Let G be a group given in terms of generators and denning relations. The order problem is said to be solvable for (the given presentation of) the group G if, given any element W of G (as a word in the given generators of G), we can determine the order of W in G. The power problem is solvable for G if, given any pair X, Y of elements of G, we can determine whether or not X belongs to the cyclic subgroup {Y} of G generated by Y. It is easy to see that if either of these problems is solvable for G, then the word problem is also solvable for G.

Given a normed linear space X, let S(X), X′, B(X) denote respectively the unit sphere {x: ∥x∥ = 1} of X, the dual space of X, and the algebra of all bounded linear mappings of X into X. For each x ∊ S(X) and T ∊ B(X), let Dx(x) = {f e X′:∥f∥ = f(x)= 1}, and V(T; x) = {f(Tx):f∊Dx(x)}. The numerical range V(T) is then defined by

All sets considered will be finite, and |x| will denote the cardinal number of the set X.

Let = (Ai:i∈I) be a family of subsets of a set E. A subset E′ ⊆ E is called a transversal of if there exists a bijection σ:E′→ I such that e ∈ Aσ(e) (e ∈ E′). According to a well-known theorem of P. Hall [2], the familyhas a transversal if and only iffor every subset I′ of I. Ford and Fulkerson [1] obtained (as a special case of a more general theorem) an analogous criterion for the existence of a common transversal (CT) of two families. We may state their result in the following terms.

In this note we shall employ the notation of [1] without further mention. Thus X denotes a normed space and P the subset of X × X′ given by

Given a subalgebra of B(X), the set {Φ(X,f):(x,f) ∈ P} of evaluation functional on is denoted by II. We shall prove that if X is a Banach space and if contains all the bounded operators of finite rank, then Π is norm closed in ′. We give an example to show that Π need not be weak* closed in ″. We show also that FT need not be norm closed in ″ if X is not complete.

In this paper we consider mappings induced by matrix multiplication which are defined on lattices of matrices whose coordinates come from a fixed orthomodular lattice L (i.e. a lattice with an orthocomplementation denoted by ′ in which a ≦ b ⇒ a ∨ (a′ ∧ b) = b). will denote the set of all m × n matrices over L with partial order and lattice operations defined coordinatewise. For conformal matrices A and B the (i,j)th coordinate of the matrix product AB is defined to be (AB)ij = Vk(Aik ∧ BkJ). We assume familiarity with the notation and results of [1]. is an orthomodular lattice and the (lattice) centre of is defined as , where we say that A commutes with B and write . In § 1 it is shown that mappings from into characterized by right multiplication X → XP (P ∈ ) are residuated if and only if p ∈ ℘ (). (Similarly for left multiplication.) This result is used to show the existence of residuated pairs. Hence, in § 2 we are able to extend a result of Blyth [3] which relates invertible and cancellable matrices (see Theorem 3 and its corollaries). Finally, for right (left) multiplication mappings, characterizations are given in § 3 for closure operators, quantifiers, range closed mappings, and Sasaki projections.

9-Carbamoylfluorene with lithium aluminium hydride, 9-cyanofluorene with this reagent and aluminium trichloride, or (on one occasion) treatment of the oximes of 9-formylfluorene with thionyl chloride yield 9,9′-dicyano-9,9′-bifluorenyl. 9-Bromofluorene and ethanolic potassium cyanide yield 9-cyano-9,9′-bifluorenyl, and 9-formylfluorene when kept in ether for a month gives 9,9′-diformyl-9,9′-bifluorenyl. The so-called α-oxime of 9-formylfluorene described in the literature contains about 33 per cent of the higher melting β-oxime. Reduction of the oximes with zinc and acetic acid yields di(9-fluorenylidenemethyl)amine, previously obtained by other methods. A new method for the preparation of 9-aminomethylenefluorene is described and its structure has been confirmed. Many 9-substituted and 9,9′-disubstituted fluorenes exhibit characteristic absorption at 1920–1880 and 1960–1940 cm.−1.

G. Lallement [4] has shown that the lattice of congruences, Λ(S), on a completely 0-simple semigroup S is semimodular, thus improving G. B. Preston's result [5] that such a lattice satisfies the Jordan-Dedekind chain condition. More recently, J. M. Howie [2] has given a new and more simple proof of Lallement's result using work due to Tamura [9]. The purpose of this note is to extend the semimodularity result to primitive regular semigroups, to establish a theorem relating certain congruence and quotient lattices, and to provide a theorem for congruences on any regular semigroup.

