Simple continued fractions for some irrational numbers,II

In this paper we prove a theorem allowing us to determine the continued fraction expansion for Σ_k=0^∞u^?c(k), where c(k) is any sequence of positive integers that grows sufficiently quickly. As an application, we determine the continued fraction expansion for Liouville's famous transcendental number Σ_k=0^∞m^{?(k + 1)!}.     

Пространства Lp со сме шанной нормой на беск онечном декартовом произвед ении вероятностных п ространств

Letp=(p ₁,p₂,...) be a vector with an infinite number of coordinates, 1≦p _k≦,k=1,2,... On the set of random functions depending on infinite number of variables, a mixed norm ∥.∥ _p is introduced, and thus the spacesL _p with mixed norm are defined. Part 1 contains observations of general properties of those spaces (in particular, convergence properties depending on the behaviour of the exponentsp _k ask→ ∞). Part 2 contains the proof of infinite-dimensional version of S. L. Sobolev's theorem (in mixed norm) for potentials of Wiener semigroup on infinite dimensional torusT ^∞.     

On the central limit theorem for f (n k x)

By a classical observation in analysis, lacunary subsequences of the trigonometric system behave like independent random variables: they satisfy the central limit theorem, the law of the iterated logarithm and several related probability limit theorems. For subsequences of the system ( f (nx)) _n≥1 with 2π-periodic ${f\in L^2}$ this phenomenon is generally not valid and the asymptotic behavior of ( f (n _k x)) _k≥1 is determined by a complicated interplay between the analytic properties of f (e.g., the behavior of its Fourier coefficients) and the number theoretic properties of n _k . By the classical theory, the central limit theorem holds for f (n _k x) if n _k  = 2 ^k , or if n _k+1/n _k → α with a transcendental α, but it fails e.g., for n _k  = 2 ^k  ? 1. The purpose of our paper is to give a necessary and sufficient condition for f (n _k x) to satisfy the central limit theorem. We will also study the critical CLT behavior of f (n _k x), i.e., the question what happens when the arithmetic condition of the central limit theorem is weakened “infinitesimally”.     

On arrangements of roots for a real hyperbolic polynomial and its derivatives

In this paper we count the number ?_n^(0,k), k?n−1, of connected components in the space Δ_n^(0,k) of all real degree n polynomials which a) have all their roots real and simple; and b) have no common root with their kth derivatives. In this case, we show that the only restriction on the arrangement of the roots of such a polynomial together with the roots of its kth derivative comes from the standard Rolle's theorem. On the other hand, we pose the general question of counting all possible root arrangements for a polynomial p(x) together with all its nonvanishing derivatives under the assumption that the roots of p(x) are real. Already the first nontrivial case n=4 shows that the obvious restrictions coming from the standard Rolle's theorem are insufficient. We prove a generalized Rolle's theorem which gives an additional restriction on root arrangements for polynomials.     

Some applications of Montgomery's sieve

Artin has conjectured that every positive integer not a perfect square is a primitive root for some odd prime. A new estimate is obtained for the number of integers in the interval [M + 1, M + N] which are not primitive roots for any odd prime, improving on a theorem of Gallagher.Erd?s has conjectured that 7, 15, 21, 45, 75, and 105 are the only values of the positive integer n for which n ? 2^k is prime for every k with 1 ≤ k ≤ log₂n. An estimate is proved for the number of such n ≤ N.     

Collinear subsets of lattice point sequences—An analog of Szemerédi's theorem

Szemerédi's theorem states that given any positive number B and natural number k, there is a number n(k, B) such that if n ? n(k, B) and 0 < a₁ < … < a_n is a sequence of integers with a_n ? Bn, then some k of the a_i form an arithmetic progression. We prove that given any B and k, there is a number m(k, B) such that if m ? m(k, B) and u₀, u₁, …, u_m is a sequence of plane lattice points with ∑_i=1^m…u_i ? u_i?1… ? Bm, then some k of the u_i are collinear. Our result, while similar to Szemerédi's theorem, does not appear to imply it, nor does Szemerédi's theorem appear to imply our result.     

