44,936 research outputs found
Baryon Magnetic Moments in the 1/N_c Expansion with Flavor Symmetry Breaking
The magnetic moments and transition magnetic moments of the ground state
baryons are analyzed in an expansion in 1/N_c, SU(3) flavor symmetry breaking
and isospin symmetry breaking. There is clear evidence in the experimental data
for the hierarchy of magnetic moments of the combined expansion in 1/N_c and
flavor breaking. SU(3) breaking in the magnetic moments is expected to be
enhanced relative to that of other hadronic observables, and significant SU(3)
breaking is found.Comment: 21 pages, 1 figure, CLAS reference update
Exact simulation of the Wright-Fisher diffusion
The Wright-Fisher family of diffusion processes is a widely used class of
evolutionary models. However, simulation is difficult because there is no known
closed-form formula for its transition function. In this article we demonstrate
that it is in fact possible to simulate exactly from a broad class of
Wright-Fisher diffusion processes and their bridges. For those diffusions
corresponding to reversible, neutral evolution, our key idea is to exploit an
eigenfunction expansion of the transition function; this approach even applies
to its infinite-dimensional analogue, the Fleming-Viot process. We then develop
an exact rejection algorithm for processes with more general drift functions,
including those modelling natural selection, using ideas from retrospective
simulation. Our approach also yields methods for exact simulation of the moment
dual of the Wright-Fisher diffusion, the ancestral process of an infinite-leaf
Kingman coalescent tree. We believe our new perspective on diffusion simulation
holds promise for other models admitting a transition eigenfunction expansion.Comment: 36 pages, 2 figure, 2 tables. This version corrects an error in the
proof of Lemma 6.
Linking teaching and research in disciplines and departments
This paper supports the effective links between teaching and discipline-based research in disciplinary communities and in academic departments. It is authored by Alan Jenkins, Mick Healey and Roger Zetter
Introduction to Library Trends 55 (3) Winter 2007: Libraries in Times of War, Revolution and Social Change
published or submitted for publicatio
The Kinetics of the Exchange of Tritium between Hypophosphorous Acid and Water
We have measured the rates of exchange of radioactive hydrogen (tritium) between tritiated water, HTO, and the thwo "undissociable" hydrogens of monobasic hydrophosphorous acid, H3PO2
An asymptotic sampling formula for the coalescent with Recombination
Ewens sampling formula (ESF) is a one-parameter family of probability
distributions with a number of intriguing combinatorial connections. This
elegant closed-form formula first arose in biology as the stationary
probability distribution of a sample configuration at one locus under the
infinite-alleles model of mutation. Since its discovery in the early 1970s, the
ESF has been used in various biological applications, and has sparked several
interesting mathematical generalizations. In the population genetics community,
extending the underlying random-mating model to include recombination has
received much attention in the past, but no general closed-form sampling
formula is currently known even for the simplest extension, that is, a model
with two loci. In this paper, we show that it is possible to obtain useful
closed-form results in the case the population-scaled recombination rate
is large but not necessarily infinite. Specifically, we consider an asymptotic
expansion of the two-locus sampling formula in inverse powers of and
obtain closed-form expressions for the first few terms in the expansion. Our
asymptotic sampling formula applies to arbitrary sample sizes and
configurations.Comment: Published in at http://dx.doi.org/10.1214/09-AAP646 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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