In [4] we have given a simple method of estimating trigonometrical sums over prime numbers. Here we show how the argument can be adapted in order to give estimates for the distribution of αp modulo 1 which are sharper than those obtained by I. M. Vinogradov [5], [6]. Vinogradov uses the sieve of Eratosthenes to relate the sum

to the bilinear form

the function μ being the Mobius function. When d1 … ds is small compared with N this can be treated in a fairly straightforward manner. However, in order to treat the terms with d1 …ds close to N, Vinogradov has to introduce an argument of a rather recondite combinatorial nature.

The object of this paper is to generalize to infinite CW complexes the known pull-back theorems or fracture lemmas concerning maps from finite CW complexes to localizations and completions.

§1. Let pi denote the i-th prime number, and let

The prime number theorem implies Er ≤ r. Bombieri and Davenport [1] showed that

improving earlier results of Erdős, Rankin and Ricci. Their basic result (corresponding to Lemma 1 below) counts pairs of primes differing by 2n with some weight t(n).

Let l be a rational prime, and let ℤl denote the ring of l-adic integers. Let k0 be a finite extension field of the rational numbers ℚ, and let K be a ℤl-extension of k0 (i.e., Gal (K/k0) is topologically isomorphic to the additive group of Zl). Let the intermediate fields be denoted as follows:

where knk0 is a cyclic extension of degree ln, and Let An denote the l-class group of kn (i.e., the Sylow l-subgroup of the ideal class group of kn). It is known that the order of An is given by , with

Let L/K be a quadratic extension of algebraic number fields, and D a central L-division algebra of finite L-dimension d2. If - is an involution (i.e., a ring antiautomorphism of period two) of D, we write S(-) for the set of - symmetric elements of D:

An arithmetic function f(n) is said to be additive, if it satisfies the relation f(ab) = f(a) + f(b), for every pair of coprime integers a and b; and stronglya dditive if, in addition, f(pm) = f(p) for every prime-power pm.

We let K(a1a2, ak) denote the continuant formed from the positive integers a1 …, ak; that is,

Of course, K(a1, …, an) is the denominator of the continued fraction

We use the convention that K (empty set) = 1.

An internal wave motion, below a layer of uniform fluid, induces a weak current on the free surface in the form of a long wave with phase velocity cI. A uniform progressive train of surface waves, whose wave-length is much shorter than that of the current is incident on it from infinity and undergoes modification. In particular, when the group velocity cg of the progressive wave is equal to cI, the resonance takes place and then, even though the amplitude of the current is small, the interaction builds up near a number of its wavelengths until the train of surface waves is significantly modified. The equations governing the modifications are derived, using the method of multiple scales, and the roles of the Döppler shift and the radiation stress in resonant situations are elucidated. Three-dimensional interactions are discussed and an analogy is drawn between the fundamental equation describing the interactions and Schrödinger's equation.

In this paper we continue our study of the values taken by Euler's ø-function begun in [1]–[3]. Let ør(n) be the iterated ø-function, that is ør(n) = ø{ør-1(n} where ø1 = ø1. Let

Let K be a successor cardinal. Call an regularizing family (for short, a regularizing family) if Card ℱ = k and for each with Card . In [7], Prikry proved, assuming V = L, that if is an ultrafilter on K which is uniform (Card X = K, each ) then is regular (some forms a regularizing family).†

The question, whether a given element of a C*-algebra has an image of rank one in some faithful representation, was studied in [3]. Such elements were characterised there by the property of being “single” (as defined below). As was pointed out in [3], Section 5, this criterion fails for general Banach algebras and the purpose of this paper is to provide a stronger condition giving the required representation property for any semi-simple Banach algebra.

Let μ be a Borel measure on a completely regular space X, and denote by ℱ the σ-algebra of all μ*-measurable subsets of X. Suppose that, as an abstract measure space, (X, ℱ, μ) is isomorphism mod zero with the standard Lebesgue space (I, ℒ, m) via an isomorphism φ : X → I. In this note we attempt to answer the following question: Under what conditions can the isomorphism φ be chosen to be a homeomorphism mod zero? When X is compact, the existence of such a homeomorphism was established in [3, §4] under the assumption of uniform regularity of μ. Whether or not the result can be established without this assumption, was posed as an open question there. Here, we give necessary and sufficient conditions for the existence of the above homeomorphism, together with various examples showing, among other things, that the assumption of uniform regularity used in [3, §4] cannot be dropped.

Littlewood [5, Problem 4.19, originally 4] conjectured that there is an absolute constant C > 0 such that, for every sequence of distinct integers n1, n2, n3, …, if

then

Cohen [2] showed

for some absolute constant C, with b = 1/8. Davenport [3] gave a more explicit version of Cohen's proof and improved the estimate to b = 1/4. Pichorides [6] added another refinement to obtain b = ½, and has, more recently, obtained ‖fN‖1>C(log N)1/2. This seems to be the best estimate so far without restriction on the sequences. We shall show that the methods of Davenport and Pichorides may be extended to obtain better results for certain classes of sequences. Specifically, we prove the following theorems.

It is proved that, if R is a set of r vertices of an n–dimensional cube, then the number of distinct mid-points of line-segments joining pairs of points of R (including the points of R themselves as mid-points) is at least rx, where

This result is (in a sense) best possible.

The Fourier transform f of a function is defind by

t ∊ ℝn. A(ℝn) is the isometric image of L1(ℝn) under the Fourier transformation. We extend the Fourier transformation to a mapping of ℒ(ℝn) to itself and denote by A′(ℝn) the isometric image of L∞(ℝn).

In finding the resistance to the motion of a closely fitting plug along a tube filled with fluid, allowance must be made for the leakage of fluid through the gap between the plug and the tube. If there is no leakage, theoresistance is theoretically infinite. For a plug of length d in a tube of radius a and with a gap b between the plug and tube, the dominant term in the resistance comes from the flow in the gap, and is proportional to da/b. If, however, the plug is very short, so that it may be considered as a disk, the calculation of the flow near the disk shows that the resistance is now proportional to aln (a/b) and the presence of the disk increases the force on the tube by an amount equivalent to an increase in length of the tube by only a few radii.

Let denote the class of all compact convex sets in Euclidean n-dimensional space En, and let y be the collection of those members of k which are centrally symmetric. The topology in is that induced by the Hausdorff metric.

A quasi-simplex of ℝd is the closure of a Choquet simplex of ℝd. We characterize these quasi-simplices and we use this characterization to describe the line-free Choquet simplices of ℝd.

An incident sound field is scattered by a semi-infinite rigid screen with periodically arranged slits or circular apertures and an approximate solution is sought when the slit (or aperture) width is small and the wavelength is large compared with the separation. An integral equation formulation is used to show that the scattering properties of the screens are equivalent to those of a homogeneous compliant plate. The effective compliance is estimated and is found to be essentially uniform over the plate, with corrections close to the edges.

It is well known that every set of at least d + 2 points of ℝd may be decomposed into two disjoint parts whose convex hulls intersect. This result, called Radon's theorem, has been generalized in different ways. The easiest generalization consists in replacing the field of real numbers by any ordered division ring (field or skew-field): here the original proof remains valid. A less immediate generalization is the following one, conjectured by Birch [1] and proved by Tverberg [3]:

Every set of at least r(d + 1) – d points of ℝd may be decomposed into r disjoint parts whose convex hulls intersect.