In (2) Lane and Scherk discussed differentiate points of arcs in the conformai (inversive) plane. Arcs A3 of cyclic order three were discussed in (3; 4). In the present note we give necessary and sufficient conditions for the union of two A3's to be an A3 (Theorem 1), and for an A3 to be extensible to a larger one (Theorem 2). The related problem of extending arcs in projective n-space was dealt with by Haupt in (1) and Sauter in (5; 6).

Let Xn denote an n-dimensional differentiate manifold referred to local coordinates xi. An m-dimensional subspace Cm (m < n) of Xn can be represented parametrically in the form

1.1

In this paper we consider two closely related problems concerning a complete locally m-convex (LMC) algebra A with identity. Let a be a fixed element of A, and let P(a) be the smallest closed subalgebra containing a and 1. If B is any subalgebra containing a and 1, we let σ(a; B) denote the spectrum of a as an element of B. (I) Describe the set σ(a; P(a)) in terms of σ(a; A). (II) Give necessary and sufficient conditions in order that σ (a; B) = σ(a; A) for every closed subalgebra B of A which contains a and 1.

Einer Anregung I. Schurs folgend, untersuchte W. Specht bereits in seiner Dissertation (10) Gruppen, die unter den neueren Oberbegriff des Kranzproduktes zweier Gruppen fallen: die sogenannten Symmetrien . Allgemeine Kranzprodukte wurden von ihm in einer nachfolgenden Arbeit (11) behandelt; dort wird deren gewöhnliche Darstellungstheorie in aller Ausführlichkeit angegeben.

Let H be a Hilbert space with the usual product [x, y] and with an indefinite inner product (x, y) which, for some orthogonal decomposition

in H, is defined by

where

and dim H1 = κ, a fixed positive integer.

In recent years elliptic boundary value problems have been studied in great detail; see, for example, Agmon (1), Agmon, Douglis, and Nirenberg (2), Browder (4), Hormander (7), Schechter (10; 11; 12), Agranovich and Dynin (3). In all these cases the boundary problems considered were local or semilocal, i.e. the boundary operators involved are differential operators possibly having singular integral operators for coefficients (cf. (3)).

In the first part of this paper we state and prove a theorem concerning the partition (j; l, i) of an integer j into at most l integers , none of which exceed i; l and i being themselves integers, (j; l, i) is thus the number of distinct solutions of the equations

1.1

where the satisfy the inequalities

1.2

We are concerned here with the question of which finite groups and vector spaces possess subsets which are moved by every non-identity automorphism (in the vector-space case—non-singular linear transformation). We find that this is the case for all but four finite-dimensional vector spaces (2-, 3-, and 4-dimensional space over Z2, 2-dimensional space over Z3), and for all finite groups except for those corresponding to the vector-space exceptions, and the quaternion group of order eight. The question was first posed to the authors, in the vector-space case, by Morris Marx.

Let F be a vector space of dimension two, three, or four over a field of characteristic not two, and let V have a non-singular orthogonal metric. The problem discussed in this paper is the determination of all finite groups that can occur as subgroups of the rotation group of V.

The stability of the solutions of an ordinary differential equation will be discussed here. The purpose of this note is to compare the stability results which are valid with respect to a compact set and the stability results valid with respect to an unbounded set. The stability of sets is a generalization of stability in the sense of Liapunov and has been discussed by LaSalle (5; 6), LaSalle and Lefschetz (7, p. 58), and Yoshizawa (8; 9; 10).

Let X = (X, p) be a seminormed complex linear space with zero θ. Natural definitions of convergent sequence, Cauchy sequence, absolutely convergent series, etc., can be given in terms of the seminorm p. Let us write C = C(X) for the set of all convergent sequences for the set of Cauchy sequences; and L∞ for the set of all bounded sequences.

