15,369 research outputs found

    Non-parametric Cosmology with Cosmic Shear

    Get PDF
    We present a method to measure the growth of structure and the background geometry of the Universe -- with no a priori assumption about the underlying cosmological model. Using Canada-France-Hawaii Lensing Survey (CFHTLenS) shear data we simultaneously reconstruct the lensing amplitude, the linear intrinsic alignment amplitude, the redshift evolving matter power spectrum, P(k,z), and the co-moving distance, r(z). We find that lensing predominately constrains a single global power spectrum amplitude and several co-moving distance bins. Our approach can localise precise scales and redshifts where Lambda-Cold Dark Matter (LCDM) fails -- if any. We find that below z = 0.4, the measured co-moving distance r (z) is higher than that expected from the Planck LCDM cosmology by ~1.5 sigma, while at higher redshifts, our reconstruction is fully consistent. To validate our reconstruction, we compare LCDM parameter constraints from the standard cosmic shear likelihood analysis to those found by fitting to the non-parametric information and we find good agreement.Comment: 13 pages. Matches PRD accepted versio

    Measuring eccentricity in binary black-hole initial data

    Full text link
    Initial data for evolving black-hole binaries can be constructed via many techniques, and can represent a wide range of physical scenarios. However, because of the way that different schemes parameterize the physical aspects of a configuration, it is not alway clear what a given set of initial data actually represents. This is especially important for quasiequilibrium data constructed using the conformal thin-sandwich approach. Most initial-data studies have focused on identifying data sets that represent binaries in quasi-circular orbits. In this paper, we consider initial-data sets representing equal-mass black holes binaries in eccentric orbits. We will show that effective-potential techniques can be used to calibrate initial data for black-hole binaries in eccentric orbits. We will also examine several different approaches, including post-Newtonian diagnostics, for measuring the eccentricity of an orbit. Finally, we propose the use of the ``Komar-mass difference'' as a useful, invariant means of parameterizing the eccentricity of relativistic orbits.Comment: 12 pages, 11 figures, submitted to Physical Review D, revtex

    Matrix elements and duality for type 2 unitary representations of the Lie superalgebra gl(m|n)

    Get PDF
    The characteristic identity formalism discussed in our recent articles is further utilized to derive matrix elements of type 2 unitary irreducible gl(m∣n)gl(m|n) modules. In particular, we give matrix element formulae for all gl(m|n) generators, including the non-elementary generators, together with their phases on finite dimensional type 2 unitary irreducible representations. Remarkably, we find that the type 2 unitary matrix element equations coincide with the type 1 unitary matrix element equations for non-vanishing matrix elements up to a phase.Comment: 24 pages. arXiv admin note: text overlap with arXiv:1311.424

    Reduced Wigner coefficients for Lie superalgebra gl(m|n) corresponding to unitary representations and beyond

    Full text link
    In this paper fundamental Wigner coefficients are determined algebraically by considering the eigenvalues of certain generalized Casimir invariants. Here this method is applied in the context of both type 1 and type 2 unitary representations of the Lie superalgebra gl(mjn). Extensions to the non-unitary case are investigated. A symmetry relation between two classes of Wigner coefficients is given in terms of a ratio of dimensions.Comment: 17 page

    Combining community-based research and local knowledge to confront asthma and subsistence-fishing hazards in Greenpoint/Williamsburg, Brooklyn, New York.

    Get PDF
    Activists in the environmental justice movement are challenging expert-driven scientific research by taking the research process into their own hands and speaking for themselves by defining, analyzing, and prescribing solutions for the environmental health hazards confronting communities of the poor and people of color. I highlight the work of El Puente and The Watchperson Project--two community-based organizations in the Greenpoint/Williamsburg neighborhood in Brooklyn, New York, that have engaged in community-based participatory research (CBPR) to address asthma and risks from subsistence-fish diets. The CBPR process aims to engage community members as equal partners alongside scientists in problem definition, information collection, and data analysis--all geared toward locally relevant action for social change. In the first case I highlight how El Puente has organized residents to conduct a series of asthma health surveys and tapped into local knowledge of the Latino population to understand potential asthma triggers and to devise culturally relevant health interventions. In a second case I follow The Watchperson Project and their work surveying subsistence anglers and note how the community-gathered information contributed key data inputs for the U.S. Environmental Protection Agency Cumulative Exposure Project in the neighborhood. In each case I review the processes each organization used to conduct CBPR, some of their findings, and the local knowledge they gathered, all of which were crucial for understanding and addressing local environmental health issues. I conclude with some observations about the benefits and limits of CBPR for helping scientists and communities pursue environmental justice

    GNSS Signal Authentication via Power and Distortion Monitoring

    Get PDF
    We propose a simple low-cost technique that enables civil Global Positioning System (GPS) receivers and other civil global navigation satellite system (GNSS) receivers to reliably detect carry-off spoofing and jamming. The technique, which we call the Power-Distortion detector, classifies received signals as interference-free, multipath-afflicted, spoofed, or jammed according to observations of received power and correlatio n function distortion. It does not depend on external hardware or a network connection and can be readily implemented on many receivers via a firmware update. Crucially, the detector can with high probability distinguish low-power spoofing from ordinary multipath. In testing against over 25 high-quality empirical data sets yielding over 900,000 separate detection tests, the detector correctly alarms on all malicious spoofing or jamming attack s while maintaining a <0.5% single-channel false alarm rate.Aerospace Engineering and Engineering Mechanic

    Higgs Boson Exempt No-Scale Supersymmetry and its Collider and Cosmology Implications

    Get PDF
    One of the most straightforward ways to address the flavor problem of low-energy supersymmetry is to arrange for the scalar soft terms to vanish simultaneously at a scale McM_{c} much larger than the electroweak scale. This occurs naturally in a number of scenarios, such as no-scale models, gaugino mediation, and several models with strong conformal dynamics. Unfortunately, the most basic version of this approach that incorporates gaugino mass unification and zero scalar masses at the grand unification scale is not compatible with collider and dark matter constraints. However, experimental constraints can be satisfied if we exempt the Higgs bosons from flowing to zero mass value at the high scale. We survey the theoretical constructions that allow this, and investigate the collider and dark matter consequences. A generic feature is that the sleptons are relatively light. Because of this, these models frequently give a significant contribution to the anomalous magnetic moment of the muon, and neutralino-slepton coannihilation can play an important role in obtaining an acceptable dark matter relic density. Furthermore, the light sleptons give rise to a large multiplicity of lepton events at colliders, including a potentially suggestive clean trilepton signal at the Tevatron, and a substantial four lepton signature at the LHC.Comment: 36 pages, 16 figure
    • …
    corecore