The Scott Conjecture, proven by Bestvina and Handel [2] says that an automorphism of a free group of rank n has fixed subgroup of rank at most n. We characterise in Theorem A below those automorphisms that realise this maximum. It follows from this characterisation, for example, that any such automorphism has linear growth. In our paper [3], we generalised the Scott Conjecture to arbitrary free products, using Kuros rank (see Section 2 below) in place of free rank; in Theorem B, we characterise those automorphisms of a free product realising the maximum. We show that in this case the growth rate is also linear. These results extend those of [4].

In this paper I give a direct proof of a new expansion of the Whittaker function M(a; b; x) as a series of Bessel functions, and some generalizations of this result for the functions 2F2(x) and 4F4(x).

In this paper we discuss homogeneous Diophantine approximation of points on smooth manifolds M in ℝk. We begin with a brief survey of the notation and results. For any x,y ∈ℝk, let

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We give a method for obtaining infinitely many framed knots which represent a diffeomorphic 4-manifold. We also study a relationship between the n-shake genus and the 4-ball genus of a knot. Furthermore we give a construction of homotopy 4-spheres from a slice knot with unknotting number one.

Let E/F be a finite normal extension of number fields with Galois group G. For each virtual character χ of G, denote by L(s, χ) = L(s, χ, F) the Artin L-series attached to χ. It is defined for Re (s) > 1 by an Euler product which is absolutely convergent, making it holomorphic in this half plane. Artin's holomorphy conjecture asserts that, if χ is a character, L(s, χ) has a continuation to the entire s-plane, analytic except possibly for-a pole at s = 1 of multiplicity equal to 〈χ, 1〉, where 1 denotes the trivial character. A well-known group-theoretic result of Brauer implies that L(s, χ) has a meromorphic continuation for all s.

In the course of an investigation of the β-ray spectrum of Ra (B + C) by the ionisation method, Chadwick(1) concluded that the line spectrum is superimposed on a strong continuous background. The ionisation method, however, is not one which admits of high resolving power, and doubts have been entertained whether the continuous spectrum has in fact any real existence. In this connection the case of Ra E is one of special importance, since no line spectrum from this body has been detected by the more sensitive photographic method. Experiments have therefore been undertaken with the object of determining the distribution with velocity of the numbers of particles in the β-ray spectrum of Ra E.

Multitype Moran sets are introduced in this paper. They appear naturally in the study of the structure of the quasi-crystal spectrum, and they generalize some known fractal structures such as self-similar sets, graph-direct sets and Moran sets. It is known that for any Moran set E with a bounded condition on contracting ratios, one has \[\dim_H E=s_*\le s^*=\dim_P E=\dimB E,\] where $s_*$ and $s^*$ are the lower and upper pre-dimension according to the natural coverings. For any multitype Moran set E with a bounded condition on contracting ratios, we prove $\dimB E{=}s^*$. With an additional assumption of primitivity, we prove that for multitype Moran sets, the above formula still holds. We also give some examples to show that if the condition of primitivity is not fulfilled, then it may happen that $\dim_H E<s_*$ or $\dim_P E<s^*$.

One of the inequalities recently found by Cochran and Lee([1], theorem 1) is the following.

If γ and p are real numbers with p > 0, and f(t) is measurable and non-negative on (0, ∞), then

The theory of twist maps is applied to prove the existence of many harmonic and sub-harmonic solutions for certain Newtonian systems of differential equations. The method of proof leads to very precise information on the oscillatory properties of these solutions.

René Thom(5) has shown that if the state of a system is determined by the local minimization of a potential – that is, if the system is so highly dissipative that transients can safely be ignored–then, though a smooth change in the potential function may give rise to a discontinuous change of state, the ways in which this can happen are quite limited. Infact, if we have at most a four-parameter family of potentials, discontinuities of this kind can occur in only seven ways up to local diffeotype, if they are to be structurally stable. (This latter condition is the requirement that it be im-possible to alter the discontinuity type by an arbitrarily small perturbation of the family of potentials: roughly it requires that the behaviour of the system, considered as a function of possible families ofpotentials, be ‘continuous’ at the family concerned. It bears the same relationship as does continuity to computability: a computer given approximately correct data for which to compute the value of a function or the behaviour of a system will give an approximately correct answer if the function is continuous, the system structurally stable. If not, only analytic methods will serve, and the physical significance of the result will be dubious. Fortunately, in the dimensions with which we are concerned, structural stability is an open dense property in the space of possible families of potentials; thus unstable systems can be ignored for almost all purposes, just as we ignore the ‘possibility’ of balancing a pin on its point.)

1. In 1894 Humbert encountered a twisted curve C7, of order 7 and genus 5, the locus of points of contact of tangents from a fixed point N0 to those twisted cubics which pass through five fixed points N1, N2, N3, N4, N5. The cubics of this family which touch an arbitrary plane do so at points on a conic, and it was by investigating this complex of conics that Humbert was led to study C7.

