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1.
Let X1, …, Xp have p.d.f. g(x12 + … + xp2). It is shown that (a) X1, …, Xp are positively lower orthant dependent or positively upper orthant dependent if, and only if, X1,…, Xp are i.i.d. N(0, σ2); and (b) the p.d.f. of |X1|,…, |Xp| is TP2 in pairs if, and only if, In g(u) is convex. Let X1, X2 have p.d.f. f(x1, x2) = |Σ|?12 g((x1, x2) Σ?1(x1, x2)′). Necessary and sufficient conditions are given for f(x1, x2) to be TP2 for fixed correlation ?. It is shown that if f is TP2 for all ? >0. then (X1, X2)′ ~ N(0, Σ). Related positive dependence results and applications are also considered.  相似文献   

2.
Let X1, X2, X3, … be i.i.d. r.v. with E|X1| < ∞, E X1 = μ. Given a realization X = (X1,X2,…) and integers n and m, construct Yn,i, i = 1, 2, …, m as i.i.d. r.v. with conditional distribution P1(Yn,i = Xj) = 1n for 1 ? j ? n. (P1 denotes conditional distribution given X). Conditions relating the growth rate of m with n and the moments of X1 are given to ensure the almost sure convergence of (1mmi=1 Yn,i toμ. This equation is of some relevance in the theory of Bootstrap as developed by Efron (1979) and Bickel and Freedman (1981).  相似文献   

3.
If r, k are positive integers, then Tkr(n) denotes the number of k-tuples of positive integers (x1, x2, …, xk) with 1 ≤ xin and (x1, x2, …, xk)r = 1. An explicit formula for Tkr(n) is derived and it is shown that limn→∞Tkr(n)nk = 1ζ(rk).If S = {p1, p2, …, pa} is a finite set of primes, then 〈S〉 = {p1a1p2a2psas; piS and ai ≥ 0 for all i} and Tkr(S, n) denotes the number of k-tuples (x1, x3, …, xk) with 1 ≤ xin and (x1, x2, …, xk)r ∈ 〈S〉. Asymptotic formulas for Tkr(S, n) are derived and it is shown that limn→∞Tkr(S, n)nk = (p1 … pa)rkζ(rk)(p1rk ? 1) … (psrk ? 1).  相似文献   

4.
We show that under mild conditions the joint densities Px1,…,xn) of the general discrete time stochastic process Xn on pH can be computed via
Px1,…,xn(x1,…,xn) = 6?T(x1)…T(xn)62
where ? is in a Hilbert space pH, and T (x), x ? pH are linear operators on pH. We then show how the Central Limit Theorem can easily be derived from such representations.  相似文献   

5.
In this paper, the problem of phase reconstruction from magnitude of multidimensional band-limited functions is considered. It is shown that any irreducible band-limited function f(z1…,zn), zi ? C, i=1, …, n, is uniquely determined from the magnitude of f(x1…,xn): | f(x1…,xn)|, xi ? R, i=1,…, n, except for (1) linear shifts: i(α1z1+…+αn2n+β), β, αi?R, i=1,…, n; and (2) conjugation: f1(z11,…,zn1).  相似文献   

6.
Given a set S of positive integers let ZkS(t) denote the number of k-tuples 〈m1, …, mk〉 for which mi ∈ S ? [1, t] and (m1, …, mk) = 1. Also let PkS(n) denote the probability that k integers, chosen at random from S ? [1, n], are relatively prime. It is shown that if P = {p1, …, pr} is a finite set of primes and S = {m : (m, p1pr) = 1}, then ZkS(t) = (td(S))k Πν?P(1 ? 1pk) + O(tk?1) if k ≥ 3 and Z2S(t) = (td(S))2 Πp?P(1 ? 1p2) + O(t log t) where d(S) denotes the natural density of S. From this result it follows immediately that PkS(n) → Πp?P(1 ? 1pk) = (ζ(k))?1 Πp∈P(1 ? 1pk)?1 as n → ∞. This result generalizes an earlier result of the author's where P = ? and S is then the whole set of positive integers. It is also shown that if S = {p1x1prxr : xi = 0, 1, 2,…}, then PkS(n) → 0 as n → ∞.  相似文献   

7.
We show that CH implies that P(ω), 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 P(ω) such that (1) if α<β<ω1, then Xβ?1Xα; (2) if I ?ω1 is unaccountable, then there are distinct α, β ∈ I with Xβ ?Xα.  相似文献   

8.
The following estimate of the pth derivative of a probability density function is examined: Σk = 0Na?khk(x), where hk is the kth Hermite function and a?k = ((?1)pn)Σi = 1nhk(p)(Xi) is calculated from a sequence X1,…, Xn of independent random variables having the common unknown density. If the density has r derivatives the integrated square error converges to zero in the mean and almost completely as rapidly as O(n?α) and O(n?α log n), respectively, where α = 2(r ? p)(2r + 1). Rates for the uniform convergence both in the mean square and almost complete are also given. For any finite interval they are O(n?β) and O(n2log n), respectively, where β = (2(r ? p) ? 1)(2r + 1).  相似文献   

