On normal control processes

Control processes of the form \(\dot x - A(t) x = B(t) u(t)\) , which are normal with respect to the unit ballB _{p′, r′} of the control spaceL ^p′([τ, T]),l _m ^r ′ are characterized in terms ofH(t)=X(T)X ^?1(t),B(t),X(t) any fundamental matrix solution of \(\dot x - A(t)x = 0\) , and directly in terms ofA, B, when bothA andB are independent oft.     

w* sequential convergence

LetX be an infinite dimensional Banach space, andX* its dual space. Sequences {χ _n ^* } _n=1 ^∞ ?X* which arew* converging to 0 while inf _n ‖x* _n ‖>0, are constructed.     

Metrische Räume mit Dreiseitverbindbaren

This paper presents a system of axioms for n-dimensional metric geometry. For every group satisfying the axioms there exist a group-space and an embedding of into a projective-metric space Ω. We construct an isomorphism of onto a subgroup of a special orthogonal group O _n+1 ^* (K,f). This group belongs to a metric vector space (V,f) over a field K of characteristic ≠ 2 where dim rad V≦1. The (full) groups o _n+1 ^* (K,f) are models of the system of axioms.     

Global convergence of a modified BFGS-type method for unconstrained non-convex minimization

To the unconstrained programme of non-convex function, this article give a modified BFGS algorithm associated with the general line search model. The idea of the algorithm is to modify the approximate Hessian matrix for obtaining the descent direction and guaranteeing the efficacious of the new quasi-Newton iteration equationB _k +1s _k =y _k ^* ,, wherey _k ^* is the sum ofy _k andA _k s _k , andA _k is some matrix. The global convergence properties of the algorithm associating with the general form of line search is proved.     

Solution of the Szili type conjugate problem on the roots of the laguerre polynomials

Let ?1<α≤0 and let $$L_n^{(\alpha )} (x) = \frac{1}{{n!}}x^{ - \alpha } e^x \frac{{d^n }}{{dx^n }}(x^{\alpha + n} e^{ - x} )$$ be the generalizednth Laguerre polynomial,n=1,2,… Letx ₁,x ₂,…,x _n andx*₁,x*₂,…,x* _n?1 denote the roots ofL _n ^(α) (x) andL _n ^(α)′ (x) respectively and putx*₀=0. In this paper we prove the following theorem: Ify ₀,y ₁,…,y _n ?1 andy ₁ ^′ ,…,y _n ^′ are two systems of arbitrary real numbers, then there exists a unique polynomialP(x) of degree 2n?1 satisfying the conditions $$\begin{gathered} P\left( {x_k^* } \right) = y_k (k = 0,...,n - 1) \hfill \\ P'\left( {x_k } \right) = y_k^\prime (k = 1,...,n). \hfill \\ \end{gathered} $$ .     

A new modification of the Hermite-Fejér interpolation

пУсть жАДАНы Ужлы $$ - \infty< x_1< x_2< ...< x_k< x_{k + 1}< ...< x_n< + \infty ,$$ , И пУстьx ₁ ^* <x ₂ ^* <...<x _n-1 ^* — кОРНИ МНОгО ЧлЕНА Ω′(х). гДЕ $$\omega (x) = \prod\limits_{k = 1}^n {(x - x_k ).} $$ В РАБОтЕ ИсслЕДУЕтсь жАДАЧА: кАк ОпРЕДЕлИт ь МНОгОЧлЕНР(х) МИНИМАльНОИ стЕп ЕНИ, Дль кОтОРОгО ВыпОлНь Утсь слЕДУУЩИЕ ИНтЕР пОльцИОННыЕ УслОВИь гДЕ {y _k И {y _k′}-жАДАННы Е сИстЕМы жНАЧЕНИИ.     

