Let $E$ be a rearrangement invariant (r.i.) function space on ‘0, 1’. We consider the space $\Lambda({\cal R},E)$ of measurable functions $f$ such that $fg \in E$ for every a.e. converging series $g =\sum a_nr_n \in E$, where $(r_n)$ are the Rademacher functions. Curbera ‘4’ showed that, for a broad class of spaces $E$, the space $\Lambda({\cal R},E)$ is not order-isomorphic to a r.i. space. We study cases when $\Lambda({\cal R},E)$ is order-isomorphic to a r.i. space. We give conditions on $E$ so that $\Lambda({\cal R},E)$ is order-isomorphic to $L_{\infty}$. This includes certain classes of Lorentz and Marcinkiewicz spaces. We study further when $\Lambda({\cal R},E)$ is orderisomorphic to a r.i. space different from $L_{\infty}$. This occurs for the Orlicz spaces $E = L_{\Phi_q}$ with $\Phi_q(t)$ asymptotically equivalent to $\exp |t|^q-1$ and $0 < q < 2$.

For a given function f, regular in the unit disk D(0, 1), logarithmic means of order p may be defined in terms of integrals by the formulae

for 0 < p < , and by

when 0 < r < 1. Associated p-orders are subsequently defined by

for 0 < p.

The ringoids discussed in the preceding paper of this series(3) are characterized by two axioms which permit the operations of an exact category to be carried out within the structure of the ringoid. These operations do not in general include the formation of direct sums or products, for which new axioms are required. For a finite number of constituents these axioms are equivalent to the corresponding axiom in Buchsbaum's paper(1).

Let G be a finite group, p a prime divisor of |G| and suppose that G is not a p-group. In this note, we show that the number of elements x ∈ G such that xp = 1 is at most (p|G|)/(p + 1). This answers a question posed by D. MacHale. When G is a Frobenius group of order p(p + 1), p a Mersenne prime, the above bound is attained.

Let (Ω, Σ, P) be a probability space and suppose that all random variables are defined on this space.

Let F be a non-cyclic free group, R a normal subgroup of F and G = F/R, i.e.

where π is the natural projection of F onto G, is a free presentation of G. Let R′ denote the commutator subgroup of R. The quotient F/[R′,F] is a free central extension

of the group F/R′, the latter being a free abelianized extension of G. While F/R′ is torsion-free (see, e.g. [2], p. 23), elements of finite order may occur in R′/[R′,F], the kernel of the free central extension (l·2). Since C. K. Gupta [1] discovered elements of order 2 in the free centre-by-metabelian group F/[F″,F] (i.e. (1·2) in the case R = F′), torsion in F/[R′,F] has been studied by a number of authors (see, e.g. [4–13]). Clearly the elements of finite order in F/[R′,F] form a subgroup T of the abelian group R′/[R′,F]. It will be convenient to write T additively. By a result of Kuz'min [5], any element of T has order 2 or 4. Moreover, it was pointed out in [5] that elements of order 4 may really occur. On the other hand, it has been shown in [11] that, if G has no 2-torsion, then T is an elementary abelian 2-group isomorphic to H4(G, ℤ2). So if T contains an element of order 4, then G must have 2-torsion. We also mention a result of Zerck [13], who proved that 2T is an invariant of G, i.e. it does not depend on the particular choice of the free presentation (1·1).

An (n, q) graph consists of n labelled nodes and q edges, i.e. unordered pairs of different nodes. The maximum possible value of q is N = ½n(n − 1) and the (n, N) graph is the complete graph. We write B(h, k) = h!/{k!(h − k)!}. The number of (n, q) graphs is clearly B(N, q). A k-cycle in a graph consists of a sequence

of k edges, where D1D2,…, Dk are all different nodes. We are concerned here with the probability P = P(n, q, k) that a k-cycle will be present in an (n, q) graph, that is, the proportion of all (n, q) graphs which contain at least one k-cycle. We investigate the limit of P as n → ∞ and in particular try to determine when P → 1 (when we say that almost all (n, q) graphs contain a k-cycle) and when P → 0 (when we say that almost no (n, q) graphs contain a k-cycle).