9.
Let ρ21,…,ρ2p be the squares of the population canonical correlation coefficients from a normal distribution. This paper is concerned with the estimation of the parameters δ1,…,δp, where δi = ρ2i(1 ? ρ2i), i = 1,…,p, in a decision theoretic way. The approach taken is to estimate a parameter matrix Δ whose eigenvalues are δ1,…,δp, given a random matrix F whose eigenvalues have the same distribution as r2i(1 ? r2i), i = 1,…,p, where r1,…,rp are the sample canonical correlation coefficients.  相似文献   

10.
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 X = Σi=1nXin be the sample mean. We derive the rate of convergence of Fn(X) to normality (for the regular as well as nonregular cases), a law of iterated logarithm, and an invariance principle for Fn(X).  相似文献   

11.
In this paper we study the linked nonlinear multiparameter system
yrn(Xr) + MrYr + s=1k λs(ars(Xr) + Prs) Yr(Xr) = 0, r = l,…, k
, where xr? [ar, br], yr is subject to Sturm-Liouville boundary conditions, and the continuous functions ars satisfy ¦ A ¦ (x) = detars(xr) > 0. Conditions on the polynomial operators Mr, Prs are produced which guarantee a sequence of eigenfunctions for this problem yn(x) = Πr=1kyrn(xr), n ? 1, which form a basis in L2([a, b], ¦ A ¦). Here [a, b] = [a1, b1 × … × [ak, bk].  相似文献   

12.
Let Ωm be the set of partitions, ω, of a finite m-element set; induce a uniform probability distribution on Ωm, and define Xms(ω) as the number of s-element subsets in ω. We alow the existence of an integer-valued function n=n(m)(t), t?[0, 1], and centering constants bms, 0?s? m, such that
Z(m)(t)=s=0n(m)(t)(Xms?bms)s=0mbms
converges to the ‘Brownian Bridge’ process in terms of its finite-dimensional distributions.  相似文献   

13.
Let {Xn}n≥1 be a sequence of independent and identically distributed random variables. For each integer n ≥ 1 and positive constants r, t, and ?, let Sn = Σj=1nXj and E{N(r, t, ?)} = Σn=1 nr?2P{|Sn| > ?nrt}. In this paper, we prove that (1) lim?→0+?α(r?1)E{N(r, t, ?)} = K(r, t) if E(X1) = 0, Var(X1) = 1, and E(| X1 |t) < ∞, where 2 ≤ t < 2r ≤ 2t, K(r, t) = {2α(r?1)2Γ((1 + α(r ? 1))2)}{(r ? 1) Γ(12)}, and α = 2t(2r ? t); (2) lim?→0+G(t, ?)H(t, ?) = 0 if 2 < t < 4, E(X1) = 0, Var(X1) > 0, and E(|X1|t) < ∞, where G(t, ?) = E{N(t, t, ?)} = Σn=1nt?2P{| Sn | > ?n} → ∞ as ? → 0+ and H(t, ?) = E{N(t, t, ?)} = Σn=1 nt?2P{| Sn | > ?n2t} → ∞ as ? → 0+, i.e., H(t, ?) goes to infinity much faster than G(t, ?) as ? → 0+ if 2 < t < 4, E(X1) = 0, Var(X1) > 0, and E(| X1 |t) < ∞. Our results provide us with a much better and deeper understanding of the tail probability of a distribution.  相似文献   

14.
Let L = ∑j = 1mXj2 be sum of squares of vector fields in Rn satisfying a Hörmander condition of order 2: span{Xj, [Xi, Xj]} is the full tangent space at each point. A point x??D of a smooth domain D is characteristic if X1,…, Xm are all tangent to ?D at x. We prove sharp estimates in non-isotropic Lipschitz classes for the Dirichlet problem near (generic) isolated characteristic points in two special cases: (a) The Grushin operator ?2?x2 + x2?2?t2 in R2. (b) The real part of the Kohn Laplacian on the Heisenberg group j ? 1n (??xj + 2yj??t)2 + (??yj ? 2xj??t)2 in R2n + 1. In contrast to non-characteristic points, C regularity may fail at a characteristic point. The precise order of regularity depends on the shape of ?D at x.  相似文献   

15.
16.
Let k and r be fixed integers such that 1 < r < k. Any positive integer n of the form n = akb, where b is r-free, is called a (k, r)-integer. In this paper we prove that if Qk,r(x) denotes the number of (k, r)-integers ≤ x, then Qk,r(x) = xζ(k)ζ(r) + Δk,r(x), where Δk,r(x) = O(x1rexp [?Blog35x (log log x)?15]), B being a positive constant depending on r and the O-estimate is uniform in k. On the assumption of the Riemann hypothesis, we improve the above order estimate of Δk,r(x) and prove that
1x1αδk,r(t)dt=0(x1kω(x))or0(x3/(4r+1)ω(x))
, according as k ≤ (4r + 1)3 or k > (4r + 1)3, where ω(x) = exp [B log x(log log x)?1].  相似文献   

