A topological semiring is a system (S, +, ·) where (S, +) and (S, ·) are topological semigroups and · distributes across + as in a ring; that is, for all x, y, z in S, The operations + and · are called addition and multiplication respectively.

Let E, Ê, and E′ denote a locally convex linear Hausdorff space, completion of E and the dual of E, respectively. It has been observed that Ê is a subspace of E″ under certain conditions on E. It is the primary goal of this paper to give necessary and sufficient conditions for the Ê ⊂ E″ to be valid. Such conditions are found and are given Theorem 4. With a variation of the technique used, several equivalent characterizations of semi-reflexive spaces are given in Theorem 5. The nationa throughtout will follow that in [2].

In [1], it was shown that if ƒ ∈ Lp(Rn), where 1 < p < ∞, then the closed subspace of Lp (Rn) spanned by functions of the form [where a1, …, an, b1, …, bn, are real numbers; ak, ≠ 0; k = 1, …, n] coincides with the whole of Lp(Rn). In the present note, analogous results are derived for the spaces of integrable functions, essentially bounded measurable functions, bounded continuous functions, and continuous functions vanishing at infinity.

The aim of this paper is, briefly, an axiomatization of relativistic kinematics. Before stating the aims in more precise terms, a few words about the origins of the paper will be necessary. The idea of a revision of the axiomatic foundations of relativistic kinematics came up in discussions with the late M. L. Urquhart at the 1963 (3rd) Summer Research Institute of the Australian Mathematical Society, and it was a suggestion by Urquhart which started off the present investigation. Following his suggestion I prepared a preliminary draft containing the outlines of an axiomatic system for Minkowski space-time and passed it on to him. Shortly before his death Urquhart asked Professor D. Elliott to send the manuscript back to me and it was this manuscript which formed the nucleus of the present paper.

The Ritz method reduces eigenvalue problems involving linear operators on infinite dimensional spaces to finite matrix eigenvalue problems. This paper shows that for a certain class of linear operators it is possible to choose the coordinate functions so that numerical solution of the matrix equations is considerably simplified, especially when the matrices are large. The method is applied to the problem of overtone pulsations of stars.

A study is made of the aerodynamic damping in a cascade of oscillating aerofoils in subsonic compressible flow with the system mode described by a constant interblade phasing predicted by Lane (9). The integral downwash equation is obtained as an extension of Possio's equation for an isolated aerofoil. Procedures for a practical solution of the equation have allowed the aerodynamic reactions and damping derivatives to be evaluated with a digital computer after minimisation of the critical flutter velocity with respect to interbiade phase angle. The effect of aerodynamic lag in separation conditions as a function of reduced frequency and chordwise location is compared with results without separation.

If we consider any particular topological semigroup S it may seem reasonable to ask for a characterization of all additions on S which make it a topological semiring. We are interested here in this problem when

(i) S is an (I)-semigroup;

(ii) S is [0, ∞) and the multiplication on S is such that 0 and 1 are Zero and identity respectively.

Let Xi, i = 1,2,3,… be a sequence of independent and identically distributed random variables and write S0 = 0, Sn = ∑ni=1Xi, n ≧ 1. Let In(0), In(1), …, In (n) be that unique permutaion of 1, 2, …, n such that SIn(0) ≦ SIn(1) ≦ … ≦ SIn(n) and such that if Si = Sk with i < k then In(k) < In(j). Thus, In(j) is an index of the j-th largest partial sum.

Let M1 and M2 be two sets of probability measures defined on Rn. Ameasurable R1 valued function h (l ≧1) is said to distinguish M1from M2unbiasedly if there are numbers or vectors I1 and I2 (I1≠I2) such that ∫Rnh(x)m(dx) = Ii if m is in Mi (i = 1, 2). Here we shall be concerned with the case where M1 and M2 are translation families, in that all of the elements of Mi are translates of a single measure mi. This means that if, for any t in Rn, mtt is the measure defined by , where E−t {x−t: x ∈ E}, then Mi = , where T is a subset of Rn. If M1 and M2 are of this type, we will investigate the conditions under which there does not exist a function to distinguishing M1 from M2 unbiasedly. A case of special interest arises if m2(E) = m1(BE) = m1 with B a non-degenerate n × n matrix, and particularly a nonzero multiple (scale parameter) of the identity matrix, cf. [1], [2]. For simplicity, take l = 1.

