Unconditional and symmetric sets inn-dimensional normed spaces

Isoperimetric inequalities are used to obtain measure estimates on almost constancy sets of functions on product spaces. These are applied to produce almost unconditional or symmetric block sequences from given sequences. Their length, which is (logn)^1/2 in the general case, improves ton ^a where a cotype condition is imposed or when the given sequences arep-type attaining for somep<2. In thep-type attaining case, block sequences (1+ε)-equivalent to the unit vector basis ofl _p ^m can be obtained when log logm ∼ log logn. Research supported in part by NSF Grant MCS 7902489.     

A note on eigenvalues of random block Toeplitz matrices with slowly growing bandwidth

This paper can be thought of as a remark of Li et al. (2010), where the authors studied the eigenvalue distribution μ_XN of random block Toeplitz band matrices with given block order m. In this paper, we will give explicit density functions of lim_N→∞μ_XN when the bandwidth grows slowly. In fact, these densities are exactly the normalized one-point correlation functions of m×m Gaussian unitary ensemble (GUE for short). The series {lim_N→∞μ_XN∣m∈N} can be seen as a transition from the standard normal distribution to semicircle distribution. We also show a similar relationship between GOE and block Toeplitz band matrices with symmetric blocks.     

Lp-Approximable Sequences of Vectors and Limit Distribution of Quadratic Forms of Random Variables

The properties of L₂-approximable sequences established here form a complete toolkit for statistical results concerning weighted sums of random variables, where the weights are nonstochastic sequences approximated in some sense by square-integrable functions and the random variables are “two-wing” averages of martingale differences. The results constitute the first significant advancement in the theory of L₂-approximable sequences since 1976 when Moussatat introduced a narrower notion of L₂-generated sequences. The method relies on a study of certain linear operators in the spaces L_p and l_p. A criterion of L_p-approximability is given. The results are new even when the weight generating function is identically 1. A central limit theorem for quadratic forms of random variables illustrates the method.     

Distribution of 0 and 1 in the highest level of primitive sequences over ℤ/(2e)

The distribution of 0 and 1 is studied in the highest levela _e-1 of primitive sequences overZ /(2^e). and the upper and lower bounds on the ratio of the number of 0 to the number of 1 in one period ofa _e-1, are obtained. It is revealed that the largere is, the closer to 1 the ratio will be. Project supported by the State Key Laboratory of Information Security, Graduate School of Chinese Academy of Sciences.     

Limiting distribution of sums of nonnegative stationary random variables

Summary Let {X _n,j,−∞<j<∞∼,n≧1, be a sequence of stationary sequences on some probability space, with nonnegative random variables. Under appropriate mixing conditions, it is shown thatS _n=X_n,1+…+X _n,n has a limiting distribution of a general infinitely divisible form. The result is applied to sequences of functions {f _n(x)∼ defined on a stationary sequence {X _j∼, whereX _n.f=f_n(X_j). The results are illustrated by applications to Gaussian processes, Markov processes and some autoregressive processes of a general type. This paper represents results obtained at the Courant Institute of Mathematical Sciences, New York University, under the sponsorship of the National Sciences Foundation, Grant MCS 82-01119.     

An analogue of Montel's theorem for some classes of rational functions

For sequences of rational functions, analytic in some domain, a theorem of Montel's type is proved. As an application, sequences of rational functions of the best L _p -approximation with an unbounded number of finite poles are considered.     

On large half-factorial sets in elementary<Emphasis Type="Italic">p</Emphasis>-groups: Maximal cardinality and structural characterization

Half-factoriality is a central concept in the theory of non-unique factorization, with applications for instance in algebraic number theory. A subsetG ₀ of an abelian group is called half-factorial if the block monoid overG ₀, which is the monoid of all zero-sum sequences of elements ofG ₀, is a half-factorial monoid. In this paper we study half-factorial sets with large cardinality in elementaryp-groups. First, we determine the maximal cardinality of such half-factorial sets, and generalize a result which has been only known for groups of even rank. Second, we characterize the structure of all half-factorial sets with large cardinality (in a sense made precise in the paper). Both results have a direct application in the study of some counting functions related to factorization properties of algebraic integers. This work was supported by the Austrian Science Fund FWF (Project P16770-N12) and by the Austrian-French Program ‘Amadeus 2003–2004’.     