Yates type estimators of a common mean

Letx, y, S, T andW be independent random variables such that,～N(μασ ²),y～N(μ,βη ²), S/σ²～χ²(m), T/η²～χ²(n) andW/(ασ ²+βη²)～x²(q), where μ, σ², η² are unknown. For estimating μ, consider the estimator \(\hat \mu = x + \left( {y - x} \right){{aS} \mathord{\left/ {\vphantom {{aS} {\left[ {S + cT + d\left\{ {\left( {y - x} \right)^2 + W} \right\}} \right],a,c,d > 0}}} \right. \kern-0em} {\left[ {S + cT + d\left\{ {\left( {y - x} \right)^2 + W} \right\}} \right],a,c,d > 0}}\) . Note that the performance of \(\hat \mu \) depends onτ=βη ²/ασ², which is unknown. Assumeq+n≧2 and leta ₀=(n+q?1)/(m+2), c^*=cα/β, d^*=dα. Two main results are:

1. for all τ>0, \(\hat \mu \) has a variance smaller than that ofx ifa≦2 min (1,c ^*a₀, d^*a₀);
2. for all τ≧τ₀, where τ₀>0 is arbitrary, \(\hat \mu \) has a variance smaller than that ofx ifa≦2a ₀ min [c ^*τ₀/(1+τ₀),d^*].

We also obtain some necessary conditions for \(\hat \mu \) to have a variance smaller than that ofx. It can be seen that with the exception of linked block designs for any design belonging to the class calledD ₁-class by Shah [16], Yates-Rao estimator for recovery of interblock information has the same form as that of \(\hat \mu \) . Hence, for such designs the above results can be used to examine if Yates estimator is good i.e., better than the intra-block estimator. Shah [16] resolved this question for linked block designs, which include the symmetrical BIBD's. Here, we consider asymmetrical BIBD's and show that Yates' estimator is good for all such designs listed in Fisher and Yates' table [5], with two exceptions. For one of these two designs, we show that Yates' estimator is not uniformly better than the intra-block estimator.     

Generalized prolate spheroidal wave functions

The following equation $$(1 - x^2 )d^2 y/dx^2 + [(\beta - \alpha - (\alpha + \beta + 2)x]dy/dx + (\chi (c) - c^2 x^2 )y = 0$$ has been solved wherex(c) a separation constant is the characteristic value and is a function ofc. This solution is a generalization of spheroidal wave function into the series form ofP _n ^α;β (x),α andβ both separately are greater than ?1. The finite transform and its properties have been defined and a boundary value problem has been solved applying these tools.     

Interpolation in certain Hilbert spaces of analytic functions

In this article we study, for a Hilbert spaceB of analytic functions in the open unit disk, the dependence of the structure of the space of sequencesB(Z)={{f(z_k)} _k=1 ^∞ :f∈B} on the choice of the sequence Z={z_k} _k=1 ^∞ of distinct points of the unit disk [6].     

Reduced Load Equivalence under Subexponentiality

The stationary workload W _A+B ^φ of a queue with capacity φ loaded by two independent processes A and B is investigated. When the probability of load deviation in process A decays slower than both in B and $e^{ - \sqrt x } $ , we show that W _A+B ^φ is asymptotically equal to the reduced load queue W _A ^φ?b , where b is the mean rate of B. Given that this property does not hold when both processes have lighter than $e^{ - \sqrt x } $ deviation decay rates, our result establishes the criticality of $e^{ - \sqrt x } $ in the functional behavior of the workload distribution. Furthermore, using the same methodology, we show that under an equivalent set of conditions the results on sampling at subexponential times hold.     

Kantorovič operators of second order

The Kantorovi? operators of second order are introduced byQ _n f= =(B _n+2 F)″ whereF is the double indefinite integraloff andB _n+2 the (n+2)-th Bernstein operator. The operatorsQ _n will reveal a close affinity to the so-called modified Bernstein operatorsC _n introduced bySchnabl [10] on a quite different way. The article contains investigations concerning the asymptotic behavior ofQ _n ^kn f (asn → ∞), where (k _n) is a sequence of natural numbers.     

