The intent of this paper is to show that the additive l-group of an f-ring S determines the ring structure. This is why there are so many papers that simply extend known results for abelian l-groups to f-rings. Theorem 3.1 asserts that there is a one-to-one correspondence between the f-multiplications on S and a set of homomorphisms from the positive cone of the l-group S into the positive cone of the ring (S) of polar preserving endomorphisms of the l-group S. In fact, each f-multiplication of S is determined by a homomorphism of S+ into (S)+.

Nous appellerons groupoïde un ensemble non vide, G, muni d'une loi (×) faisant correspondre à tout couple ordonné x, y ∊ G, au plus un élément z de G, appelé produit de x par y, et satisfaisant à la loi d'homogénéité (2).

We give conditions which determine if cat of a map go up when extending over a cofibre. We apply this to reprove a result of Roitberg giving an example of a $\text{CW}$ complex $Z$ such that $\text{cat}(Z)\,=\,2$ but every skeleton of $Z$ is of category 1. We also find conditions when $\text{cat}(f\,\times \,g)\,<\,\text{cat}(f)\,+\,\text{cat}(g)$. We apply our result to show that under suitable conditions for rational maps $f,\,\text{mcat}(f)\,<\,\text{cat}(f)$ is equivalent to $\text{cat(}f)\,=\,\text{cat(}f\,\times \,\text{i}{{\text{d}}_{{{S}^{n}}}})$. Many examples with $\text{mcat}(f)\,<\,\text{cat}(f)$ satisfying our conditions are constructed. We also answer a question of Iwase by constructing $p$-local spaces $X$ such that $\text{cat(}X\ \times \,{{S}^{1}}\text{)}\,\text{=}\,\text{cat(}X\text{)}\,\text{=2}$. In fact for our spaces and every $Y\,\not{\simeq }\,*,\,\text{cat}(X\,\times \,Y)\,\le \,\text{cat}(Y)\,+\,1\,\text{cat}(Y)\,+\,\text{cat}(X)$. We show that this same $X$ has the property $\text{cat}(X)=\,\text{cat}(X\,\times \,X)\,=\,\text{cl}(X\,\times \,X)\,=\,2$.

In this paper we continue the study of equationally defined classes of orthomodular lattices started in [1].

The only atom in the lattice of varieties of orthomodular lattices is the variety of all Boolean algebras. Every nontrivial variety contains it. It follows from B. Jónsson [4, Corollary 3.2] that the variety [MO2] generated by the orthomodular lattice MO2 of Figure 1 covers the variety of all Boolean algebras. I t was first shown by R. J. Greechie (oral communication) and is not difficult to see that every variety not consisting of Boolean algebras only contains [MO2]. Again it follows from the result of Jónsson's mentioned above that the varieties generated by one of the orthomodular lattices of Figures 2 to 5 cover [MO2]. The Figures 4 and 5 are to be understood in such a way that the orthocomplement of every element is on the vertical line through this element.

A set a1 …, ak of different residues mod v is called a difference set (v, k, λ) (v>k > λ) if the congruence ai — aj ≡ d (mod v) has exactly λ solutions for d ≢ 0 (mod v). Singer [4] has demonstrated the existence of a difference set (v, k, 1) if k — 1 is a prime power, and difference sets for λ > 1 have been constructed by various authors; but necessary and sufficient conditions for the existence of a (v, k, λ) are not known. It has not been possible so far to find a difference set with λ = 1 if k — 1 is not a prime power and it has therefore been conjectured that no such difference set exists.

Let p be a prime and P be a p-subgroup of a finite group G. Suppose that g ∈ G and that P ∩ Pg has index p in P. In [4], we assumed that g normalizes no non-identity normal subgroup of P. We obtained some bounds on the order of P and some applications to the case in which p = 2 and P is a Sylow 2-subgroup of 〈P, Pg〉. In this paper, we examine this situation further by considering the isomorphism ϕ of P ∩ Pg-l onto P ∩ Pg given by ϕ(x) = xg. We actually consider arbitrary isomorphisms ϕ between two subgroups of index p in P. However, an easy argument (Lemma 2.3) shows that every such ϕ can be obtained as above for some G and some g. We obtain some results concerning the nilpotence class rather than the order of P.