Let A = (aij) be an n × n complex matrix. The permanent of this matrix is

where the sum is taken over all permutations p of the set {1, …, n}.

In a recent paper [1] E. H. Lieb proved an interesting theorem (see below) which he applied to verify some conjectures of M. Marcus and M. Newman. The purpose of this note is to give a simple proof of Lieb's theorem.

A vector lattice W is boundedly complete when each subset {aj:j ∊ J} of W which is bounded above by an element of W has a least upper bound in W. The least upper bound of {aj:j ∊ J} is denoted by and the greatest lower bound by whenever these exist.

Let (X, ≺) denote a non-empty (partially) ordered set, or more generally a non-empty set X with an arbitrary transitive relation ≺ on it. The relation ≺ will be fixed throughout what follows, so to simplify the notation we often write (X, ≺) as X. A successor of x ∈ X is an element y ∈ X such that x ≺ y; thus x may or may not be a successor of itself. As usual, a subset A ⊂ X is cofinal if each x ∈ X has a successor in A. A partition of X is a family of (pairwise) disjoint nonempty subsets of X whose union is X.

The object of this paper is first to generalize the basic inequality of the large sieve method to exponential sums in many variables, and then to deduce results for algebraic number fields that are analogous to known results for the rational field.

In recent years, functions of n variables whose partial derivatives are measures, have been found to retain the properties of functions of bounded variation of one variable to a remarkable degree [e.g., G1, G2, G3, K, Z, and especially the announcement F].

It has been shown by Mirsky and Perfect [1] that the theorem of Rado [2], linking matroid theory and transversal theory, has important applications in combinatorial theory. In this note I use it to obtain necessary and sufficient conditions for two families of sets to have a common transversal containing a given set, and then I show how it may be used to obtain a variant of a well-known theorem that was obtained by Hoffman and Kuhn [3] using linear programming methods.

It was conjectured by Artin [1] that each non-zero integer a unequal to +1, −1 or a perfect square is a primitive root for infinitely many primes p. More precisely, denoting by Na(x) the number of primes p ≤ x for which a is a primitive root, he conjectured that

where c(a) is a positive constant. This conjecture has recently been proved by C. Hooley [2] under the assumption that the Riemann hypothesis holds for fields of the type .

Let G be any group and G′ its derived, then G/G′—the group G made abelian—will be denoted by Ga. Over any ring R, denote by E2(R) the group generated by the matrices as x ranges over R; the structure of E2(R)a has been described in a recent theorem [2; Th. 9.3] for certain rings R, the “quasi-free rings for GE2” (cf. §2 below). Now over a commutative Euclidean domain, E2(R) is just the special linear group SL2(R); this suggests applying the theorem to the ring of integers in a Euclidean number field. However, the only number fields whose rings were shown to be quasi-free for GE2 in [2] were the non-Euclidean imaginary quadratic fields. In fact that leaves the application of Th. 9.3 of [2] to the ring of Gaussian integers unjustified (I am indebted to J.-P. Serre for drawing this oversight to my attention). In order to justify this application one would have to show either (a) that the Gaussian integers are quasi-free for GE2., or (b) that Th. 9.3 of [2] holds under weaker hypotheses which are satisfied by the Gaussian integers. Our object in this note is to establish (b)–indeed our only course, since the Gaussian integers turn out to be not quasi-free.

In a paper [1] published in 1956, David Gale introduced the idea of representing a convex polytope by a diagram (now called a Gale diagram). Later work by Gale, T. S. Motzkin, and more recently by M. A. Perles and B. Grünbaum,has shown the importance of this idea. Using it, a large number of results which were formerly inaccessible have been proved. For an account of Gale diagrams and their applications, the reader is referred to Grünbaum's recent book [2; §5.4 and §6.3] and we shall largely follow the notations used there.

Let Cn be the n-dimensional complex number space of the complex variables z1,…, zn and be the unit hypersphere. Further, let G be the group of all holomorphic automorphisms of K, then G is a n(n + 2)-dimensional real Lie group. In [3] the author has proved that for any P∈∂K (the boundary of K) there exists a decomposition of G in the form , where G0 is the group of all analytic rotations about the origin and is a 2n-dimensional real Lie group, whose underlying topological space is K, which acts transitively on K and P is a fixed point of all elements of .