On the primes withp n+1 -p n = 8 and the Sum of their Reciprocals

We introduce the counting function π _2,8 ^* (x) of the primes with difference 8 between consecutive primes ( ****p _n,p_n+1 =p _n + 8) can be approximated by logarithm integralLi _2,8 ^* . We calculate the values of π _2,8 ^* (x) and the sumC _2,8(x) of reciprocals of primes with difference 8 between consecutive primes (p _n,p_n+1 =p _n +8)) wherex is counted up to 7 x 10¹⁰. From the results of these calculations, we obtain π _2,8 ^* (7 x 10¹⁰) = 133295081 andC _2,8(7 x 10¹⁰) = 0.3374 ±2.6 x 10^-4.     

On the cosets of the 2q-power group in the unit group modulop

Letp be a prime number ≡ 3 mod 4,G ^p the unit group of ?/p?, andg a generator ofG _p. Letq be an odd divisor ofp - 1 andG _p ^2q = {t ^2q;t ∈G _pthe subgroup of index2q inG _p. The groupG _p ² / _p ^2q consists of the classes \(\bar g^{2j} \) ,j = 0,...,q – 1. In this paper we study the ’excesses’ of the classes \(\bar g^{2j} \) in {l,...,(_p–l)/2}, i.e., the numbers \(\Phi _j = \left| {\left\{ {k;1 \leqslant k \leqslant \left( {p - 1} \right)/2,\bar k \in \bar g^{2j} } \right\}} \right| - \left| {\left\{ {k;\left( {p - 1} \right)/2 \leqslant k \leqslant p - 1,\bar k \in \bar g^{2j} } \right\}} \right|\) ,j = 0.....q — 1. First we express therelative class number h _2q of the subfieldK _2q? ?(e^2#x03C0;i/p ) of degree [K _2q: ?] =2q in terms of these excesses. We use this formula to establish certaincongruences for the Ф^j. E.g., ifq ∈ {3,5,11}, each number Фj is congruent modulo 4 to each other iff 2 dividesh _2q ^- . Finally we study thevariance of the excesses, i.e., the number \(\sigma ^2 = ((\Phi _0 - \hat \Phi )^2 + \ldots + (\Phi _{q - 1} - \hat \Phi )^2 )/(q - 1)\) , where \(\hat \Phi \) is the mean value of the numbers Ф_j. We obtain an explicit lower bound for σ² in terms ofh _2q ^- /h ₂ ^- . Moreover, we show that log σ² is asymptotically equal to 21og(h _2q ^- h ₂ ^- )/(q - 1) forp→∞. Three tables illustrate the results.     

Mehrfache gitterförmige Kreis- und Kugelanordnungen

LetG be a lattice inR ⁿ and letS ₁ ,S ₂ , ... be the family of unit spheres whose centres are the lattice-points ofG. This set is called ak-fold lattice packing (k-fold lattice covering) if each point ofR ⁿ lies in at most (at least)k of the open (closed) spheresS _i . Letd _k ⁿ be the density of the closestk-fold lattice packing and letD _k ⁿ be the density of the thinnestk-fold lattice covering ofR ⁿ . In the present paper we are considering the following problem: For which valuesn≧2 andk≧2 are the inequalitiesd _k ⁿ >kd ₁ ⁿ ,D _k ⁿ ₁ ⁿ valid?Theorem 1:For all pairs (n, k), n≧3, k≧2, with the exception of (3, k), (4, k), k=3, 5, 7, 9, 11 and (5, 3) we prove d _k ⁿ >kd ₁ ⁿ .Theorem 2:For each k≧3 is D _k ² ₁ ² . The proofs make use of the works ofBlundon, Danzer, Few andHeppes.     

Summability factors for lower-semi-matrix transformations

In view of Kogbetliantz's identity [7] the absolute Cesáro summability of orderk (k)>?1) of an infinite seriesΣ a _n is the same as the absolute convergence ofΣ(τ _n ^k )n ^?1 whereτ _n ^k is then-th Cesáro mean of orderk of sequence {na _n }.Das [5] has shown that similar dependence is true for certain classes of Nörlund means. The object of this paper is to establish two theorems on absolute summability factors involving two lower-semimatrix transformations and thereby to generalise a result ofChow [3] on absolute Cesáro summability factors and a result ofBosanquet andDas [1] on absolute Harmonic summability factors.     

