Let ℳg be the coarse moduli scheme of curves of genus g. For an algebraically closed field k define is a quasiprojective algebraic variety over k, its dimension being 3g – 3 for g ≥ 2, 1 for g = 1, and 0 for g = 0. It can be considered as the moduli variety for the classes of birationally equivalent curves of genus g over k. For 0 < g, g′ and n ≥ 1 let be the subset of those points of whose corresponding curves possess a rational map of degree n into a curve of genus g′ over k.

Let K be a hyper-cube of side 2 in n dimensions where n is any positive integer, and H an arbitrary, fixed (n − 1)-dimensional hyper-plane through the centre of K.

In this paper, we study the structure of certain infinite-dimensional Jordan algebras admitting an inner product. These algebras, called J*-algebras in the sequel, have already been considered in (4) in connexion with the norm uniqueness problem for non-associative algebras. We deal here with the structure and classification of these algebras. Existence of self-adjoint idempotents plays a central role in the classification problem.

Let denote a Hilbert space (real or complex), with inner product (|). In order to present our notation, we recall that if is a vector subspace of (and ‘vector sub-spaces’ will always be closed), with orthocomplement , a partial isometry V with initial domain is a linear operator in which preserves length, and so inner-product, in and is zero in is the final domain of V, and it is easy to verify that V*, the adjoint operator, is also a partial isometry, with initial domain and final domain .

Let U be a unilateral shift of arbitrary (perhaps uncountable) multiplicity on a Hilbert space. Following Rosenblum (5), an operator A is said to be a Hankel operator relative to U if

Hartman (2) has characterized the compact Hankel operators relative to the unilateral shift of multiplicity one as the Hankel operators with symbol in H∞ + C(T). Using the usual function space model for representing the unilateral shift, Page ((4), theorem 10) has extended Hartman's theorem to unilateral shifts of countable multiplicity. We give a model-free proof of Hartman's theorem which applies to shifts of arbitrary multiplicity. The proof turns on the observation that a compact operator acts compactly on a certain algebra of operators.

A deep result in the theory of W*-tensor products, the Commutation theorem, states that if M and N are W*-algebras faithfully represented as von Neumann algebras on the Hilbert spaces H and K, respectively, then the commutant in L(H ⊗ K) of the W*-tensor product of M and N coincides with the W*-tensor product of M′ and N′. Although special cases of this theorem were established successively by Misonou (2) and Sakai (3), the validity of the general result remained conjectural until the advent of the Tomita-Takesaki theory of Modular Hilbert algebras (6). As formulated, the Commutation theorem is a spatial result; that is, the W*-algebras in its statement are taken to act on specific Hilbert spaces. Not surprisingly, therefore, known proofs rely heavily on techniques of representation theory.

This paper is concerned with the engulfing of a polyhedron X from one end δ_ W of a cobordism (W, δ_ W, δ+W). In the case where the pair (W, δ_ W) is highly connected this version of Engulfing is dealt with in Rourke and Sanderson (2) by combining the method used in the proof of the h-cobordism theorem (eliminating handles) with a simple procedure involving handle-moves. A handle-move is an ambient isotopy which shrinks a handle H onto a small regular neighbourhood of its fibre D. Thus, if a closed polyhedron misses D, a handle-move can be applied to cause X to slip off H.

The concept of sectional convergence (AK) in FK-spaces was investigated by Zeller in (20). In (5) and (6), Garling investigated convergent and bounded sections in more general topological sequence spaces. Many of the results hold for Toeplitz sections in sequence spaces. A topological sequence space has the property of Toeplitz sectional convergence (TK) if and only if the unit sequences form a Toeplitz basis. In section 3, we present characterizations of Toeplitz sectional boundedness (TB) and functional Toeplitz sectional convergence (FTK) in terms of βT- and γT-duality. In section 4, we apply our results to summability fields. These results are related to the Hardy-Bohr property of multipliers for Cesàro summable sequences of positive order. In section 5, we characterize the properties TK and TB in FK-spaces by factorization statements.

1. In (4) Bott and Heitsch discussed certain classifying spaces of importance in the study of foliations of various types. For example they studied the space BГq which helps to classify real foliations of codimension q and proved that a canonical map

induces an injection in integral cohomology for q ≥ 2. Similar results hold for classifying spaces BUГq and BSГq related to complex and oriented foliations respectively. The object of this paper is to demonstrate that the canonical maps referred to above also induce injections in integral K-theory.

We shall consider exclusively algebraic non-singular quasi-projective irreducible varieties over an algebraically closed field. If V is such a variety will be the Chow ring of rational equivalence classes of cycles of V

and the group homomorphism defined by any proper morphism φ: V1 → V2. Also

denotes the ring homomorphism defined by φ.

