14,804 research outputs found

    Angular Power Spectra with Finite Counts

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    Angular anisotropy techniques for cosmic diffuse radiation maps are powerful probes, even for quite small data sets. A popular observable is the angular power spectrum; we present a detailed study applicable to any unbinned source skymap S(n) from which N random, independent events are observed. Its exact variance, which is due to the finite statistics, depends only on S(n) and N; we also derive an unbiased estimator of the variance from the data. First-order effects agree with previous analytic estimates. Importantly, heretofore unidentified higher-order effects are found to contribute to the variance and may cause the uncertainty to be significantly larger than previous analytic estimates---potentially orders of magnitude larger. Neglect of these higher-order terms, when significant, may result in a spurious detection of the power spectrum. On the other hand, this would indicate the presence of higher-order spatial correlations, such as a large bispectrum, providing new clues about the sources. Numerical simulations are shown to support these conclusions. Applying the formalism to an ensemble of Gaussian-distributed skymaps, the noise-dominated part of the power spectrum uncertainty is significantly increased at high multipoles by the new, higher-order effects. This work is important for harmonic analyses of the distributions of diffuse high-energy gamma-rays, neutrinos, and charged cosmic rays, as well as for populations of sparse point sources such as active galactic nuclei.Comment: 27 pages, 8 figure

    Computation of Superpotentials for D-Branes

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    We present a general method for the computation of tree-level superpotentials for the world-volume theory of B-type D-branes. This includes quiver gauge theories in the case that the D-brane is marginally stable. The technique involves analyzing the A-infinity structure inherent in the derived category of coherent sheaves. This effectively gives a practical method of computing correlation functions in holomorphic Chern-Simons theory. As an example, we give a more rigorous proof of previous results concerning 3-branes on certain singularities including conifolds. We also provide a new example.Comment: 28 page

    The Galactic Isotropic γ\gamma-ray Background and Implications for Dark Matter

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    We present an analysis of the radial angular profile of the galacto-isotropic (GI) γ\gamma-ray flux--the statistically uniform flux in circular annuli about the Galactic center. Two different approaches are used to measure the GI flux profile in 85 months of Fermi-LAT data: the BDS statistic method which identifies spatial correlations, and a new Poisson ordered-pixel method which identifies non-Poisson contributions. Both methods produce similar GI flux profiles. The GI flux profile is well-described by an existing model of bremsstrahlung, π0\pi^0 production, inverse Compton scattering, and the isotropic background. Discrepancies with data in our full-sky model are not present in the GI component, and are therefore due to mis-modeling of the non-GI emission. Dark matter annihilation constraints based solely on the observed GI profile are close to the thermal WIMP cross section below 100 GeV, for fixed models of the dark matter density profile and astrophysical γ\gamma-ray foregrounds. Refined measurements of the GI profile are expected to improve these constraints by a factor of a few.Comment: 20 pages, 15 figures, references adde

    For the good of the group? Exploring group-level evolutionary adaptations using multilevel selection theory.

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    In this paper, we present an evolutionary framework, multilevel selection theory (MLS), that is highly amenable to existing social psychological theory and empiricism. MLS provides an interpretation of natural selection that shows how group-beneficial traits can evolve, a prevalent implication of social psychological data. We outline the theory and provide a number of example topics, focusing on prosociality, policing behavior, gossip, brainstorming, distributed cognition, and social identity. We also show that individual differences can produce important group-level outcomes depending on differential aggregation of individual types and relate this to the evolutionary dynamics underlying group traits. Drawing on existing work, we show how social psychologists can integrate this framework into their research program and suggest future directions for research

    Routine administration of Health Related Quality of Life (HRQoL) and needs assessment instruments to improve psychological outcome: a systematic review