Convolutions of random measures on compact groups

LetG be a compact group andM ₁(G) be the convolution semigroup of all Borel probability measures onG with the weak topology. We consider a stationary sequence {μ _n } _n=?∞ ^+∞ of random measures μ _n =μ _n (ω) inM ₁(G) and the convolutions $$v_{m,n} (\omega ) = \mu _m (\omega )* \cdots *\mu _{n - 1} (\omega ), m< n$$ and $$\alpha _n^{( + k)} (\omega ) = \frac{1}{k}\sum\limits_{i = 1}^k {v_{n,n + i} (\omega ),} \alpha _n^{( - k)} (\omega ) = \frac{1}{k}\sum\limits_{i = 1}^k {v_{n - i,n} (\omega )} $$ We describe the setsA _m ⁺ (ω) andA _n ⁺ (ω) of all limit points ofv _m,n(ω) asm→?∞ orn→+∞ and the setA _∞(ω) of its two-sided limit points for typical realizations of {μ _n (ω)} _n=?∞ ^+∞ . Using an appropriate random ergodic theorem we study the limit random measures ρ _n ^(±) (ω)=lim _k→∞ α _n ^(±k) (ω).     

Extreme instability of the horocycle flow

Let g be aC ³ negatively curved Riemannian metric on a compact connected orientable surfaceS. LetB be the collection of all metrics resulting from sufficiently small conformal changes of the metricg. (1) Then there is a constantA > 0 such that ifB then the \(\bar d\) distance between the horocycle flow? _t (Margulis parametrization) of (S, ?) and the rescaled horocycle flowh _ct of (S, g) is at leastA (?c > 0). No other dynamical system is known to have such extreme instability. (2) Fix ε > 0. Then there is anN > 0 so that if we are given samples {ξ} ₀ ^N {η} ₀ ^N which arose from the horocycle flows corresponding to two of the metrics?, g ∈B, then either the two samples are \(\bar d\) farther thanA/2 apart or the two surfaces are closer than ε. This holds even if these samples are slightly inaccurate.     

The annihilator of Bergman space

LetD be a bounded plane domain (with some smoothness requirements on its boundary). LetB _p(D), 1≤p<∞, be the Bergmanp-space ofD. In a previous paper we showed that the “natural projection”P, involving the Bergman kernel forD, is a bounded projection fromL _p(D) ontoB _p(D), 1<p<∞. With this we have the decompositionL _p(D)=B _p(D)⊕B _q ^⊥ (D,p ^–1+q ^–=1, 1<p< ∞. Here, we show that the annihilatorB _q ^⊥ (D) is the space of allL _p-complex derivatives of functions belonging to Sobolev space and which vanish on the boundary ofD. This extends a result of Schiffer for the casep=2. We also study certain operators onL _p(D). Especially, we show that , whereI is the identity operator and ? is an operator involving the adjoint of the Bergman kernel. Other relationships relevant toB _q ^⊥ (D) are studied.     

Tensor products of power Köthe spaces of different types

The multirectangular characteristics µ _m ^(λ,c) are applied to the isomorphic classification of tensor products of the form $ E_0 (a)\widehat \otimes E_\infty (b) $ . We single out a subclass of tensor products such that the two-rectangular characteristic µ ₂ ^(λ,c) is a complete invariant on this class.     

Singular integrals along Lipschitz curves with holomorphic kernels

If γ(x)=x+iA(x),tan ^?1‖A′‖_∞<ω<π/2,S _ω ⁰ ={z∈C}| |argz|<ω, or, |arg(-z)|<ω} We have proved that if φ is a holomorphic function in S _ω ⁰ and \(\left| {\varphi (z)} \right| \leqslant \frac{C}{{\left| z \right|}}\) , denotingT f (z)= ∫?(z-ζ)f(ζ)dζ, ?f∈C ₀(γ), ?z∈suppf, where C_c(γ) denotes the class of continuous functions with compact supports, then the following two conditions are equivalent:

1. T can be extended to be a bounded operator on L²(γ);
2. there exists a function ?₁ ∈H ^∞(S _ω ⁰ ) such that ?′₁(z)=?(z)+?(-z), ?z∈S _ω ⁰ ?z∈S _w ⁰ .