Ordered partitions are enumerated by Fn = Σk k !S(n, k) where S(n, k) is the Stirling number of the second kind. We give some comments on several papers dealing with ordered partitions and turn then to ordered Fibonacci partitions of {1, ߪ, n}: If d is a fixed integer, the sets A appearing in the partition have to fulfill i, j ∈ A, i ≠ j ⟹ |i-j| ≥ d. The number of ordered Fibonacci partitions is determined.

The behaviour of summability transforms of power series outside their circles of convergence has been studied by many authors. In the case of the geometric series Luh [6] and Tomm [10] showed that there exist regular methods A which provide an analytic continuation into any given simply connected region G that contains the unit disc but not the point 1. Moreover, the Atransforms of the geometric series may be required to converge to any chosen analytic function on prescribed regions outside the unit circle. In this paper, these results are extended to power series representing other meromorphic functions. It is also shown that the summability methods involved may be chosen to be generalized weighted means previously introduced by Faulstich [1].

Let E be a Banach lattice,

where x1, …, xn ∊ E. We study properties of constants

A characterization of AM-spaces is obtained which generalizes the result of Abramocič, Positselskiĭ, Yanovskii. Asymptotic estimates of φp for some classical finite dimensional lattices are given.

It is known that if a topological property of Tychonoff spaces is closed-hereditary, productive and possessed by all compact Hausdorff spaces, then each (0-dimensional) Tychonoff space X is a dense subspace of a (0-dimensional) Tychonoff space with such that each continuous map from X to a (0-dimensional) Tychonoff space with admits a continuous extension over . In response to Broverman's question [Canad. Math. Bull. 19 (1), (1976), 13–19], we prove that if for every two 0-dimensional Tychonoff spaces X and Y, if and only if , then is contained in countable compactness.

Let n ≥3 and m≥3 be integers. Let Kn be the cyclotomic field obtained by adjoining a primitive nth root of unity to the field of rational numbers. Let denote the maximal real subfield of Kn. Let hn (resp., ) denote the class number of Kn (resp., ). For fixed m we show that m divides hn and hn for asymptotically almost all n. Also for those Kn and with a given number of ramified primes, we obtain lower bounds for certain types of densities for m dividing hn and .

Let X be a separable metric space and let be a family of countably many self-maps of X. Then there is a countable subalgebra of the Boolean algebra of regular open subsets of X which is a base for X such that for each the function defined by Φf(B) = (f-1(B))-0 is a homomorphism.

Questions concerning the convergence of Padé and best rational approximations are considered from a categorical point of view in the complete metric space of entire functions. The set of functions for which a subsequence of the mth row of the Padé table converges uniformly on compact subsets of the complex plane is shown to be residual.

The speed of convergence of best uniform rational approximations and Padé approximations on the unit disc is compared. It is shown that, in a categorical sense, it is expected that subsequences of these approximants will converge at the same rate.

Likewise, it is expected that the poles of certain sequences of best uniform rational approximations wil be dense in the entire plane.

We are concerned with coefficient estimates, and other similar problems, of the typically real functions and of the functions with positive real part. Following the stream of ideas in [1], new results and generalizations of others given in [1], [2] and [3] are obtained.

The classical Levi problem in several complex variables characterizes domains of holomorphy in terms of a boundary condition called pseudo convexity. The purpose of this note is to give a characterization of those domains D in ℂ×ℝ, where one can always solve the -problem with C∞ parameters, in terms of a certain kind of convexity condition on their boundaries.

A completely regular HausdorfT space is extra countably compact if every infinite subset of βX has an accumulation point in X. It is a theorem of Comfort and Waiveris that if X either an F-space or realcompact (topologically complete), then there is a set {Pξ:ξ<2C} of extra countably compact (countably compact) subspaces of αX such that Pξ ∩ Pξ = X, for ξ<ξ'<2C. Comfort and Waiveris conjecture that in all three cases, the spaces may be chosen pairwise non-homeomorphic. We prove this conjecture, using D- limits and weak P-points. We also give a partial solution to another question asked by Comfort and Waiveris.

Soit GLn (υ) le groupe des matrices inversibles n × n sur υ et soit SLn (υ) le groupe des matrices n × n de déterminant 1 sur υ. Lorsque υ est un anneau local avec idéal maximal p, W. Klingenberg (Amer. J. Math. 1961) a classifié les sous-groupes normaux de GLn(υ) et de SLn(υ) au moyen de certains groupes de congruences déterminés par les idéaux de o, sauf lorsque n = 2 et 2 ∊ p ou υ/p = 𝔽3. Ces cas furent étudiés par N. H. J. Lacroix (Can. J. Math. 1969) qui trouva (lorsque υ/p≠𝔽2) la même classification pour les sous-groupes normaux de GL2(υ) ; sa méthode donne simultanément la même classification également pour les sous-groupes normaux de SL2(υ) si l'anneau o satisfait à une forte condition appelée Propriété T.

Au cours de cette note, nous précisons que les sous-groupes normaux de SL2(υ) obéissent à la classification de Klingenberg si et seulement si υ a la Propriété T. Par la suite nous montrons qu'en l'absence de cette condition, l'on n'a pas de vraie classification basée sur les transvections. Divers résultats sur les sous-groupes normaux illustrent ce qu'on peut attendre d'une entreprise visant à décrire les sous-groupes normaux de SL2(υ) en l'absence de la Propriété T.

This paper deals with the differential equation: ẍ + μF(ẋ) + x = ƒ( X, ẋ, t/Tμ) for μ ≫ 1 where F is a piecewise linear function and f is a periodic function of period μT, where T is to be chosen. It is established that periodic forced vibrations exist in an annular domain R(μ) constructed for the free vibration (ƒ ≡ 0), provided ƒ is not of higher order than Subsequently with ƒ = A cos (2πt/μT*), an asymptotic treatment of the forced vibration problem is carried out, by finding the proper initial conditions and the proper period μT* of f. Finally it is concluded that μT* is close to the period of the free vibration.

G. B. Gurevič enumerated all the orbits of GL8(ℂ) in Λ3(ℂ8). There are precisely 23 orbits (including the trivial orbit). For each of these orbits, we determine its closure (for the ordinary topology).

This note contains a strengthened version of the following well-known theorem: there exists a continuous function whose Fourier series diverges at a point.

Jackson type theorems are obtained for the comonotone approximation of piecewise monotone functions by polynomials.

Erdös has defined g(n) as the smallest integer such that any set of g(n) points in the plane, no three collinear, contains the vertex set of a convex n-gon whose interior contains no point of this set. Arbitrarily large sets containing no empty convex 7-gon are constructed, showing that g(n) does not exist for n≥l. Whether g(6) exists is unknown.

Let R be an integral domain with quotient field K and let I be a nonzero ideal of R. We show (1) that I is invertible if and only if for every nonempty collection {Bα} of ideals of R and (2) that I is flat if and only if I(B ∩ C) = IB∩IC for each pair of ideals B and C of R.

Let d(G) denote the minimal number of generators of the finite p-group G, r(G) the maximum over all subgroups H of G of d(H) and ra(G) the maximum over all abelian subgroups H of G of d(H). If G is of class two it is clear that

By considering properties of the stability number of graphs we construct examples which show that any value of r(G) within these bounds can occur.

Let

It is proved that the function f reaches its maximum for n = 6 983 776 800, and that maxn≥2f(n) = 1.5379. The proof deals with superior highly composite numbers introduced by Ramanujan.

In this note we obtain a q-analog of a pair of biorthogonal sets of rational functions which have been obtained recently by M. Rahman in connection with the addition theorem for the Hahn polynomials.