A theorem relating potential and bell polynomials

We define the potential polynomial F^(z)_k and the exponential Bell polynomial B_n,j (0,...,0, ?_r?_r+1,...) and we prove a theorem relating the two. Though not well-known, the theorem has many applications, some of which we discuss in this paper. In particular, the theorem provides a systematic approach to a number of formulas and identities involving Stirling numbers and associated Stirling numbers.     

On a class of degenerate extremal graph problems

Given a class ? of (so called “forbidden”) graphs, ex (n, ?) denotes the maximum number of edges a graphG ⁿ of ordern can have without containing subgraphs from ?. If ? contains bipartite graphs, then ex (n, ?)=O(n ^2?c ) for somec>0, and the above problem is calleddegenerate. One important degenerate extremal problem is the case whenC _2k , a cycle of 2k vertices, is forbidden. According to a theorem of P. Erd?s, generalized by A. J. Bondy and M. Simonovits [3₂, ex (n, {C _2k })=O(n ^1+1/k ). In this paper we shall generalize this result and investigate some related questions.     

Almost sure central limit theory for products of sums of partial sums

Consider a sequence of i.i.d. positive random variables. An universal result in almost sure limit theorem for products of sums of partial sums is established.We will show that the almost sure limit the...     

The Product of Like-Indexed Terms in Binary Recurrences

In recent work by Hajdu and Szalay, Diophantine equations of the form (a^k−1)(b^k−1)=x² were completely solved for a few pairs (a, b). In this paper, a general finiteness theorem for equations of the form u_kv_k=xⁿ is proved, where u_k and v_k are terms in certain types of binary recurrence sequences. Also, a unified computational approach for solving equations of the type (a^k−1)(b^k−1)=x² is described, and this approach is used to completely solve such equations for almost all (a,b) in the range 1<a<b?100. In the final section of this paper, it is shown that the abc conjecture implies much stronger results on these types of Diophantine problems.     

On generalized Heawood inequalities for manifolds: a van Kampen–Flores-type nonembeddability result

The fact that the complete graph K₅ does not embed in the plane has been generalized in two independent directions. On the one hand, the solution of the classical Heawood problem for graphs on surfaces established that the complete graph K_n embeds in a closed surface M (other than the Klein bottle) if and only if (n?3)(n?4) ≤ 6b₁(M), where b₁(M) is the first Z₂-Betti number of M. On the other hand, van Kampen and Flores proved that the k-skeleton of the n-dimensional simplex (the higher-dimensional analogue of K_n+1) embeds in R^2k if and only if n ≤ 2k + 1.Two decades ago, Kühnel conjectured that the k-skeleton of the n-simplex embeds in a compact, (k ? 1)-connected 2k-manifold with kth Z₂-Betti number b_k only if the following generalized Heawood inequality holds: ( _k+1 ^n?k?1 ) ≤ ( _k+1 ^2k+1 )b_k. This is a common generalization of the case of graphs on surfaces as well as the van Kampen–Flores theorem.In the spirit of Kühnel’s conjecture, we prove that if the k-skeleton of the n-simplex embeds in a compact 2k-manifold with kth Z₂-Betti number bk, then n ≤ 2b_k( _k ^2k+2 )+2k+4. This bound is weaker than the generalized Heawood inequality, but does not require the assumption that M is (k?1)-connected. Our results generalize to maps without q-covered points, in the spirit of Tverberg’s theorem, for q a prime power. Our proof uses a result of Volovikov about maps that satisfy a certain homological triviality condition.     

An improvement of the octonionic Taylor type theorem

We prove that the octonionic polynomials V ■k l 1 ··· l k are independent of the associative orders ■k . This improves the octonionic Taylor type theorem.     

Lucas's criterion for the primality of numbers of the form N = h2n−1

The following theorem is proved. Let N = h2ⁿ-1, where n ≥ 2, h is odd, 1 <-h < 2ⁿ, and suppose that v is a positive integer, v ≥ 3,α is a root of the equation $$(v^2 - 4,N) = 1,\left( {\frac{{v - 2}}{N}} \right) = 1,\left( {\frac{{v + 2}}{N}} \right) = - 1$$ . Then for N to be prime, it is necessary and sufficient that s_n?2≡0(modN), where S_k+1=S _k ² ? 2 (k = 0, 1...), s_o=a^h+ a^?h. For given N, an algorithm is described for the construction of the smallest v satisfying the conditions of this theorem.     