17.
The probability generating function (pgf) of an n-variate negative binomial distribution is defined to be [β(s1,…,sn)]?k where β is a polynomial of degree n being linear in each si and k > 0. This definition gives rise to two characterizations of negative binomial distributions. An n-variate linear exponential distribution with the probability function h(x1,…,xn)exp(Σi=1n θixi)f(θ1,…,θn) is negative binomial if and only if its univariate marginals are negative binomial. Let St, t = 1,…, m, be subsets of {s1,…, sn} with empty ∩t=1mSt. Then an n-variate pgf is of a negative binomial if and only if for all s in St being fixed the function is of the form of the pgf of a negative binomial in other s's and this is true for all t.  相似文献   

18.
Let p, q be arbitrary parameter sets, and let H be a Hilbert space. We say that x = (xi)i?q, xi ? H, is a bounded operator-forming vector (?HFq) if the Gram matrixx, x〉 = [(xi, xj)]i?q,j?q is the matrix of a bounded (necessarily ≥ 0) operator on lq2, the Hilbert space of square-summable complex-valued functions on q. Let A be p × q, i.e., let A be a linear operator from lq2 to lp2. Then exists a linear operator ǎ from (the Banach space) HFq to HFp on D(A) = {x:x ? HFq, A〈x, x〉12 is p × q bounded on lq2} such that y = ǎx satisfies yj?σ(x) = {space spanned by the xi}, 〈y, x〉 = Ax, x〉 and 〈y, y〉 = A〈x, x〉12(A〈x, x〉12)1. This is a generalization of our earlier [J. Multivariate Anal.4 (1974), 166–209; 6 (1976), 538–571] results for the case of a spectral measure concentrated on one point. We apply these tools to investigate q-variate wide-sense Markov processes.  相似文献   

19.
For an n × n Hermitean matrix A with eigenvalues λ1, …, λn the eigenvalue-distribution is defined by G(x, A) := 1n · number {λi: λi ? x} for all real x. Let An for n = 1, 2, … be an n × n matrix, whose entries aik are for i, k = 1, …, n independent complex random variables on a probability space (Ω, R, p) with the same distribution Fa. Suppose that all moments E | a | k, k = 1, 2, … are finite, Ea=0 and E | a | 2. Let
M(A)=σ=1s θσPσ(A,A1)
with complex numbers θσ and finite products Pσ of factors A and A1 (= Hermitean conjugate) be a function which assigns to each matrix A an Hermitean matrix M(A). The following limit theorem is proved: There exists a distribution function G0(x) = G1x) + G2(x), where G1 is a step function and G2 is absolutely continuous, such that with probability 1 G(x, M(Ann12)) converges to G0(x) as n → ∞ for all continuity points x of G0. The density g of G2 vanishes outside a finite interval. There are only finitely many jumps of G1. Both, G1 and G2, can explicitly be expressed by means of a certain algebraic function f, which is determined by equations, which can easily be derived from the special form of M(A). This result is analogous to Wigner's semicircle theorem for symmetric random matrices (E. P. Wigner, Random matrices in physics, SIAM Review9 (1967), 1–23). The examples ArA1r, Ar + A1r, ArA1r ± A1rAr, r = 1, 2, …, are discussed in more detail. Some inequalities for random matrices are derived. It turns out that with probability 1 the sharpened form
lim supn→∞i=1ni(n)|2?6An62? 0.8228…
of Schur's inequality for the eigenvalues λi(n) of An holds. Consequently random matrices do not tend to be normal matrices for large n.  相似文献   

20.
Optimization problems are connected with maximization of three functions, namely, geometric mean, arithmetic mean and harmonic mean of the eigenvalues of (XΣX)?1ΣY(YΣY)?1YΣX, where Σ is positive definite, X and Y are p × r and p × s matrices of ranks r and s (≥r), respectively, and XY = 0. Some interpretations of these functions are given. It is shown that the maximum values of these functions are obtained at the same point given by X = (h1 + ?1hp, …, hr + ?rhp?r+1) and Y = (h1 ? ?1hp, …, hr ? ?rhp?r+1, Yr+1, …, Ys), where h1, …, hp are the eigenvectors of Σ corresponding to the eigenvalues λ1 ≥ λ2 ≥ … ≥ λp > 0, ?j = +1 or ?1 for j = 1,2,…, r and Yr+1, …, Ys, are linear functions of hr+1,…, hp?r. These results are extended to intermediate stationary values. They are utilized in obtaining the inequalities for canonical correlations θ1,…,θr and they are given by expressions (3.8)–(3.10). Further, some new union-intersection test procedures for testing the sphericity hypothesis are given through test statistics (3.11)–(3.13).  相似文献   

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