For a positive integer, p, a strictly increasing unbounded sequence of positive numbers {λn: n ⩾ 1} and an arbitrary sequence of complex numbers {an} let

1

2

Let Mm(F) be the vector space of m-square matrices X — (Xij), i,j= 1, … , m over a field ƒ;ƒ a function on Mm(F) to some set R. It is of interest to determine the structure of the linear maps T: Mm(F) → Mm(F) that preserve the values of the function ƒ (i.e., ƒ(T(x)) — ƒ(x) for all X). For example, if we take ƒ(x) to be the rank of X, we are asking for a determination of the types of linear operations on matrices that preserve rank (6). Other classical invariants that may be taken for ƒ are the determinant, the set of eigenvalues, and the rth elementary symmetric function of the eigenvalues.

In this paper we follow the notation of (2). In (5), Luce showed, in other terminology, that if d is the diameter of a strongly connected digraph, D, on n vertices with m edges, then

1.1

this inequality being sharp; from (1.1) one may immediately derive sharp upper bounds for d in terms of m and n, this being a generalization of the obvious and well-known inequality

1.2

In this note, we are concerned with the following generalization of a wellknown theorem of M. H. Stone; see (2, 8.2).

Theorem 1. Let L be a relatively complemented distributive lattice.

(I) If L has no least element, then L is isomorphic to the lattice of non-empty compact-open subsets of an anti-Hausdorff, nearly-Hausdorff, T1-space with a base of open sets consisting of compact-open sets.

(II) (3, Theorem 1) If L has a least element, then L is isomorphic to the lattice of all compact-open subsets of a locally compact totally disconnected space. Moreover, the spaces of (I) and (II) are compact if and only if L has a greatest element.

The space in question is the space of prime ideals of L with the hull-kernel topology.

The author is indebted to M. G. Stanley for several conversations concerning this note.

In this paper, all spaces will have the homotopy type of simply connected CW-complexes, and will have base points which are preserved by maps and homotopies. We denote by [X, Y] the set of homotopy classes of maps from X to Y, and by N[X, Y] the subset of those homotopy classes [ƒ] which induce the zero homomorphism on homotopy, that is, is the zero homomorphism for each i.

The main result of this paper is the following.

Theorem 1. Let A be a simple, commutative, finite-dimensional algebra containing an idempotent over a field of characteristic 0, and let the algebra A' obtained from A by adjoining a unity element satisfy an identity of degree ≦ 4 not implied by commutativity. Then either A is a Jordan algebra or A is two-dimensional over an appropriate field E.

Our present work is divided into three sections. In §2 we study the metrizability of spaces with a Gδ-diagonal (see Definition 2.1). In §3 we study the metrization of topological spaces by means of collections of (not necessarily continuous) real-valued functions on a topological space. Our efforts, in §§2 and 3, are directed toward answering the following question: “Is every normal, metacompact (see Definition 2.4) Moore space a metrizable space?” which still remains unsolved. (However, Theorems 2.12 through 2.15 and Theorem 3.1 may be helpful in answering the preceding question.) In §4 we prove an apparently new necessary and sufficient condition for the metrizability of the Stone-Čech compactification of a metrizable space and hence for the compactness of a metric space.

In (3), J. Hartmanis raised the question whether the lattice of all topologies in a given set is complemented and gave the affirmative answer for the case of a finite set. H. Gaifman (2), has extended this result to denumerable sets. Using Gaifman's paper, Anne K. Steiner (4) has proved that the lattice is always complemented. Our aim in this article is to give an alternative proof, independent of Gaifman's results. So far, Steiner's proof has not been available to the author.

The aim of this paper is to present a unified treatment of certain theorems in Combinatorial Analysis (particularly in enumerative graph theory), and their relations to various results concerning symmetric functions and the characters of the symmetric groups. In particular, it treats of the simplification that is achieved by working with S-functions in preference to other symmetric functions when dealing with combinatorial problems. In this way it helps to draw closer together the two subjects of Combinatorial Analysis and the theory of Finite Groups. The paper is mainly expository; it contains little that is really new, though it displays several old results in a new setting.