Randall Gray

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We prove the following results: (1) Every group is a maximal subgroup of some free idempotent generated semigroup. (2) Every finitely presented group is a maximal subgroup of some free idempotent generated semigroup arising from a finite semigroup. (3) Every group is a maximal subgroup of some free regular idempotent generated semigroup. (4) Every finite(More)
We have studied the Cabibbo-suppressed decay mode D0 → K+K−π0 using a Dalitz plot technique and find the strong phase difference δD ≡ δK∗−K+ − δK∗+K− = 332◦ ± 8◦ ± 11◦ and relative amplitude rD ≡ aK∗−K+ / aK∗+K− = 0.52 ± 0.05 ± 0.04. This measurement indicates significant destructive interference between D0 → K+(K−π0)K∗− and D0 → K−(K+π0)K∗+ in the Dalitz(More)
The foreskin is the main site of heterosexual human immunodeficiency virus (HIV) acquisition in uncircumcised men, but functional data regarding T-cell subsets present at this site are lacking. Foreskin tissue and blood were obtained from Ugandan men undergoing elective adult circumcision. Tissue was treated by mechanical and enzymatic digestion followed by(More)
Using data collected with the CLEO detector operating at the CESR e+e− collider at √ s = 3.974.26GeV, we investigate 15 charmonium decay modes of the ψ(4040), ψ(4160), and Y (4260) resonances. We confirm, at 11σ significance, the BaBar Y (4260)→ π+π−J/ψ discovery, make the first observation of Y (4260) → π0π0J/ψ (5.1σ), and find the first evidence for Y(More)
We have studied the leptonic decay D+ s → τ ντ , via the decay channel τ + → eνeν̄τ , using a sample of tagged D+ s decays collected near the D ∗± s D ∓ s peak production energy in e +e− collisions with the CLEO-c detector. We obtain B(D+ s → τ ντ ) = (5.30± 0.47± 0.22)% and determine the decay constant fDs = (252.5±11.1±5.2) MeV, where the first(More)
This paper presents a discussion of the possible influence of incomputability and the incompleteness of the mathematics as a source of apparent emergence in complex systems. The suggestion is made that the analysis of complex systems as a specific instance of a complex process may be subject to inaccessible “emergence”. We discuss models of computation(More)
Shifting the emphasis from a model to a modelling task, which involves both a computer model and a modeller, we ask what makes a problem complex. We propose that a modelling task can be seen as a set of questions-and-answers, nested at multiple levels. The role of the modeller then lies in posing the questions and choosing the best procedure to answer them,(More)
A formula for the rank of an arbitrary finite completely 0-simple semigroup, represented as a Rees matrix semigroup M[G; I,Λ;P ] , is given. The result generalises that of Ruškuc concerning the rank of connected finite completely 0-simple semigroups. The rank is expressed in terms of |I| , |Λ| , the number of connected components k of P and a number rmin(More)
The relationship between posets that are cycle-free and graphs that have more than one end is considered. We show that any locally finite bipartite graph corresponding to a cycle-free partial order has more than one end, by showing a correspondence between the ends of the graph and those of the Hasse graph of its Dedekind–MacNeille completion. If, in(More)