A proof is given here of a theorem of Sarason [9, Theorem 2], the proof being valid in an arbitrary (non-separable) complex Hilbert space. Sarason's proof uses a theorem and lemma of Wermer which may both fail when the separability hypothesis is omitted [3]. By using a special case of Sarason's theorem and another result of Sarason [10, Lemma 1] a simplified and shortened proof is given of a result of Scroggs [11, Corollary 1].

If R is a local (Noetherian) ring, it is well known that R is regular if and only if its completion is regular. It is the purpose of this note to show that a similar result is true for Noether lattices.

Let K be a topological field. On introducing the vector-space topology on the n × n matrices over K, it becomes clear that the determinant map φ enjoys the following properties:

(A) φ is a continuous surjective homomorphism from GLn(K) to K*,

(B) φ(μa) = μn φ(a) for each non-zero φ in K, and all a in GLn(K).

Let γ and γ' be non-negative integers. We say that the graph G is (γ, γ') bi-embeddable if G can be embedded in a surface of genus γ and the complement Ḡ of G can be embedded in a surface of genus γ'. Let N(γ, γ') be the least integer such that every graph with at least N(γ, γ') points is not (γ, γ') bi-embeddable. It has been shown in [1] and [5] that N(0, 0) = 9; this result was also obtained by John R. Ball of the Carnegie Institute of Technology. Our object here is to obtain upper and lower bounds for N(γ, γ').

Let E[τ] be a locally convex Hausdorff topological vector space. An extended decomposition of E[τ] is a family {Ea}α∈A of closed subspaces of E such that, for each x in E and each α in A, there exists a unique point xα in Eα, with Here convergence will have the following meaning. Let Ф denote the set of all finite subsets of A. The sum is said to be convergent to x if for each neighbourhood U of 0 in E, there is an element φ0 of Ф such that , for all φ in Ф containing φ0. It follows that is Cauchy if and only if, for each neighbourhood U of 0 in E, there is an element φ0 of Ф such that , for all φ in Ф disjoint from φ0.

A bounded monotonic sequence is convergent. This paper shows that a bounded sequence which is g-monotonic (to be defined) also converges. The proof generalises one attributed to Professor R. A. Rankin by Copson [1]. The theorem requires two definitions: the first axiomatises the notion of “average“ and the second generalises the concept of monotonicity.

Let be a C*-algebra acting on the Hilbert space H and let be the self-adjoint elements of . The following characterization of commutativity is due to I. Kaplansky (see Dixmier [3, p. 58]).

In [2], H. Delange gives the following characterization of the sine function.

Theorem A. f(x)=sin x is the only infinitely differentiable real-valued function on the real line such that f'(O)= 1 and

for all real x and n = 0,1,2,….

It is clear that, if f satisfies (1), then the analytic continuation of f is an entire function satisfying

for all z in the complex plane. Hence f is of at most order one and type one. In this note, we prove the following theorem.

An (n, q) graph consists of n nodes and q edges, i.e. q distinct unordered pairs of different nodes, so that there are no loops or multiple edges. We write T for the number of unlabelled (n, q) graphs and F for the number of labelled (n, q) graphs. We say that a labelled graph is symmetric if there is a nonidentical permutation of its nodes which leaves the graph unaltered. We write r for the order of the automorphism group of the graph, i.e. the group of all those permutations of the nodes which leave the graph unaltered; we say that the graph is of symmetry order r. A graph which is not symmetric is called asymmetric and, for such a graph, obviously r = 1. We say that an unlabelled graph is symmetric or asymmetric according as the graph obtained by labelling its nodes is symmetric or asymmetric.

Throughout the following note R will denote an associative ring with unit element 1. We shall denote by R-mod [resp. mod-R] the category of all unitary left [resp. right] R-modules. Morphisms in these categories will be written as acting on the side opposite scalar multiplication. All other functions will be written as acting on the left. If is a category, we shall abuse notation and write “A∈ when we mean “A is an object of ”.

A (v, k, λ)-configuration, also called a symmetric balanced incomplete block design, is an arrangement of v distinct objects called points or varieties into v subsets called lines or blocks such that each line contains exactly k points and each pair of distinct lines contains exactly λ points in common. To avoid certain trivial configurations, one assumes that 0<λ<k<v–1.

Let K be a field which contains a primitive nth root of unity w if n is odd and a primitive 2nth root of unity ζ such that ζ2 = w if n is even.

1. Equation (4) should read

2. On p. 83 below equation (7) replace

3. On p. 83 two lines above equation (9) replace

The aim of this note is to generalize to an arbitrary partially ordered set (poset) (P, ≦) the standard lattice results on the Jordan–Dedekind Chain Condition (abbreviated hereafter to J.D.C.C.). Birkhoff [1] defines semimodularity for a lattice L by

(ξ) if x, y cover a and x # y, then x ∨ y covers x and y.

The convergence of least squares approximations for dual orthogonal series in Hilbert space is established, thus providing a theorem applicable to practically all dual orthogonal series (such as dual trigonometric series, dual Bessel series, etc.) that have appeared in the literature. Our results establish for such dual series the existence of a sequence of functions satisfying in the L2norm the dual series relation, with an error tending to zero and, in particular, rigorously justify the calculations in [2] which showed least squares to be a practical approximation procedure for dual trigonometric equations. In fact, the desire to provide a rigorous convergence theorem for [2] motivated this study.

Let C(T) be the Banach algebra of all complex-valued continuous functions on the compact set T of all complex numbers with modulus one. As usual we may suppose that A is embedded in C(T), where A is the disc algebra, i.e., the algebra of all complex-valued functions f(λ) continuous for |λ| ≦ 1. and analytic for |λ| < 1. We set Mλ = {f ∈ A: f(λ) = 0} and Mλ = {f ∈ A: f(λ) ≧ 0}.

The purpose of this note is to provide by means of an example a negative answer to a conjecture of Hajós [3] concerning the factorization of finite abelian groups. This question is also raised as Problem 81 in Fuchs [2].

Let A be a unital normed algebra over the complex field ℂ, A' the dual space of A, i.e., the Banach space of all continuous linear functionals on A, and let S be the set of all states on A, i.e.,