Inequalities for the expectation of Δ-monotone functions

Summary For some subsets of the set of all -monotone functions on [0,1] ⁿ we characterize distribution functions F, G such that E _F fE_G f for all f within these subsets. Furthermore, we determine sharp upper and lower bounds of integrals of functions in these subsets w.r.t. all distributions with fixed marginals and give some applications of these results.     

О локализации прибли жений функций тригонометрическим и полиномами

For periodic functions, sequences of trigonometric polynomialsP _m (x) are constructed which provide close-to-best approximation on the whole period and such that if on a certain interval the function possesses better properties, thenP _m (x) approximate it inside of this interval at a higher rate of convergence than on the whole period. The results of this article extend investigations by S. Bochner, T. Frey, and V. Ja. Janak.     

Interpolation problems on the spectrum of <Emphasis Type="Italic">H</Emphasis><Superscript>∞</Superscript>

We characterize those sequences (x _n ) in the spectrum of H ^∞ whose Nevanlinna–Pick interpolation problems admit thin Blaschke products as solutions. We also study under which conditions there is a Blaschke product B with prescribed zero-set distribution and solving problems of the form B(x) = f _n (x) for every x ∈ P(x _n ), where P(x _n ) is the Gleason part associated with the point x _n and where (f _n ) is an arbitrary sequence of functions in the unit ball of H ^∞. As a corollary we get a new characterization of Carleson–Newman Blaschke products in terms of bounded universal functions, a result first proved by Gallardo and Gorkin.      

Benford’s law and distribution functions of sequences in (0, 1)

Applying the theory of distribution functions of sequences x _n ∈ [0, 1], n = 1, 2, ..., we find a functional equation for distribution functions of a sequence x _n and show that the satisfaction of this functional equation for a sequence x _n is equivalent to the fact that the sequence x _n to satisfies the strong Benford law. Examples of distribution functions of sequences satisfying the functional equation are given with an application to the strong Benford law in different bases. Several direct consequences from uniform distribution theory are shown for the strong Benford law.     

Entropy conditions for subsequences of random variables with applications to empirical processes

We introduce new entropy concepts measuring the size of a given class of increasing sequences of positive integers. Under the assumption that the entropy function of is not too large, many strong limit theorems will continue to hold uniformly over all sequences in . We demonstrate this fact by extending the Chung-Smirnov law of the iterated logarithm on empirical distribution functions for independent identically distributed random variables as well as for stationary strongly mixing sequences to hold uniformly over all sequences in . We prove a similar result for sequences (n _k ω) mod 1 where the sequence (n _k ) of real numbers satisfies a Hadamard gap condition. Authors’ addresses: István Berkes, Department of Statistics, Technical University Graz, Steyrergasse 17/IV, A-8010 Graz, Austria; Walter Philipp, Department of Statistics, University of Illinois, 725 S. Wright Street, Champaign, IL 61820, USA; Robert F. Tichy, Department of Analysis and Computational Number Theory, Technical University Graz, Steyrergasse 30, A-8010 Graz, Austria     

Interpolation problems on the spectrum of H∞

We characterize those sequences (x _n ) in the spectrum of H ^∞ whose Nevanlinna–Pick interpolation problems admit thin Blaschke products as solutions. We also study under which conditions there is a Blaschke product B with prescribed zero-set distribution and solving problems of the form B(x) = f _n (x) for every x ∈ P(x _n ), where P(x _n ) is the Gleason part associated with the point x _n and where (f _n ) is an arbitrary sequence of functions in the unit ball of H ^∞. As a corollary we get a new characterization of Carleson–Newman Blaschke products in terms of bounded universal functions, a result first proved by Gallardo and Gorkin.     

