5,699 research outputs found

    Stability of five-dimensional rotating black holes projected on the brane

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    We study the stability of five-dimensional Myers-Perry black holes with a single angular momentum under linear perturbations, and we compute the quasinormal modes (QNM's) of the black hole metric projected on the brane, using Leaver's continued fraction method. In our numerical search we do not find unstable modes. The damping time of modes having l=m=2 and l=m=1 tends to infinity as the black hole spin tends to the extremal value, showing a behaviour reminiscent of the one observed for ordinary 4-dimensional Kerr black holes.Comment: 8 pages, 2 figures. Updated to match the version published on PRD. Corrected a small typo (which does not affect the results) in equation (6) of the published pape

    Aligned spin neutron star-black hole mergers: a gravitational waveform amplitude model

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    The gravitational radiation emitted during the merger of a black hole with a neutron star is rather similar to the radiation from the merger of two black holes when the neutron star is not tidally disrupted. When tidal disruption occurs, gravitational waveforms can be broadly classified in two groups, depending on the spatial extent of the disrupted material. Extending previous work by some of us, here we present a phenomenological model for the gravitational waveform amplitude in the frequency domain encompassing the three possible outcomes of the merger: no tidal disruption, "mild" and "strong" tidal disruption. The model is calibrated to 134 general-relativistic numerical simulations of binaries where the black hole spin is either aligned or antialigned with the orbital angular momentum. All simulations were produced using the SACRA code and piecewise polytropic neutron star equations of state. The present model can be used to determine when black-hole binary waveforms are sufficient for gravitational-wave detection, to extract information on the equation of state from future gravitational-wave observations, to obtain more accurate estimates of black hole-neutron star merger event rates, and to determine the conditions under which these systems are plausible candidates as central engines of gamma-ray bursts, macronovae and kilonovae.Comment: 15 pages, 7 figures, 1 tabl

    Quality of Life and Subjective Outcomes Following Maxillomandibular Advancement Surgery for the Treatment of Obstructive Sleep Apnea

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    Objective: The aim of this study was to assess outcomes related to general quality of life, daytime sleepiness and functional sleep outcomes, functional outcomes of orthognathic surgery, and facial aesthetics in patients undergoing maxillomandibular advancement (MMA) surgery for the treatment of obstructive sleep apnea (OSA). Materials and Methods: This was a cross-sectional self-report study. A questionnaire was constructed using questions drawn from previously validated questionnaires. The survey was distributed to 25 patients who underwent MMA surgery for the treatment of OSA at LHSC in London, Ontario by a single surgeon between 2002 and 2013. Results: The survey results showed that MMA patients responded positively with respect to quality of life, snoring, functional sleep outcomes and daytime sleepiness, and facial aesthetics. Nineteen (86.4%) indicated that their sleep apnea symptoms have improved since the surgery. Eighteen (81.8%) reported neutral or positive changes with respect to facial attractiveness. Nineteen (86.4%) indicated that their overall quality of life has become better since having MMA. Most patients indicated that the surgery was worthwhile and would recommend it to others suffering from OSA. Conclusions: MMA surgery for the treatment of OSA appears to have an overall positive effect on quality of life, sleep outcomes, and aesthetic outcomes. The majority of patients found the surgery worthwhile. Orthodontic treatment in conjunction with MMA appears to enhance the subjective aesthetic outcomes of treatment

    A first unbiased global determination of polarized PDFs and their uncertainties

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    We present a first global determination of spin-dependent parton distribution functions (PDFs) and their uncertainties using the NNPDF methodology: NNPDFpol1.1. Longitudinally polarized deep-inelastic scattering data, already used for the previous NNPDFpol1.0 PDF set, are supplemented with the most recent polarized hadron collider data for inclusive jet and WW boson production from the STAR and PHENIX experiments at RHIC, and with open-charm production data from the COMPASS experiment, thereby allowing for a separate determination of the polarized quark and anti-quark PDFs, and an improved determination of the medium- and large-xx polarized gluon PDF. We study the phenomenological implications of the NNPDFpol1.1 set, and we provide predictions for the longitudinal double-spin asymmetry for semi-inclusive pion production at RHIC.Comment: 36 pages, 16 figures. Final version to be published in Nucl. Phys. B. Small textual improvements and minor typos correcte

    Fermat, Leibniz, Euler, and the gang: The true history of the concepts of limit and shadow

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    Fermat, Leibniz, Euler, and Cauchy all used one or another form of approximate equality, or the idea of discarding "negligible" terms, so as to obtain a correct analytic answer. Their inferential moves find suitable proxies in the context of modern theories of infinitesimals, and specifically the concept of shadow. We give an application to decreasing rearrangements of real functions.Comment: 35 pages, 2 figures, to appear in Notices of the American Mathematical Society 61 (2014), no.

    Co-digestion of macroalgae for biogas production: an LCA-based environmental evaluation

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    Algae represent a favourable and potentially sustainable source of biomass for bioenergy-based industrial pathways in the future. The study, performed on a real pilot plant implemented in Augusta (Italy) within the frame of the BioWALK4Biofuels project, aims to figure out whether seaweed (macroalgae) cultivated in near-shore open ponds could be considered a beneficial aspect as a source of biomass for biogas production within the co-digestion with local agricultural biological waste. The LCA results confirm that the analysed A and B scenarios (namely the algae-based co-digestion scenario and agricultural mix feedstock scenario) present an environmental performance more favourable than that achieved with conventional non-renewable-based technologies (specifically natural gas - Scenario C). Results show that the use of seaweed (Scenario A) represent a feasible solution in order to replace classical biomass used for biofuel production from a land-based feedstock. The improvement of the environmental performances is quantifiable on 10% respect to Scenario B, and 38 times higher than Scenario

    Weak Equivalence Principle Test on a Sounding Rocket

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    SR-POEM, our principle of equivalence measurement on a sounding rocket, will compare the free fall rate of two substances yielding an uncertainty of E-16 in the estimate of \eta. During the past two years, the design concept has matured and we have been working on the required technology, including a laser gauge that is self aligning and able to reach 0.1 pm per root hertz for periods up to 40 s. We describe the status and plans for this project.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 201
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