Let ℜk be the variety of all nilpotent groups of class at most k. The purpose of this note is to prove the following Theorem 1. Letbe a variety of groups containing ℜ2, let A and B be torsion-free abelian hopfian groups and let P be the free-product2 of A and B. If P is residually torsion-free nilpotent, then P is hopfian.

No general rule for determining the number N(n) of topologies definable for a finite set of cardinal n is known. In this note we relate N(n) to a function Ft(r1,…, rt+1) defined below which has a simple combinatorial interpretation. This relationship seems useful for the study of N (n). In particular this can be used to calculate N(n) for small values. For n 3, 4, 5, 6 we find N(3) = 29, N(4) = 355, N(5) = 7,181, N(6) = 145,807.

To assess the mathematical work of the late M. L. Urquhart is, paradoxically, both easy and extremely difficult. It is easy, in that he never published a mathematical paper in any of the journals. Thus one does not have to read a large volume of published work. On the other hand, Urquhart was far from being mathematically inactive, but he communicated his ideas verbally to his associates. At this point of time it is well nigh impossible to recall all the ideas that he discussed so freely during his lifetime. Conversations have long since been forgotten and ideas are now only vaguely remembered. Consequently any objective assessment of Urquhart's mathematical work is very difficult.

The concept of a compactly generated lattice has been studied extensively in connection with decomposition theory (see [1]). This paper investigates the order topology in a lattice which is, along with its dual, compactly generated (hence, bicompactly generated). We show that order convergence is topological and that the order topology is Hausdorff, totally disconnected, and has an open subbase of ideals and dual ideals in any bicompactly generated lattice; furthermore, with an additional restriction, the lattice operations are continuous in the order topology. Next we consider the order topology in certain special types of compactly generated lattices, namely atomic Boolean algebras and sub-complete lattices of atomic Boolean algebras in the former structures the order topology is uniformizable, in the latter, compact.

Let α be an arbitrary positive number. For every integer n ≦ 0 we can write where is the largest integer not greater than, i.e the integral part of, and rn is its fractional part and so satisfies the inequality

We shall consider the following mathematical model of dams of finite capacity. In the time interval (0, ∞) water is flowing into a dam (reservoir). Denote by χ(u) the total quantity of water flowing into the dam in the time interval (0, u). The capacity of the dam is a finite positive number h. If the dam becomes full, the excess water overflows. Denote by δ(u) the total quantity of water demanded in the time interval (0, u). If there is enough water in the reservoir the demand is satisfied, if there is not enough water the difference is supplied from elsewhere Denote by η(t) the content of the dam at time t. η(0) is the initial content.

Some further numerical results are obtained for plane waves propagated into elastic and plastic solids. Quantitative agreement with experimental results indicates that rate of strain effects are not significant.

In this paper a denotes a square matrix with real or complex elements (though the theorems and their proofs are valid in any Banach algebra). Its spectral radius p(a) is given by with any matrix norm (see [4], p. 183). If p(a) < 1 and n is a positive integer then the binomial series converges and its sum satisfies S(a)n = (1−a)−1. Let where q is any integer exceeding 1. Then u(a) is the sum of the first q terms of the series (2). Write and let a0, a1, a2,…be the sequence of matrices obtained by the iterative procedure Defining polynomials φ0(x), φ1(x), φ2(x),…inductively by we have aν = φν (a) and therefore aμaν = aνaμ for all 4 μ, ν. The following is proved in section 2: Theorem 1. If ρ(a) < 1 thenconverges and P(a) = S(a). Furthermore, if p(a) < r < 1, thenfor all ν, where M depends on r and a but is independent of ν and q.

The resemblance of the Goursat problem for the hyperbolic partial differential equations to the initial value problem for the ordinary differential equations has suggested the extension of many well known numerical methods existing for (1.2) to the numerical treatment of (1.1). Day [2] discusses the quadrature methods while Diaz [3] generalizes the simple Euler-method. Moore [6] gives an analogue to the fourth order Runge-Kutta-method and Tornig [7] generalizes the explicit and implicit Adams-methods.