This paper is designed to pave the way for the author's work on the symplectic bordism ring MSp*(12), (13). We here discuss all the notation used, and collect together all the theorems quoted therein. At the same time, I hope that some of the results presented here might be of interest in their own right. Our central theme is the study of the hurewicz map e: S*(X) → E*(X), both in general and certain specific cases.

The method of steepest descents for finding the asymptotic expansion of contour integrals of the form ∫ g(z) exp (Nf(z)) dz where N is a real parameter tending to + ∞ is familiar. As is well known, the principal contributions to the asymptotic expansion come from certain critical points; the most important are saddle-points where df/dz = 0. The original contour is deformed into an equivalent contour consisting of paths of steepest descent through certain saddle-points, the relevant saddle-points. The determination of these is a global problem which can be solved explicitly only in simple cases. The function f (z) may also depend on parameters. The position of the saddle-points depends on the parameters and at a certain set of values of the parameters it may happen that two or more saddle-points coincide. The ordinary expansion is then non-uniform, but appropriate uniform expansions have been shown to exist in earlier work.

The paper describes the results obtained from a study of the bombardment of gold with deuterons of energy up to 9·1 M.e.V. The reactions found to take place in gold are the formation of 2·7 day Au198 by a (d-p) process and of 32 hr. Hg198* in a metastable state by a (d-n) process. The β-ray and γ-ray energies associated with each radioactivity have been measured by absorption methods. Excitation functions for the two reactions have been determined and the results have been compared with those to be expected on theoretical grounds.

The author takes this opportunity of expressing his gratitude to the past and present members of the Cavendish Cyclotron Laboratory for assistance in running the cyclotron. He wishes to thank the Royal Commission for the Exhibition of 1851 for the award of a Science Scholarship.

A point H is known to lie on a given bounded interval ℋ. A searcher wishes to locate H by making successive guesses g1, g2, …, each with the knowledge of whether the previous guesses were too high or low, or exactly right. Under these circumstances it is easy to devise a search strategy which ensures the convergence of the gi to H. One such strategy is the ‘halving’ strategy which always guesses the midpoint of the interval on which H is currently known to lie. The problem becomes well defined, and more difficult, if the searcher has to minimize a given cost function which in some way measures the speed of convergence of the gi to H.

It has been shown recently that a fruitful method of studying the formation of waves on the sea surface is through the average intensity of reflected sunlight, as seen from different angles ((3), (4)). This gives, in effect, the statistical distribution of the components of surface slope.

Following the same line of thought, we may inquire what information could be derived from the distribution of the sizes of the reflected images of the sun. The size of an image depends essentially on the total curvature of the surface at the point of reflexion (see § 2).

We consider a certain method of effectively calculating functions of the positive integers, related to the ‘transfinite recursion’ of Ackermann(1). It arises by use of well-ordered series, and one might hope that the functions so generated could be classified according to the ordinal of the series involved, but we shall see that the use of well-ordered series is not at all essential, and in any case no ordinal other than ω need be used. We investigate how any calculable function (that is, general recursive) can be derived by ordinal recursion (as we name our method), and prove a best possible result.

An Archimedean solid (in three dimensions) may be defined as a polyhedron whose faces are regular polygons of two or more kinds and whose vertices are all surrounded in the same way. For example, the “great rhombicosidodecahedron” is bounded by squares, hexagons and decagons, one of each occurring at each vertex. Thus any Archimedean solid is determined by the faces which meet at one vertex, and therefore by the shape and size of the “vertex figure,” which may be defined as follows. Suppose, for simplicity, that the length of each edge of the solid is unity. The further extremities of all the edges which meet at a particular vertex lie on a sphere of unit radius, and also on the circumscribing sphere of the solid, and therefore on a circle. These points form a polygon, called the “vertex figure,” whose sides correspond to the faces at a vertex and are of length 2 cos π/n for an n-gonal face. Thus the vertex figure of the great rhombicosi-dodecahedron is a scalene triangle of sides .

The possibility of instability arising as overstability in the magnetohydrodynamic Bénard problem is discussed. Results are derived for large Hartmann numbers when the regions outside the fluid layer are conducting or insulating, the interfaces being rigid or free.

Introduction. The subject of the mixtures of probability distributions has aroused a fresh interest in the fields of probability and statistics. Several authors, including Blischke, Rider, Robbins, Teicher, Patil and Seshadri, have discussed a variety of the associated probabilistic and statistical problems in varying details in the recent past. This paper attempts to solve by using the methods of infinite matrices some of the problems of the identifiability of countable mixtures of discrete probability distributions. It appears that here is still another area where Mathematics and Statistics can help one another grow. We are extremely thankful to Dr P. Vermes of Birkbeck College of the University of London for developing some theory of infinite matrices relevant to a couple of problems discussed in this paper. While most of the results discussed below are believed to be new, a few of them can be shown to be immediate consequences of a powerful result due to Teicher ((7)) obtained by using a different approach.