7,884 research outputs found
Molecular, morphological, and phytochemical evidence for a broad species concept of Plagiochila bifaria (Hepaticae)
Debate over the synonymy of the European Plagiochila killarniensis and the Neotropical P bifaria of R sect. Arrectae has focused on differences in secondary metabolite composition. The broad morphological species concept of R bifaria proposed in recent papers has now been tested by comparing nrDNA ITS1 and ITS2 sequences of R bifaria populations encompassing several different morpho- and chemotypes from the British Isles, Tenerife, Costa Rica, Brazil, Ecuador, and Bolivia, with sequences of other species of R sects. Arrectae, Rutilantes, and Fuscoluteae. Phylogenetic analyses demonstrate that specimens of P. bifaria form a well supported clade within Plagiochila sect. Arrectae. Sequences of R bifaria from the British Isles, Tenerife, and Ecuador, representing the "methyl everninate" chemotype, form a well supported subclade within the P bifaria clade. Sequences of specimens from Costa Rica, Brazil, and Bolivia are placed in the basal part of the R bifaria clade. The data support a broad species concept of P bifaria. The different chemotypes do not warrant distinct taxonomic ranks. Plagiochila centrifuga and P. compressula are treated as new synonyms of R bifaria
Parafermionic conformal field theory on the lattice
Finding the precise correspondence between lattice operators and the
continuum fields that describe their long-distance properties is a largely open
problem for strongly interacting critical points. Here we solve this problem
essentially completely in the case of the three-state Potts model, which
exhibits a phase transition described by a strongly interacting 'parafermion'
conformal field theory. Using symmetry arguments, insights from integrability,
and extensive simulations, we construct lattice analogues of nearly all the
relevant and marginal physical fields governing this transition. This
construction includes chiral fields such as the parafermion. Along the way we
also clarify the structure of operator product expansions between order and
disorder fields, which we confirm numerically. Our results both suggest a
systematic methodology for attacking non-free field theories on the lattice and
find broader applications in the pursuit of exotic topologically ordered phases
of matter.Comment: 27 pages, 4 figures; v2 added reference
Ultrafast Raman-induced Kerr-effect of water: Single molecule versus collective motions.
Prospects of accelerator and reactor neutrino oscillation experiments for the coming ten years
We analyze the physics potential of long baseline neutrino oscillation
experiments planned for the coming ten years, where the main focus is the
sensitivity limit to the small mixing angle . The discussed
experiments include the conventional beam experiments MINOS, ICARUS, and OPERA,
which are under construction, the planned superbeam experiments J-PARC to
Super-Kamiokande and NuMI off-axis, as well as new reactor experiments with
near and far detectors, represented by the Double-Chooz project. We perform a
complete numerical simulation including systematics, correlations, and
degeneracies on an equal footing for all experiments using the GLoBES software.
After discussing the improvement of our knowledge on the atmospheric parameters
and by these experiments, we investigate the
potential to determine within the next ten years in detail.
Furthermore, we show that under optimistic assumptions and for
close to the current bound, even the next generation of experiments might
provide some information on the Dirac CP phase and the type of the neutrino
mass hierarchy.Comment: 38 pages, 13 figures, Eqs. (1) and (5) corrected, small corrections
in Figs. 8, 9, and Tab. 4, discussion improved, ref. added, version to appear
in PRD, high resolution figures are available at
http://www.sns.ias.edu/~winter/figs0403068.htm
Collective dynamics of two-mode stochastic oscillators
We study a system of two-mode stochastic oscillators coupled through their
collective output. As a function of a relevant parameter four qualitatively
distinct regimes of collective behavior are observed. In an extended region of
the parameter space the periodicity of the collective output is enhanced by the
considered coupling. This system can be used as a new model to describe
synchronization-like phenomena in systems of units with two or more oscillation
modes. The model can also explain how periodic dynamics can be generated by
coupling largely stochastic units. Similar systems could be responsible for the
emergence of rhythmic behavior in complex biological or sociological systems.Comment: 4 pages, RevTex, 5 figure
A Universal Action Formula
A universal formula for an action associated with a noncommutative geometry,
defined by a spectal triple (\Ac ,\Hc ,D), is proposed. It is based on the
spectrum of the Dirac operator and is a geometric invariant. The new symmetry
principle is the automorphism of the algebra \Ac which combines both
diffeomorphisms and internal symmetries. Applying this to the geometry defined
by the spectrum of the standard model gives an action that unifies gravity with
the standard model at a very high energy scale.Comment: This is a short non technical letter based on the longer version,
hep-th/9606001. Tex file, 10 page
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