The Extended Probability Generating Functional,with Application to Mixing Properties of Cluster Point Processes

An extended probability generating functional (p. g. fl.) \documentclass{article}\pagestyle{empty}\begin{document}$ \bar{G}[h]\; = \;E\;\left({\exp \;\int\limits_x {\log } \;h(x)\; \times \;N(dx)} \right) $\end{document} is well-defined for any point process N on the complete separable metric space χ over the space V?₀ of measurable functions h: χ → (0, 1) such that inf x cH h(x) > 0. The distribution of N is determined uniquely by the p.g.fl. G[h] ≡ ?[h] over the smaller space V₀ of functions h ε V?₀ for which 1 — h has bounded support. Continuity results for ?[·] involving pointwise convergent sequences {h_n} V₀ or V?₀ or V? ≡ {measurable h: χ → [0, 1]} or V = {h ε V?: 1 — h has bounded support} are reviewed, and used in furnishing a complete p. g. fl. proof of the mixing property of certain stationary cluster processes.     

Summability of Lagrange type interpolation series

We consider certain aspects of the theory of interpolation via entire functions of exponential type, which include sampling node sequences χ which can be highly irregular and data sequences {y(_x)}_xn∈χ which are not necessarily bounded. Under appropriate conditions, we show that there is an entire function of a suitable exponential type which uniquely interpolates the data and indicate the validity of certain summabilty methods for the corresponding Lagrange type interpolation series. Some of our results significantly extend the work of Schoenberg,Cardinal interpolation and spline functions VII: The behavior of cardinal spline interpolation as their degree tends to infinity, J. Analyse Math.27 (1974), 205–229.     

Coding into Ramsey sets

In [6] W. T. Gowers formulated and proved a Ramsey-type result which lies at the heart of his famous dichotomy for Banach spaces. He defines the notion of weakly Ramsey set of block sequences of an infinite dimensional Banach space and shows that every analytic set of block sequences is weakly Ramsey. We show here that Gowers’ result follows quite directly from the fact that all G_δ sets are weakly Ramsey, if the Banach space does not contain c₀, and from the fact that all F_σδ sets are weakly Ramsey, in the case of an arbitrary Banach space. We also show that every result obtained by the application of Gowers’ theorem to an analytic set can also be obtained by applying the Theorem to a F_σδ set (or to a G_δ set if the space does not contain c₀). This fact explains why the only known applications of this technique are based on very low-ranked Borel sets (open, closed, F_σ, or G_δ).     

Universal functions for composition operators with non-automorphic symbol

For sequences (φ _n ) of eventually injective holomorphic self-maps of planar domains Ω, we present necessary and sufficient conditions for the existence of holomorphic functions f on whose orbits under the action of (φ _n ) are dense in H (Ω). It is deduced that finitely connected, but non-simply connected domains never admit such universal functions. On the other hand, if we allow arbitrary sequences of holomorphic self-maps (φ _n ), the situation changes dramatically.     

On symmetric basic sequences in lorentz sequence spaces II

It is shown that if {y _n} is a block of type I of a symmetric basis {x _n} in a Banach spaceX, then {y _n} is equivalent to {x _n} if and only if the closed linear span [y _n] of {y _n} is complemented inX. The result is used to study the symmetric basic sequences of the dual space of a Lorentz sequence spaced(a, p). Let {x _n,f _n} be the unit vector basis ofd(a, p), for 1≤p<+∞. It is shown that every infinite-dimensional subspace ofd(a, p) (respectively, [f _n] has a complemented subspace isomorphic tol _p (respectively,l _q, 1/p+1/q=1 when 1<p<+∞ andc ₀ whenp=1) and numerous other results on complemented subspaces ofd(a, p) and [f _n] are obtained. We also obtain necessary and sufficient conditions such that [f _n] have exactly two non-equivalent symmetric basic sequences. Finally, we exhibit a Banach spaceX with symmetric basis {x _n} such that every symmetric block basic sequence of {x _n} spans a complemented subspace inX butX is not isomorphic to eitherc ₀ orl _p, 1≤p<+∞.     

Some characterizations of unimodal distribution functions

Let F be a distribution function and let Q _F(l)=0 for l<0 and Q _F(l)= sup {F(x+l)–F(x): x} for l0 be its Lévy concentration function. This paper has two purposes: to give a characterization of unimodal distribution functions (Theorem 3.5) and a representation theorem for the class of unimodal distribution functions (Theorem 6.2), both in terms of their Lévy concentration functions.Work supported by the Natural Sciences and Engineering Research Council Canada Grants A-7339 and A-7223, by the Québec Action Concertée Grant ER-1023, and by the Deutsche Forschungsgemeinschaft