22,601 research outputs found

    PKI Interoperability: Still an Issue? A Solution in the X. 509 Realm

    Get PDF
    There exist many obstacles that slow the global adoption of public key infrastructure (PKI) technology. The PKI interoperability problem, being poorly understood, is one of the most confusing. In this paper, we clarify the PKI interoperability issue by exploring both the juridical and technical domains. We demonstrate the origin of the PKI interoperability problem by determining its root causes, the latter being legal, organizational and technical differences between countries, which mean that relying parties have no one to rely on. We explain how difficult it is to harmonize them. Finally, we propose to handle the interoperability problem from the trust management point of view, by introducing the role of a trust broker which is in charge of helping relying parties make informed decisions about X.509 certificates

    The Oblique Orbit of the Super-Neptune HAT-P-11b

    Get PDF
    We find the orbit of the Neptune-sized exoplanet HAT-P-11b to be highly inclined relative to the equatorial plane of its host star. This conclusion is based on spectroscopic observations of two transits, which allowed the Rossiter-McLaughlin effect to be detected with an amplitude of 1.5 m/s. The sky-projected obliquity is 103_{-10}^{+26} degrees. This is the smallest exoplanet for which spin-orbit alignment has been measured. The result favors a migration scenario involving few-body interactions followed by tidal dissipation. This finding also conforms with the pattern that the systems with the weakest tidal interactions have the widest spread in obliquities. We predict that the high obliquity of HAT-P-11 will be manifest in transit light curves from the Kepler spacecraft: starspot-crossing anomalies will recur at most once per stellar rotation period, rather than once per orbital period as they would for a well-aligned system.Comment: ApJ Letters, in press [5 pages

    Hot Stars with Hot Jupiters Have High Obliquities

    Get PDF
    We show that stars with transiting planets for which the stellar obliquity is large are preferentially hot (T_eff > 6250 K). This could explain why small obliquities were observed in the earliest measurements, which focused on relatively cool stars drawn from Doppler surveys, as opposed to hotter stars that emerged later from transit surveys. The observed trend could be due to differences in planet formation and migration around stars of varying mass. Alternatively, we speculate that hot-Jupiter systems begin with a wide range of obliquities, but the photospheres of cool stars realign with the orbits due to tidal dissipation in their convective zones, while hot stars cannot realign because of their thinner convective zones. This in turn would suggest that hot Jupiters originate from few-body gravitational dynamics, and that disk migration plays at most a supporting role.Comment: ApJ Letters, in press [6 pages

    Discerning Exoplanet Migration Models Using Spin-Orbit Measurements

    Get PDF
    We investigate the current sample of exoplanet spin-orbit measurements to determine whether a dominant planet migration channel can be identified, and at what confidence. We use the predictions of Kozai migration plus tidal friction (Fabrycky and Tremaine 2007) and planet-planet scattering (Nagasawa et al. 2008) as our misalignment models, and we allow for a fraction of intrinsically aligned systems, explainable by disk migration. Bayesian model comparison demonstrates that the current sample of 32 spin-orbit measurements strongly favors a two-mode migration scenario combining planet-planet scattering and disk migration over a single-mode Kozai migration scenario. Our analysis indicates that between 34% and 76% of close-in planets (95% confidence) migrated via planet-planet scattering. Separately analyzing the subsample of 12 stars with T_eff > 6250 K---which Winn et al. (2010) predict to be the only type of stars to maintain their primordial misalignments---we find that the data favor a single-mode scattering model over Kozai with 81% confidence. We also assess the number of additional hot star spin-orbit measurements that will likely be necessary to provide a more confident model selection, finding that an additional 20-30 measurements has a >50% chance of resulting in a 95%-confident model selection, if the current model selection is correct. While we test only the predictions of particular Kozai and scattering migration models in this work, our methods may be used to test the predictions of any other spin-orbit misaligning mechanism.Comment: 9 pages, 8 figures, ApJ responded to refere

    A Smaller Radius for the Transiting Exoplanet WASP-10b

    Get PDF
    We present photometry of WASP-10 during the transit of its short-period Jovian planet. We employed the novel PSF-shaping capabilities the OPTIC camera mounted on the UH 2.2m telescope to achieve a photometric precision of 4.7e-4 per 1.3 min sample. With this new light curve, in conjunction with stellar evolutionary models, we improve on existing measurements of the planetary, stellar and orbital parameters. We find a stellar radius Rstar = 0.698 +/- 0.012 Rsun and a planetary radius Rp = 1.080 +/- 0.020 Rjup. The quoted errors do not include any possible systematic errors in the stellar evolutionary models. Our measurement improves the precision of the planet's radius by a factor of 4, and revises the previous estimate downward by 16% (2.5sigma, where sigma is the quadrature sum of the respective confidence limits). Our measured radius of WASP-10b is consistent with previously published theoretical radii for irradiated Jovian planets.Comment: 4 pages, 2 tables, 2 figures, table 1 available upon reques