In this paper we continue the investigation of positive-moment problems, begun in (4). For an arbitrary index set A we consider a family (fα)α ∈ A of measurable real-valued functions on a measure-space (X, µ). We suppose throughout that

where (Xm) is an increasing sequence of measurable subsets of X and where, for each α in A and each m, fα is µ-integrable over Xm. Let (сα)α ∈ A be a given family of real numbers. We consider the following restricted positive-moment problem: does there exist a measurable function g on X such that 0 ≤° g ≤° 1 and such that

for every α in A? (Here the symbol ‘≤°’ indicates that the relation ≤ holds almost everywhere with respect to µ on X. Symbols ‘ = °, <°, …’ are used similarly.) If such a g exists we call (сα)α ∈ A a moment family for the problem:

Let K be a compact convex set regularly embedded in a locally convex Hausdorff topological vector space E. Let Ab(K) be the GM-space (6) with unit 1K consisting of all real valued bounded of affine functions on K and let A(K) be the GM-subspace of Ab(K) consisting of continuous functions. For properties of K and A(K), see (2). The monotone σ-envelope A(K)μ of A(K) is the smallest subset of Ab(K) containing A(K) and such that the pointwise limit of every uniformly bounded monotone sequence (an) in A(K)μ also lies in A(K)μ. In (1), Alfsen shows that when K is a metrizable simplex A(K)μ is a vector lattice. In this note it is shown conversely that if K is metrizable and A(K)μ is a vector lattice, then K is a simplex.

Two sets of conditions are found on the Q-matrix of an irreducible Markov process on a countably infinite state space which ensure that Q is regular; the first set also implies that the Markov process is ergodic, the second that it is recurrent. If the process is not irreducible, the conditions still imply regularity, and then either non-dissipativity or ‘ultimate recurrence’ (reducible analogues of ergodicity and recurrence) of the process. Conditions sufficient for ergodicity or recurrence of the process in the non-regular and regular case are also given. The results parallel (and use) results for discrete time Markov chains, and the known discrete time recurrence condition is extended to the reducible case. The conditions are illustrated by a competition process example.

The hyperbolic boundary value problem

has, for δ = 0 and each positive integer k, t-periodic solutions of period τk(ε) = 2Φ/(k2 + ε)½. For a reasonably large class of functions, f, and, for each k, certain values of ε, one at least of these solutions persists for small δ

We show that the only compact subsets of [0, 1] of measure zero are the obvious ones, and extend this idea to show that the only compact subsets of [0, 1] that generate semigroups of ℝ of measure zero are the obvious ones. We apply this last result to prove that any proper Raikov system of subsets of ℝ, with a single generator, is contained in a strictly larger proper Raikov system.

Let G be a locally compact topological group with left Haar measure, m; let M(G) denote the bounded regular Borel measures on G and let Lp(G) denote the equivalence classes of pth power integrable functions on G with respect to the left Haar measure.

The aim of this note is to construct generators for II*(MU). Generators of a similar type were constructed by various authors; Hazewinkel (2), Kozma (3) and Liulevicius (4). The construction in (4) is in fact for II*(BP) at the prime 2.

The helical solutions of the Frenkel-Thomas equations for a free spinning particle are discussed following manifestly covariant lines. For the purposes of expressing the equations in Lagrangian and Hamiltonian form, the definition of spin by H. C. Corben is not entirely satisfactory being frame-dependent. The use of a spin ‘four-vector’ is discussed which makes the solution of the equations shorter and more elegant than that of Corben. Such a derivation necessitates the use of the Frenet-Serret formulae. By basing a Lagrangian formalism on this definition of spin we show that the covariant Euler-Lagrange equations (with multipliers) lead directly to the Frenkel-Thomas equations. Such a derivation is thus an improvement on those of other authors and suggests a more suitable canonical formalism for these equations.

Suppose that f and g are measure functions and that µf and µg are the corresponding Hausdorff measures. We are interested in how relationships between f and g are reflected in relationships between µf and µg and vice versa. For example, if

Rogers ((8), p. 80) has shown that there exists a metric space Ω which has subsets A and B with µf(A) = µg(B) = 0 and, µf(B) = µg(A) = ∞. We are more interested in what happens when the metric space in question is the real line. To get the above result we need to assume that both f and g are starshaped. This is just about a best possible result since if we assume only that f is a power of t the conclusion fails. Further-more we show that there exist measure functions f and g satisfying (1) such that µf and, µg are identical. We also consider related questions: when are, µf and, µg equivalent measures and when are they identical?

The proofs depend on the construction in Theorem 3.1 of a Cantor set having pre-scribed measure properties. Although the construction is not difficult it turns out to be quite useful to appeal to the existence of such a set. We illustrate this remark by giving a short proof of a known theorem on cartesian product sets. We also make use of these ideas in section 5 where we discuss some properties of a class of net meastues and give a partial answer to a problem posed by Billingsley.

A proof is given of a general Bieberbach inequality which has the Bieberbach, Urysohn and harmonic Urysohn inequalities as special cases. This establishes a stronger as well as more general inequality than the previously mentioned inequalities. Generalizations (as well as strengthened versions) of other inequalities previously proven by the author are also obtained.