In 1939 Coxeter published three infinite families of group presentations. He studied their properties, in particular determining when groups defined by members of the families are infinite and the structure of finite ones. Eight presentations remained for which the finiteness question was unsettled. We show that two of these eight presentations define finite groups (for which we give comprehens...

We study SO(m) covariant Matrix realizations of ∑m i=1 X 2 i = 1 for even m as candidate fuzzy odd spheres following hep-th/0101001. As for the fuzzy four sphere, these Matrix algebras contain more degrees of freedom than the sphere itself and the full set of variables has a geometrical description in terms of a higher dimensional coset. The fuzzy S is related to a higher dimensional coset SO(2...

We construct the covariant κ-symmetric superstring action for type IIB superstring on plane wave space supported by Ramond-Ramond background. The action is defined as a 2d sigma-model on the coset superspace. We fix the fermionic and bosonic light-cone gauges in the covariant Green-Schwarz superstring action and find the light-cone string Lagrangian and the Hamiltonian. The resulting light-cone...

Three results about the groups A7 , As) L3(2), L4(2) and the Lorimer-Rahilly plane are proved in a unified way. My principal contact with Alan Rahilly was through a certain projective plane of order 16. He had found it as one of an infinite class of generalized Hall planes he constructed in his thesis at Sydney University [9], while I had found it as an isolated plane which I identified through...

Given a finite presentation of a group G, proving properties of G can be difficult. Indeed, many questions about finitely presented groups are unsolvable in general. Algorithms exist for answering some questions while for other questions algorithms exist for verifying the truth of positive answers. An important tool in this regard is the Todd-Coxeter coset enumeration procedure. It is possible ...

Let A be an expanding n n integer matrix with j det(A)j = m. A standard digit set D for A is any complete set of coset representatives for Z n =A(Z n). Associated to a given D is a set T(A; D), which is the attractor of an aane iterated function system, satisfying T = d2D (T + d). It is known that T(A; D) tiles R n by some subset of Z n. This paper proves that every standard digit set D gives a...

We study some challenging presentations which arise as groups of deeciency zero. In four cases we settle niteness: we show that two presentations are for nite groups while two are for innnite groups. Thus we answer three explicit questions in the literature and we provide the rst published deeciency zero presentation for a group with soluble length seven. The tools we use are coset enumeration ...

Direct search methods are mainly designed for use in problems with no equality constraints. However, there are many instances where the feasible set is of measure zero in the ambient space and no mesh point lies within it. There are methods for working with feasible sets that are (Riemannian) manifolds, but not all manifolds are created equal. In particular, reductive homogeneous spaces seem to...

Let G be a finite group, and X a subset of G. The Cayley graph of G with respect to X , written Cay(G,X) has two different definitions in the literature. The vertex set of this graph is the group G. In one definition, there is an arc from g to xg for all g ∈ G and x ∈ X ; in the other definition, for the same pairs (g,x), there is an arc from g to gx. Cayley graphs are generalised by coset grap...