Let $X\,{=}\,\{X(t), \ t \in {\R^N}\}$ be a multiparameter fractional Brownian motion of index $\alpha$ ($0< \alpha < 1$) in $\R^d.$ We prove that if $N < \alpha d\ $, then there exist positive finite constants $K_1$ and $K_2 $ such that with probability 1, $$ K_1 \le \hbox{$\varphi$-$p(X([0,1]^N))$} \,{\le} \hbox{ $\varphi$-$p({\rm Gr}X([0,1]^N))$} \,{\le}\, K_2$$ where $\varphi(s) = s^{N/\alpha}/(\log \log1/s)^{N/(2 \alpha)}$, $\varphi$-$p(E)$ is the $\varphi$-packing measure of $E$, $X([0, 1]^N)$ is the image and ${\rm Gr}X([0, 1]^N) \,{=}\, \{(t, X(t)); \ t \in [0, 1]^N\}$ is the graph of $X$, respectively. We also establish liminf and limsup type laws of the iterated logarithm for the sojourn measure of $X$.

The notion of almost alternating links was introduced by C. Adams et al ([1]). We give a sufficient condition for an almost alternating link diagram to represent a non-splittable link. This solves a question asked in [1, 3]. A partial solution for special almost alternating links has been obtained by M. Hirasawa ([5]). As an application, Theorem 2.2 gives us a simple finite algorithm to decide if a given almost alternating link diagram represents a splittable link without increasing the number of crossings of diagrams in the process. Moreover, we show that almost alternating links with more than two components are non-trivial. In Section 2, we state these results in detail. To prove our theorem, we use a technique invented by W. Menasco (see [6, 7]), this is reviewed in Section 3. We also apply “the charge and discharge method” to our graph-theoretic argument, which was used to prove the four color theorem in [4], we explain this in Section 4.

For a polyhedral domain , and a Hilbert metric nonexpansive map T:Σ→Σ which does not have a fixed point in Σ, we prove that the omega limit set ω(x;T) of any point x ∈ Σ is contained in a convex subset of the boundary ∂Σ. We also identify a class of order-preserving homogeneous of degree one maps on the interior of the standard cone which demonstrate that there are Hilbert metric nonexpansive maps on an open simplex with omega limit sets that can contain any convex subset of the boundary.

Let us consider an experiment, the possible outcomes of which are random events. Let A1, A2, …, An be some of these outcomes. Define the random variable ηn as the number of the events occurring simultaneously among the A1, A2, …, An in an experiment. Denote by Pk = (ηn = k) (k = 0,1, 2, …, n), the distribution of the random variable ηn and by , the binomial moments of ηn. Here is the symbol of the probability and & that of the expectation.

1. Introduction. It is well known that every finite-dimensional irreducible representation of a nilpotent group over an algebraically closed field is monomial, that is induced from a 1-dimensional representation of some subgroup. However, even a finitely generated nilpotent group in general has infinite-dimensional irreducible representations, and as a first step towards an understanding of these one wants to discover whether they too are necessarily monomial. The main point of this note is to show how far they can fail to be so.

The main aim of this paper is to present a general method of proving Ω-estimates for a class of arithmetic error terms. We assume that error terms in question are boundary values of harmonic functions on the upper half-plane satisfying certain subsidiary conditions. We prove a general theorem for an axiomatically defined class of such functions and then we show how this result can be used to give statements in concrete situations. As examples we treat the classical case of the remainder term in the prime number formula obtaining a new proof of the well-known result of J. E. Littlewood, and the case of the remainder term in the asymptotic formula for the summatory function of the square-free divisor function. In the latter case our result is new.

The general multipole solutions obeying the appropriate boundary conditions are presented for stationary non-axisymmetric electromagnetic fields in the Kerr background geometry.