    Open data and the academy: an evaluation of CKAN for research data management

    Get PDF
    This paper offers a full and critical evaluation of the open source CKAN software (http://ckan.org) for use as a Research Data Management (RDM) tool within a university environment. It presents a case study of CKAN's implementation and use at the University of Lincoln, UK, and highlights its strengths and current weaknesses as an institutional Research Data Management tool. The author draws on his prior experience of implementing a mixed media Digital Asset Management system (DAM), Institutional Repository (IR) and institutional Web Content Management System (CMS), to offer an outline proposal for how CKAN can be used effectively for data analysis, storage and publishing in academia. This will be of interest to researchers, data librarians, and developers, who are responsible for the implementation of institutional RDM infrastructure. This paper is presented as part of the dissemination activities of the Jisc-funded Orbital project (http://orbital.blogs.lincoln.ac.uk

    Inclusive J/psi and psi(2S) production in p-Pb collisions at sqrt(s_NN) = 5.02 TeV with ALICE at the LHC

    Full text link
    We report on the inclusive J/psi nuclear modification factor in p-Pb collisions at sqrt(s_NN) = 5.02 TeV as a function of rapidity y and transverse momentum p_T. The experimental coverage extends down to p_T = 0 GeV/c in the three rapidity ranges accessible by ALICE (-4.46 < y_cms < -2.96, -1.37 < y_cms < 0.46, 2.03 < y_cms < 3.53). The obtained results as a function of rapidity are in agreement with theory predictions based only on shadowing or on coherent energy loss. At forward and backward rapidity, the psi(2S) measurement complements the J/psi results. The ratio between the psi(2S) and J/psi cross section is significantly smaller in p-Pb than in pp collisions in both rapidity regions.Comment: To appear in the proceedings of Hard-Probes 2013, the 6th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions, Nov. 201

    Heavy flavour production in proton-lead and lead-lead collisions with LHCb

    Full text link
    The LHCb experiment offers the unique opportunity to study heavy-ion interactions in the forward region (2 <eta< 5), in a kinematic domain complementary to the other 3 large experiments at the LHC. The detector has excellent capabilities for reconstructing quarkonia and open charm states, including baryons, down to zero pTp_T. It can separate the prompt and displaced charm components. In ppPb collisions, both forward and backward rapidities are covered thanks to the possibility of beam reversal. Results include measurements of the nuclear modification factor and forward-backward ratio for charmonium, open charm and bottomonium states. These quantities are sensitive probes for nuclear effects in heavy flavour production. Perspectives are given with the large accumulated luminosity during the 2016 ppPb run at the LHC. In 2015, LHCb participated successfully for the first time in the PbPb data-taking. The status of the forward prompt J/ψ\psi nuclear modification factor measurement in lead-lead collisions is discussed.Comment: 4 pages, 3 Figures, proceedings for the XXVIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions, Quark Matter 2017 in Chicago from February 5 to February 11, 201

    Hacking in the university: contesting the valorisation of academic labour

    Get PDF
    In this article I argue for a different way of understanding the emergence of hacker culture. In doing so, I outline an account of ‘the university’ as an institution that provided the material and subsequent intellectual conditions that early hackers were drawn to and in which they worked. I argue that hacking was originally a form of academic labour that emerged out of the intensification and valorisation of scientific research within the institutional context of the university. The reproduction of hacking as a form of academic labour took place over many decades as academics and their institutions shifted from an ideal of unproductive, communal science to a more productive, entrepreneurial approach to the production of knowledge. As such, I view hacking as a peculiar, historically situated form of labour that arose out of the contradictions of the academy: vocation vs. profession; teaching vs. research; basic vs. applied research; research vs. development; private vs. public; war vs. peace; institutional autonomy vs. state dependence; scientific communalism vs. intellectual property

    The university as a hackerspace

    Get PDF
    In a paper published last year, I argued for a different way of understanding the emergence of hacker culture. (Winn 2013) In doing so, I outlined an account of ‘the university’ as an institution that provided the material and subsequent intellectual conditions that early hackers were drawn to and in which they worked. The key point I tried to make was that hacking was originally a form of academic labour that emerged out of the intensification and valorisation of scientific research within the institutional context of the university. The reproduction of hacking as a form of academic labour took place over many decades as academics and their institutions shifted from an ideal of unproductive, communal science to a more productive, entrepreneurial approach to the production of knowledge. As such, I view hacking as a peculiar, historically situated form of labour that arose out of friction in the academy: vocation vs. profession; teaching vs. research; basic vs. applied research; research vs. development; private vs. public; war vs. peace; institutional autonomy vs. state dependence; scientific communalism vs. intellectual property; individualism vs. co-operation. A question I have for you today is whether hacking in the university is still a possibility? Can a university contain (i.e. intellectually, politically, practically) a hackerspace? Can a university be a hackerspace? If so, what does it look like? How would it work? I am trying to work through these questions at the moment with colleagues at the University of Lincoln. The name I have given to this emerging project is ‘The university as a hackerspace’ and it has grown out of an existing pedagogical and political project called ‘Student as Producer.’ It is also one of four agreed areas of work in a new ‘digital education’ strategy at Lincoln. More broadly, our project asks “how do we reproduce the university as a critical, social project?
    • 

    corecore