Atmospheric turbulence and superstatistics

Nonequilibrium systems with large-scale fluctuations of a suitable system parameter are often effectively described by a superposition of two statistics, a superstatistics. Here we illustrate this concept by analysing experimental data of fluctuations in atmospheric wind velocity differences at Florence airport.Comment: 9 pages, 4 figures. New version to appear in Europhysics News (2005

Possible Suppression of Resonant Signals for Split-UED by Mixing at the LHC?

The mixing of the imaginary parts of the transition amplitudes of nearby resonances via the breakdown of the Breit-Wigner approximation has been shown to lead to potentially large modifications in the signal rates for new physics at colliders. In the case of suppression, this effect may be significant enough to lead to some new physics signatures being initially missed in searches at, e.g., the LHC. Here we explore the influence of this `width mixing' on the production of the nearly degenerate, level-2 Kaluza-Klein (KK) neutral gauge bosons present in Split-UED. We demonstrate that in this particular case large cross section modifications in the resonance region are necessarily absent and explain why this is so based on the group theoretical structure of the SM.Comment: 10 pages, 2 figures; discussion and references adde

Searching For Anomalous τνW\tau \nu W Couplings

The capability of current and future measurements at low and high energy $e^+e^-$ colliders to probe for the existence of anomalous, CP conserving, $\tau \nu W$ dipole moment-type couplings is examined. At present, constraints on the universality of the tau charged and neutral current interactions as well as the shape of the $\tau \to \ell$ energy spectrum provide the strongest bounds on such anomalous couplings. The presence of these dipole moments are shown to influence, e.g., the extraction of $\alpha_s(m_\tau^2)$ from $\tau$ decays and can lead to apparent violations of CVC expectations.Comment: 24 pages, 9 figure

No light shining through a wall : new results from a photoregeneration experiment

Recently, axion-like particle search has received renewed interest. In particular, several groups have started ``light shining through a wall'' experiments based on magnetic field and laser both continuous, which is very demanding in terms of detector background. We present here the 2$\sigma$ limits obtained so far with our novel set-up consisting of a pulsed magnetic field and a pulsed laser. In particular, we have found that the axion-like particle two photons inverse coupling constant $M$ is $> 8\times 10^5$ GeV provided that the particle mass $m_\mathrm{a} \sim$ 1 meV. Our results definitively invalidate the axion interpretation of the original PVLAS optical measurements with a confidence level greater than 99.9%.Comment: Version that will appear in Physical Review Letters, Vol. 99, n. 18, (2 Nov 2007

Black hole evaporation with separated fermions

In models with a low quantum gravity scale, a well-motivated reason to expect quark and lepton fields are localized but physically separated is to avoid proton decay. This could happen in a ``fat-brane'' or in an additional, orthogonal 1/TeV sized dimension in which the gauge and Higgs fields live throughout. Black holes with masses of order the quantum gravity scale are therefore expected to evaporate non-universally, preferentially radiating directly into quarks or leptons but not both. Should black holes be copiously produced at a future hadron collider, we find the ratio of final state jets to charged leptons to photons is 113:8:1, which differs from previous analyses that assumed all standard model fields live at the same point in the extra dimensional space.Comment: 5 pages, REVTe

Dynamic buckling of composite mast panels of sail ships

Composite materials are becoming more and more popular, even for large ship and offshore structures. They offer lightweight and adaptable strength and stiffness properties. In case of slender structures, where buckling is the governing limit state, such features are valuable and allow designing high performance assemblies like racing crafts as well as very large sail ships. The case of composite masts of sail ships is rather interesting as, on the one hand, relatively large, stiff but light structures are needed and, on the other hand, their reliability is crucial for ship safety. Hence, complete understanding of structural behaviour is essential to avoid too large safety factors. Indeed, such case is also the paradigm of the dynamic buckling behaviour of slender columns structures, pointing out differences between the widely used quasi-static design approach and the more realistic time domain simulations. An earlier work studied the dynamic buckling behaviour of a metallic mast. Now, the study has been extended to the much more complex case of composite masts, showing some variations due to anisotropic material properties and specific weight values different by an order of magnitude. Comprehensive description of the dynamic buckling of a typical composite mast panel is outlined in this paper and compared to results from a previous investigation on aluminium alloy mast

Large Deviations of the Free-Energy in Diluted Mean-Field Spin-Glass

Sample-to-sample free energy fluctuations in spin-glasses display a markedly different behaviour in finite-dimensional and fully-connected models, namely Gaussian vs. non-Gaussian. Spin-glass models defined on various types of random graphs are in an intermediate situation between these two classes of models and we investigate whether the nature of their free-energy fluctuations is Gaussian or not. It has been argued that Gaussian behaviour is present whenever the interactions are locally non-homogeneous, i.e. in most cases with the notable exception of models with fixed connectivity and random couplings $J_{ij}=\pm \tilde{J}$. We confirm these expectation by means of various analytical results. In particular we unveil the connection between the spatial fluctuations of the populations of populations of fields defined at different sites of the lattice and the Gaussian nature of the free-energy fluctuations. On the contrary on locally homogeneous lattices the populations do not fluctuate over the sites and as a consequence the small-deviations of the free energy are non-Gaussian and scales as in the Sherrington-Kirkpatrick model

Probabilistic Bag-Of-Hyperlinks Model for Entity Linking

Many fundamental problems in natural language processing rely on determining what entities appear in a given text. Commonly referenced as entity linking, this step is a fundamental component of many NLP tasks such as text understanding, automatic summarization, semantic search or machine translation. Name ambiguity, word polysemy, context dependencies and a heavy-tailed distribution of entities contribute to the complexity of this problem. We here propose a probabilistic approach that makes use of an effective graphical model to perform collective entity disambiguation. Input mentions (i.e.,~linkable token spans) are disambiguated jointly across an entire document by combining a document-level prior of entity co-occurrences with local information captured from mentions and their surrounding context. The model is based on simple sufficient statistics extracted from data, thus relying on few parameters to be learned. Our method does not require extensive feature engineering, nor an expensive training procedure. We use loopy belief propagation to perform approximate inference. The low complexity of our model makes this step sufficiently fast for real-time usage. We demonstrate the accuracy of our approach on a wide range of benchmark datasets, showing that it matches, and in many cases outperforms, existing state-of-the-art methods

Retromode imaging modality of epiretinal membranes

(1) Purpose: To determine the characteristics of macular epiretinal membranes (ERM) using non-invasive retromode imaging (RMI) and to compare retromode images with those acquired via fundus autofluorescence (FAF) and fundus photography. (2) Methods: Prospective observational case-series study including patients with macular ERM with no other ocular disease affecting their morphology and/or imaging quality. We compared RMI, FAF and fundus photography features by cropping and overlapping images to obtain topographic correspondence. (3) Results: In total, 21 eyes (21 patients) affected by ERM were included in this study. The mean area of retinal folds detected by RMI was significantly higher than that detected by FAF (11.85 ± 3.92 mm2 and 5.67 ± 2.15 mm2, respectively, p < 0.05) and similar to that revealed by fundus photography (11.85 ± 3.92 mm2 and 10.58 ± 3.45 mm2, respectively, p = 0.277). (4) Conclusions: RMI appears to be a useful tool in the evaluation of ERMs. It allows for an accurate visualization of the real extension of the retinal folds and provides a precise structural assessment of the macula before surgery. Clinicians should be aware of RMI's advantages and should be able to use them to warrant a wide range of information and, thus, a more personalized therapeutic approach