5,362 research outputs found

    Who Loses: An examination of losses in housing net worth, non-housing assets, and total savings from 2007 to 2008 among American families

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    This study models the loss in non-housing assets, increase in non-housing liabilities, and net change in housing value across people by education, ethnic, and occupational categories in the 2007-2008 collapse of Wall Street financial markets. Hypotheses of plausible loci of loss include the usual social categories. Findings do not confirm all of the common presuppositions—managerial class workers have among the largest losses, retirees somewhat limited losses, and losses by educational group decline with advancing education, with the possible exception of Ph.D. holders. The group which had the most severe losses in all asset categories was the armed forces. The magnitude of the suggested effects would indicate that additional policy attention should be targeted on military family outcomes under economic stress.housing net worth; non-household liabilities; non-household assets; occupational group; education level;

    Search for Eccentric Binary Neutron Star Mergers in the first and second observing runs of Advanced LIGO

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    We present a search for gravitational waves from merging binary neutron stars which have non-negligible eccentricity as they enter the LIGO observing band. We use the public Advanced LIGO data which covers the period from 2015 through 2017 and contains 164\sim164 days of LIGO-Hanford and LIGO-Livingston coincident observing time. The search was conducted using matched-filtering using the PyCBC toolkit. We find no significant binary neutron star candidates beyond GW170817, which has previously been reported by searches for binaries in circular orbits. We place a 90% upper limit of 1700\sim1700 mergers Gpc3Yr1\textrm{Gpc}^{-3} \textrm{Yr}^{-1} for eccentricities 0.43\lesssim 0.43 at a dominant-mode gravitational-wave frequency of 10 Hz. The absence of a detection with these data is consistent with theoretical predictions of eccentric binary neutron star merger rates. Using our measured rate we estimate the sensitive volume of future gravitational-wave detectors and compare this to theoretical rate predictions. We find that, in the absence of a prior detection, the rate limits set by six months of Cosmic Explorer observations would constrain all current plausible models of eccentric binary neutron star formation

    Investigating the noise residuals around the gravitational wave event GW150914

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    We use the Pearson cross-correlation statistic proposed by Liu and Jackson, and employed by Creswell et al., to look for statistically significant correlations between the LIGO Hanford and Livingston detectors at the time of the binary black hole merger GW150914. We compute this statistic for the calibrated strain data released by LIGO, using both the residuals provided by LIGO and using our own subtraction of a maximum-likelihood waveform that is constructed to model binary black hole mergers in general relativity. To assign a significance to the values obtained, we calculate the cross-correlation of both simulated Gaussian noise and data from the LIGO detectors at times during which no detection of gravitational waves has been claimed. We find that after subtracting the maximum likelihood waveform there are no statistically significant correlations between the residuals of the two detectors at the time of GW150914.Comment: 14 pages, 7 figures. Minor text and figure changes in final v3. Notebooks for generating the results are available at https://github.com/gwastro/gw150914_investigatio

    Dynamic Normalization for Compact Binary Coalescence Searches in Non-Stationary Noise

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    The output of gravitational-wave interferometers, such as LIGO and Virgo, can be highly non-stationary. Broadband detector noise can affect the detector sensitivity on the order of tens of seconds. Gravitational-wave transient searches, such as those for colliding black holes, estimate this noise in order to identify gravitational-wave events. During times of non-stationarity we see a higher rate of false events being reported. To accurately separate signal from noise, it is imperative to incorporate the changing detector state into gravitational-wave searches. We develop a new statistic which estimates the variation of the interferometric detector noise. We use this statistic to re-rank candidate events identified during LIGO-Virgo's second observing run by the PyCBC search pipeline. This results in a 7% improvement in the sensitivity volume for low mass binaries, particularly binary neutron stars mergers

    Template banks to search for low-mass binary black holes in advanced gravitational-wave detectors

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    Coalescing binary black holes (BBHs) are among the most likely sources for the Laser Interferometer Gravitational-wave Observatory (LIGO) and its international partners Virgo and KAGRA. Optimal searches for BBHs require accurate waveforms for the signal model and effectual template banks that cover the mass space of interest. We investigate the ability of the second-order post-Newtonian TaylorF2 hexagonal template placement metric to construct an effectual template bank, if the template waveforms used are effective one body waveforms tuned to numerical relativity (EOBNRv2). We find that by combining the existing TaylorF2 placement metric with EOBNRv2 waveforms, we can construct an effectual search for BBHs with component masses in the range 3 Msolar <= m_1, m_2 <= 25 Msolar. We also show that the (computationally less expensive) TaylorF2 post-Newtonian waveforms can be used in place of EOBNRv2 waveforms when M <~ 11.4 Msolar. Finally, we investigate the effect of modes other than the dominant l = m = 2 mode in BBH searches. We find that for systems with (m_1/m_2)= 2.68 radians, there is no significant loss in the total possible signal-to-noise ratio due to neglecting modes other than l = m = 2 in the template waveforms. For a source population uniformly distributed in spacial volume, over the entire sampled region of the component-mass space, the loss in detection rate (averaged over a uniform distribution of inclination angle and sky-location/polarization angles), remains below ~11%. For binaries with high mass-ratios \textit{and} 0.31 <= \iota <= 2.68, including higher order modes could increase the signal-to-noise ratio by as much as 8% in Advanced LIGO. Our results can be used to construct matched-filter searches in Advanced LIGO and Advanced Virgo.Comment: 12 pages, 10 figure

    PyCBC Live: Rapid Detection of Gravitational Waves from Compact Binary Mergers

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    We introduce an efficient and straightforward technique for rapidly detecting gravitational waves from compact binary mergers. We show that this method achieves the low latencies required to alert electromagnetic partners of candidate binary mergers, aids in data monitoring, and makes use of multidetector networks for sky localization. This approach was instrumental to the analysis of gravitational-wave candidates during the second observing run of Advanced LIGO, including the period of coincident operation with Advanced Virgo, and in particular the analysis of the first observed binary neutron star merger GW170817, where it led to the first tightly localized sky map (31 deg231~\mathrm{deg}^2) used to identify AT 2017gfo. Operation of this analysis also enabled the initial discovery of GW170104 and GW170608 despite non-nominal observing of the instrument.Comment: 10 pages, 5 figures, submitted to Physical Review

    AVALIAÇÃO DA EDUCAÇÃO SUPERIOR E A GESTÃO UNIVERSITÁRIA: PADRÕES DE QUALIDADE DEFINIDOS PELAS INSTITUIÇÕES DE ENSINO SUPERIOR, PELO MEC E PELA SOCIEDADE, INCLUINDO ENADE, IDD, CPC E IGC.

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    Este artigo, elaborado a partir de uma pesquisa bibliográfica, aborda a expansão desenfreada do ensino superior brasileiro, especialmente o segmento das Instituições de Ensino Superior privadas, que tem levado a um intenso acirramento da concorrência entre as Instituições de Ensino Superior além de uma crescente preocupação para a Sociedade e para o Governo, sobre a garantia de padrões de qualidade para este importante segmento. Primeiramente é discutida a definição do conceito de qualidade em ensino superior, a seguir é feita uma análise crítica dos principais indicadores de qualidade instituídos pelo governo e sua eficiência em medi-la. Na sequência, o papel das Comissões Próprias de Avaliação — CPAs —é destacado nesse contexto. Por fim, o trabalho apresenta possíveis estratégias de gestão das IES nesse contexto de grande competitividade e pressão regulatória
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