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    Background. Routine administration of Health Related Quality of Life (HRQoL) and needs assessment instruments has been advocated as part of clinical care to aid the recognition of psychosocial problems, to inform clinical decision making, to monitor therapeutic response and to facilitate patient-doctor communication. However, their adoption is not without cost and the benefit of their use is unclear. Method. A systematic review was conducted. We sought experimental studies that examined the addition of routinely administered measures of HRQoL to care in both psychiatric and non-psychiatric settings. We searched the following databases: MEDLINE, EMBASE, CINAHL, PsycLIT and Cochrane Controlled Trials Register (to 2000). Data were extracted independently and a narrative synthesis of results was presented. Results. Nine randomized and quasi-randomized studies conducted in non-psychiatric settings were found. All the instruments used included an assessment of mental well-being, with specific questions relating to depression and anxiety. The routine feedback of these instruments had little impact on the recognition of mental disorders or on longer term psychosocial functioning. While clinicians welcomed the information these instruments imparted, their results were rarely incorporated into routine clinical decision making. No studies were found that examined the value of routine assessment and feedback of HRQoL or patient needs in specialist psychiatric care settings. Conclusions. Routine HRQoL measurement is a costly exercise and there is no robust evidence to suggest that it is of benefit in improving psychosocial outcomes of patients managed in non-psychiatric settings. Major policy initiatives to increase the routine collection and use of outcome measures in psychiatric settings are unevaluated

    Routinely administered questionnaires for depression and anxiety : systematic review

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    Objectives To examine the effect of routinely administered psychiatric questionnaires on the recognition, management, and outcome of psychiatric disorders in non-psychiatric settings. Data sources Embase, Medline, PsycLIT, Cinahl, Cochrane Controlled Trials Register,and hand searches of key journals. Methods A systematic review of randomised controlled trials of the administration and routine feedback of psychiatric screening and outcome questionnaires to clinicians in non-psychiatric settings. narrative overview of key design features and end points, together with a random effects quantitative synthesis of comparable studies. Main outcome measures Recognition of psychiatric disorders after feedback of questionnaire results; interventions for psychiatric disorders and outcome of psychiatric disorders. Results Nine randomised studies were identified that examined the use of common psychiatric instruments in primary care and general hospital settings. Studies compared the effect of the administration of these instruments followed by the feedback of the results to clinicians, with administration with no feedback. Meta-analytic pooling was possible for four of these studies (2457 participants), which measured the effect of feedback on the recognition of depressive disorders. Routine administration and feedback of scores for all patients (irrespective of score) did not increase the overall rate of recognition of mental disorders such as anxiety and depression (relative risk of detection of depression by clinician after feedback 0.95, 95% confidence interval 0.83 to 1.09). Two studies showed that routine administration followed by selective feedback for only high scores increased the rate of recognition of depression (relative risk of detection of depression after feedback 2.64, 1.62 to 4.31). This increased recognition, however, did not translate into an increased rate of intervention. Overall, studies of routine administration of psychiatric measures did not show an effect on patient outcome. Conclusions The routine measurement of outcome is a costly exercise. Little evidence shows that it is of benefit in improving psychosocial outcomes of those with psychiatric disorder managed in non-psychiatric settings

    Dark matter indirect detection signals and the nature of neutrinos in the supersymmetric U(1)B−LU(1)_{B-L} extension of the standard model

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    In this paper, we study the prospects for determining the nature of neutrinos in the context of a supersymmetric B−LB-L extension of the standard model by using dark matter indirect detection signals and bounds on NeffN_{\text{eff}} from the cosmic microwave background data. The model contains two new dark matter candidates whose dominant annihilation channels produce more neutrinos than neutralino dark matter in the minimal supersymmetric standard model. The photon and neutrino counts may then be used to discriminate between the two models. If the dark matter comes from the B-L sector, its indirect signals and impact on the cosmic microwave background can shed light on the nature of the neutrinos. When the light neutrinos are of Majorana type, the indirect neutrino signal from the Sun and the galactic center may show a prompt neutrino box-feature, as well as an earlier cut-off in both neutrino and gamma ray energy spectra. When the light neutrinos are of Dirac type, their contribution to the effective number of neutrinos NeffN_{\text{eff}} is at a detectable level.Comment: 11 pages, 3 figures, 2 table
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