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