2,675 research outputs found
Is the Y (2175) a Strangeonium Hybrid Meson?
QCD Gaussian sum rules are used to explore the vector (JPC=1−−) strangeonium hybrid interpretation of the Y(2175). Using a two-resonance model consisting of the Y(2175) and an additional resonance, we find that the relative resonance strength of the Y(2175) in the Gaussian sum rules is less than 5% that of a heavier 2.9 GeV state. This small relative strength presents a challenge to a dominantly hybrid interpretation of the Y(2175)
Impact of observational incompleteness on the structural properties of protein interaction networks
The observed structure of protein interaction networks is corrupted by many
false positive/negative links. This observational incompleteness is abstracted
as random link removal and a specific, experimentally motivated (spoke) link
rearrangement. Their impact on the structural properties of
gene-duplication-and-mutation network models is studied. For the degree
distribution a curve collapse is found, showing no sensitive dependence on the
link removal/rearrangement strengths and disallowing a quantitative extraction
of model parameters. The spoke link rearrangement process moves other
structural observables, like degree correlations, cluster coefficient and motif
frequencies, closer to their counterparts extracted from the yeast data. This
underlines the importance to take a precise modeling of the observational
incompleteness into account when network structure models are to be
quantitatively compared to data.Comment: 17 pages, 7 figures, accepted by Physica
Harnessing multi-photon absorption to produce three-dimensional magnetic structures at the nanoscale
Three-dimensional nanostructured magnetic materials have recently been the topic of intense interest since they provide access to a host of new physical phenomena. Examples include new spin textures that exhibit topological protection, magnetochiral effects and novel ultrafast magnetic phenomena such as the spin-Cherenkov effect. Two-photon lithography is a powerful methodology that is capable of realising 3D polymer nanostructures on the scale of 100 nm. Combining this with postprocessing and deposition methodologies allows 3D magnetic nanostructures of arbitrary geometry to be produced. In this article, the physics of two-photon lithography is first detailed, before reviewing the studies to date that have exploited this fabrication route. The article then moves on to consider how non-linear optical techniques and post-processing solutions can be used to realise structures with a feature size below 100 nm, before comparing two-photon lithography with other direct write methodologies and providing a discussion on future developments
Resonant and Non-Resonant Modulated Amplitude Waves for Binary Bose-Einstein Condensates in Optical Lattices
We consider a system of two Gross-Pitaevskii (GP) equations, in the presence
of an optical-lattice (OL) potential, coupled by both nonlinear and linear
terms. This system describes a Bose-Einstein condensate (BEC) composed of two
different spin states of the same atomic species, which interact linearly
through a resonant electromagnetic field. In the absence of the OL, we find
plane-wave solutions and examine their stability. In the presence of the OL, we
derive a system of amplitude equations for spatially modulated states which are
coupled to the periodic potential through the lowest-order subharmonic
resonance. We determine this averaged system's equilibria, which represent
spatially periodic solutions, and subsequently examine the stability of the
corresponding solutions with direct simulations of the coupled GP equations. We
find that symmetric (equal-amplitude) and asymmetric (unequal-amplitude)
dual-mode resonant states are, respectively, stable and unstable. The unstable
states generate periodic oscillations between the two condensate components,
which is possible only because of the linear coupling between them. We also
find four-mode states, but they are always unstable. Finally, we briefly
consider ternary (three-component) condensates.Comment: 16 pages, 4 figures (some of which have multiple parts), to appear in
Physica D; streamlined paper; added some references and discussion concerning
experimental realizations of this work; higher-resolution copies of a couple
figures are available on the version of the document downloadable from
http://www.math.gatech.edu/~mason
Sustainability in Rangeland Systems
It is widely recognized that approaching sustainability in rangeland management needs to take many criteria into consideration which unavoidably calls for the application of multi-criteria decision making approach. Bearing conflicting objectives in mind, which are mainly conservation and utilization, we have introduced fuzzy multi-objectives decision making as a suitable approach when sustainability in rangeland management is a goal. While some extensions of the approach are discussed, interactive fuzzy multi objective linear programming, and a framework including three stages are presented to make it more applicable. The proposed approach in this paper comprises three important advantages for decision makers to apply: first, it is a useful tool to involve trade-offs analysis between the conflicting objectives; second, it challenges to uncertainty of any decision in sustainable rangeland management; and third, it considers existing alternatives under given constraints by developing new alternatives for all possible situations
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