1. Introduction. Let kG denote the group algebra of a group G over a field k. In this paper we are first concerned with the zero divisor conjecture: that if G is torsion free, then kG is a domain. Recently, K. A. Brown made a remarkable breakthrough when he settled the conjecture for char k = 0 and G abelian by finite (2). In a beautiful paper written shortly afterwards, D. Farkas and R. Snider extended this result to give an affirmative answer to the conjecture for char k = 0 and G polycyclic by finite. Their methods, however, were less successful when k had prime characteristic. We use the techniques of (4) and (7) to prove the following:

Theorem A. If G is a torsion free abelian by locally finite by supersoluble group and k is any field, then kG is a domain.

In a previous paper of the same title (1) on

where e(t) is even and has least period 2π, I have shown that the equation has a family of periodic solutions or, equivalently, that a topological transformation T has a family of fixed points. Since much of the detail in (1) is irrelevant here, it will be convenient if the results we must quote about are put into the following form:

Theoerm A. There is a constant integer p such that, whenever k ≥ p, there is at least one solution xk(t) of (1·1) for which

(i) xk(0) > 0, ẋk(0) = 0 and xk(t) has period 2π;

(ii) xk(t) = xk(2π–t);

(iii) xk(t) has, in 0 ≤ t < 2π, k positive maxima, k negative minima and no other stationary points;

(iv)

This except (ii), is a special case of Theorem 2 with the notation x*(t|k, 1, 0) simplified to xk(t) and the constant p introduced to guarantee that (vi) of Theorem 2 implies (iv) above. Finally Lemma 1 of (1), in its original form or as specialized in Theorem B (i) below, gives (ii).

We shall write ak = xk(0) and note, though we do not need to use it here, that, by (v) of Theorem 2, ak = kw + O(k−2) as k→ ∞. If Fk denotes the point (ak, 0) of the (a, b)-plane then Fk is a fixed point of T and we can best state this paper's results in terms of the segment joining a pair of such points.

An asymptotic expression is found for the lift distribution on a long, narrow, laminar wing, at incidence in a supersonic stream. The approximations of the linearized potential theory are used.

In this paper, we study the residual Julia sets of meromorphic functions. In fact, we prove that if a meromorphic function $f$ belongs to the class ${\bf S}$ and its Julia set is locally connected, then the residual Julia set of $f$ is empty if and only if its Fatou set $F(f)$ has a completely invariant component or consists of only two components. We also show that if $f$ is a meromorphic function which is not of the form $\alpha + (z\,-\,\alpha)^{-k}e^{g(z)}$, where $k$ is a natural number, $\alpha$ is a complex number and $g$ is an entire function, then $f$ has buried components provided that $f$ has no completely invariant components and its Julia set $J(f)$ is disconnected. Moreover, if $F(f)$ has an infinitely connected component, then the singleton buried components are dense in $J(f)$. This generalizes a result of Baker and Domínguez. Finally, we give some examples of meromorphic functions with buried points but without any buried components.

Consider the integral

where x1, x2, …, xN are jointly distributed in a multivariate normal distribution f(x1, x2, …, xN) with (pij) as the correlation matrix. The integral has been expressed in an infinite series of tetrachoric functions for N≥2. The infinite series is not only complicated, but also is very slowly convergent and is consequently not of much practical use. Plackett (8) obtains a reduction formula for expressing normal integrals in four variates as a finite sum of single integrals of tabulated functions. These integrals have then to be evaluated by a rather awkward numerical quadrature.

In 1933 Borsuk(2) made the following conjecture: Every bounded set of points in Euclidean n-space En can be represented as the union of n + 1 sets of smaller diameter. He proved it for n = 2. Hadwiger (5) proved Borsuk's conjecture assuming the additional condition that the surface of the set is sufficiently smooth. On the other hand, up to now the conjecture has been proved for n ≤ 3 only (3, 4).