Local growth and decay estimates near the stationary point at the origin are derived in § 3 for solutions of the vector system,

(1)

where A(x) and B(y) are homogeneous of degree m > 1 in the components of x and y, respectively, and f* and g* are of order greater than m in ‖(x, y)‖ near the origin. It is assumed that x = 0 is asymptotically stable and y = 0 is asymptotically unstable for the homogeneous systems of first approximation,

(2)

In order to derive the estimates in § 3, various results are needed concerning solutions of a homogeneous system such as (2) (a). These are derived in § 2 and are based on work of Hahn [4; 5], Lefschetz [8], and Zubov [12].

Cartan subalgebras play a very important role in the classification of the finite-dimensional simple Lie algebras over an algebraically closed field of characteristic zero. It is well-known [5, 273] that any two Cartan subalgebras of such an algebra are conjugate, i.e. images of one another under some automorphism of the algebra. On the other hand, there exist finitedimensional simple Lie algebras over fields of finite characteristic p possessing non-conjugate Cartan subalgebras [2; 3; 4]. The simple Lie algebras discovered by Zassenhaus [6] also possess non-conjugate Cartan subalgebras, and we shall give a complete classification of Cartan subalgebras of these algebras in this paper.

We give a uniform description, in terms of Coxeter diagrams, of the Voronoi domains of the root and weight lattices of any semisimple Lie algebra. This description provides a classification not only of all the facets of these Voronoi domains but simultaneously a classification of their dual or Delaunay cells and their facets. It is based on a much more general theory that we develop here providing the same sort of information in the setting of chamber geometries defined by arbitrary reflection groups. These generalized kaleidoscopes include the classical spherical, Euclidean, and hyperbolic kaleidoscopes as special cases. We prove that under certain conditions the Delaunay cells are Voronoi cells for the vertices of the Voronoi complex. This leads to the description in terms of Wythoff polytopes of the Voronoi cells of the weight lattices.

We develop an explicit skein-theoretical algorithm to compute the Alexander polynomial of a 3-manifold from a surgery presentation employing the methods used in the construction of quantum invariants of 3-manifolds. As a prerequisite we establish and prove a rather unexpected equivalence between the topological quantum field theory constructed by Frohman and Nicas using the homology of $U\left( 1 \right)$-representation varieties on the one side and the combinatorially constructed Hennings TQFT based on the quasitriangular Hopf algebra $\mathcal{N=}\mathbb{Z}\text{/2}\ltimes {{\wedge }^{*}}{{\mathbb{R}}^{2}}$ on the other side. We find that both TQFT's are $\text{SL}\left( 2,\,\mathbb{R} \right)$-equivariant functors and, as such, are isomorphic. The $\text{SL}\left( 2,\,\mathbb{R} \right)$-action in the Hennings construction comes from the natural action on $\mathcal{N}$ and in the case of the Frohman–Nicas theory from the Hard–Lefschetz decomposition of the $U\left( 1 \right)$-moduli spaces given that they are naturally Kähler. The irreducible components of this TQFT, corresponding to simple representations of $\text{SL}\left( 2,\,\mathbb{Z} \right)\,\text{and}\,\text{Sp}\left( 2g,\,\mathbb{Z} \right)$, thus yield a large family of homological TQFT's by taking sums and products. We give several examples of TQFT's and invariants that appear to fit into this family, such as Milnor and Reidemeister Torsion, Seiberg–Witten theories, Casson type theories for homology circles à la Donaldson, higher rank gauge theories following Frohman and Nicas, and the $\mathbb{Z}/p\mathbb{Z}$ reductions of Reshetikhin–Turaev theories over the cyclotomic integers $\mathbb{Z}[{{\zeta }_{p}}]$. We also conjecture that the Hennings TQFT for quantum-$\mathfrak{s}{{\mathfrak{l}}_{2}}$ is the product of the Reshetikhin–Turaev TQFT and such a homological TQFT.

1. Introduction. A ring is defined to be standard (1) in case the following two identities hold :

(1) (wx, y, z) + (xz, y, w) + (wz, y, x) = 0,

(2) (x, y, z) + (z, x, y) − (x, z, y) = 0,

where the associator (x, y, z) is defined by (x, y, z) = (xy)z − x(yz). Albert has determined the structure of finite-dimensional, standard algebras (1).

