved for weighted Sobolev spaces. As an application, we give an estimate for the rate of growth of the eigenvalues of formally selfadjoint, uniformly strongly elliptic differential operators with Dirichlet boundary conditions in , where Ω is a quasibounded open set in N. 相似文献
18.
Given a polynomial , we calculate a subspace Gp of the linear space 〈X〉 generated by the indeterminates which is minimal with respect to the property (the algebra generated by Gp, and prove its uniqueness. Furthermore, we use this result to characterize the pairs (P,Q) of polynomials P(X1,…,Xn) and Q(X1,…,Xn) for which there exists an isomorphism T:〈X〉 →〈X〉 that “separates P from Q,” i.e., such that for some k(1<k<n) we can write P and Q as and respectively, where . 相似文献
19.
Derek W Robinson 《Journal of Functional Analysis》1977,24(3):280-290
Let U, V be two strongly continuous one-parameter groups of bounded operators on a Banach space with corresponding infinitesimal generators S, T. We prove the following: ∥Ut, ? Vt ∥ = O(t), t → 0, if and only if U = V; ∥Ut ? Vt∥ = O(tα), t → 0; with 0 ? α ? 1, if and only if , where Ω, P, are bounded operators on such that if and only if has a bounded extension to 1. Further results of this nature are inferred for semigroups, reflexive spaces, Hilbert spaces, and von Neumann algebras. 相似文献
20.
P. Révész 《Stochastic Processes and their Applications》1983,15(2):169-179
Let U1, U2,… be a sequence of independent, uniform (0, 1) r.v.'s and let R1, R2,… be the lengths of increasing runs of {Ui}, i.e., X1=R1=inf{i:Ui+1<Ui},…, Xn=R1+R2+?+Rn=inf{i:i>Xn?1,Ui+1<Ui}. The first theorem states that the sequence can be approximated by a Wiener process in strong sense.Let τ(n) be the largest integer for which R1+R2+?+Rτ(n)?n, and . Here Mn is the length of the longest increasing block. A strong theorem is given to characterize the limit behaviour of Mn.The limit distribution of the lengths of increasing runs is our third problem. 相似文献