Decompositions of complete graphs into regular bichromatic factors

The proof of the following theorem is given: A complete graph with n vertices can be decomposed into r regular bichromatic factors if and only if n is even and greater than 4 and there exists a natural number k with the properties that k ≤ r and 2^{k ? 1} < n ≤ 2^k.     

Spectral bounds for the clique and independence numbers of graphs

We obtain a sequence k₁(G) ≤ k₂(G) ≤ … ≤ k_n(G) of lower bounds for the clique number (size of the largest clique) of a graph G of n vertices. The bounds involve the spectrum of the adjacency matrix of G. The bound k₁(G) is explicit and improves earlier known theorems. The bound k₂(G) is also explicit, and is shown to improve on the bound from Brooks' theorem even for regular graphs. The bounds k₃,…, k_r are polynomial-time computable, where r is the number of positive eigenvalues of G.     

Disjoint matchings of graphs

In this paper, we prove a generalization of the familiar marriage theorem. One way of stating the marriage theorem is: Let G be a bipartite graph, with parts S₁ and S₂. If A ? S₁ and F(A) ? S₂ is the set of neighbors of points in A, then a matching of G exists if and only if Σ_x∈S2 min(1, | F^?1(x) ∩ A |) ≥ | A | for each A ? S₁. Our theorem is that k disjoint matchings of G exist if and only Σ_x∈S2 min (k, | F^?1(x) ∩ A |) ≥ k | A | for each A ? S₁.     

On a theorem of silver

A recent theorem of Silver, in its simplest form, states, that if ω < cf(k) < k and 2^λ=λ⁺ for all λ < k, then 2^k=k⁺. Silver's proof employs Boolean-valued as well as nonstandard models of set theory. In the present note we give an elementary proof of Silver's theorem in its general form.     

Extending t-designs

Three extension theorems for t-designs are proved; two for t even, and one for t odd. Another theorem guaranteeing that certain t-designs be (t + 1)-designs is presented. The extension theorem for odd t is used to show that every group of odd order 2k + 1, k ≠ 2^r ? 1, acts as an automorphism group of a 2-(2k + 2, k + 1, λ) design consisting of exactly one half of the (k + 1)-settled, Although the question of the existence of a 6-(14, 7, 4) design is not settled, certain requisite properties of the 4-designs on 12 elements derived from such a design are established. All of these results depend heavily upon generalizations of block intersection number equations of N. S. Mendelsohn.     

Estimates for k-Hessian operator and some applications

The k-convex functions are the viscosity subsolutions to the fully nonlinear elliptic equations F _k [u] = 0, where F _k [u] is the elementary symmetric function of order k, 1 ? ? 6 n, of the eigenvalues of the Hessian matrix D ² u. For example, F ₁[u] is the Laplacian Δu and F _n [u] is the real Monge-Ampère operator detD ² u, while 1-convex functions and n-convex functions are subharmonic and convex in the classical sense, respectively. In this paper, we establish an approximation theorem for negative k-convex functions, and give several estimates for the mixed k-Hessian operator. Applications of these estimates to the k-Green functions are also established.     

Sufficient conditions for the self-adjointness of the Sturm—Liouville operator

Let L be the minimal operator in L₂(R¹) generated by the expressionly=?y″+q(x)y, Im q(x) ≡ 0, let Δ_k(k=+-1,+-2,...) be a sequence of disjoint intervals going out to +-∞ for k→+=∞, and let δ_k be the length Δ_k. If (ly,y)^≥?γ_k‖y‖² on all smooth y(x) with support in δ_k, wherebyγ _k>0, $$\sum\nolimits_{k = 1}^\infty {(\gamma _k + \delta _k^{ - 2} ) - 1 = } \sum\nolimits_{k = - \infty }^{ - 1} {(\gamma _k + \delta _k^{ - 2} ) - 1 = \infty ,} $$ . then the operator L is self-adjoint. This theorem generalizes criteria for the self-adjointness of L obtained earlier by R. S. Ismagilov, A. Ya. Povzner, and D. B. Sears.