The simple ones turn out to be either Jordan algebras or associative ones.

The Hewitt realcompactification vX of a completely regular Hausdorff space X has been widely investigated since its introduction by Hewitt [17]. An important open question in the theory concerns when the equality v(X × Y) = vX × vY is valid. Glicksberg [10] settled the analogous question in the parallel theory of Stone-Čech compactifications: for infinite spaces X and Y, β(X × Y) = βX × β Y if and only if the product X × Y is pseudocompact. Work of others, notably Comfort [3; 4] and Hager [13], makes it seem likely that Glicksberg's theorem has no equally specific analogue for v(X × Y) = vX × vY. In the absence of such a general result, particular instances may tend to be attacked by ad hoc techniques resulting in much duplication of effort.

Let π be a finite projective plane of order n containing a finite projective subplane π* of order u < n. Bruck has shown (1, p. 398) that if π contains a point that does not lie on any line of π*, then n ≥ u2 + u, while if every point of π lies on a line of π* then n = u2.

Let π be a finite projective plane of order n containing a finite affine subplane π0 of order m < n.

There has been some interest lately in equational classes of commutative semigroups (see, for example, [2; 4; 7; 8]). The atoms of the lattice of equational classes of commutative semigroups have been known for some time [5]. Perkins [6] has shown that each equational class of commutative semigroups is finitely based. Recently, Schwabauer [7; 8] proved that the lattice is not modular, and described a distributive sublattice of the lattice.

The present paper describes a “skeleton” sublattice of the lattice, which is isomorphic to A × N+ with a unit adjoined, where A is the lattice of pairs (r, s) of non-negative integers with r ≦ s and s ≧ 1, ordered component-wise, and N+ is the natural numbers with division.

Introduction. Let I be the closed real number interval: Any subset Δ of I containing at least one number interior to I, will be called a quasiconvexity generating set. To each quasiconvexity generating set Δ we associate as follows a generalized notion of convexity, here called quasiconvexity or Δ convexity. Two numbers α and β, one of which belongs to Δ, the other being determined by the relation a α + β = 1, are called complementary ratios of Δ. A set Q in a real vector space is said to be A convex if for every pair of complementary ratios α and β in Δ and every pair of points a and b lying in Q the point αa +β b also lies in Q.

Compact C*-convex subsets of Mn correspond exactly to n-th matrix ranges of operators. The main result of this paper is to discover the “right” analog of linear extreme points, called structural elements, and then to prove a generalised Krein-Milman theorem for C*-convex subsets of Mn. The relationship between structural elements and an earlier attempted generalisation, called C*-extreme points, is examined, solving affirmatively a conjecture of Loebl and Paulsen [8]. An improved bound for a C* -convex version of the Caratheodory theorem for convex sets is also given.

1. Let m be a positive square-free integer. Euclid's Algorithm is said to hold in the field if, given any non-integral element a in the field, an integer a can be found so that

We consider undirected graphs in which two vertices may be joined by more than one edge and in which a vertex may be joined to itself by one or more edges. G will always denote a graph. The set of vertices [edges] of G will be denoted by V(G) [E(G)]. G is finite or infinite according as V(G) ∪ E(G) is finite or infinite. The degree, d(ξ) or dG(ξ), of a vertex ξ of G is 2a + b, where a is the number of edges joining ξ to itself and b is the number of those joining ξ to other vertices.

The question posed by Sylvester (6) concerning the collinearity of a finite set of points in E2 having the property that each two together with some third be collinear has been the inspiration for numerous investigations. The original question was answered by the following theorem.

We show that any PG(2n, q2) is a disjoint union of (q2n+1 − 1)/ (q − 1) caps, each cap consisting of (q2n+1 + 1)/(q + 1) points. Furthermore, these caps constitute the “large points” of a PG(2n, q), with the incidence relation defined in a natural way.

A square matrix H = (hij) over the finite field GF(q2), q a prime power, is said to be Hermitian if hijq = hij for all i, j [1, p. 1161]. In particular, hii ∈ GF(q). If if is Hermitian, so is p(H), where p(x) is any polynomial with coefficients in GF(q).

Given a Desarguesian Projective Geometry PG(2n, q2), n > 0, we denote its points by column vectors:

All Hermitian matrices in this paper will be 2n + 1 by 2n + 1, n > 0.