32,514 research outputs found

    A reciprocal Wald theorem for varying gravitational function

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    We study when a cosmological constant is a natural issue if it is mimicked by the potential of a massive Hyperextended Scalar Tensor theory with a perfect fluid for Bianchi type I and V models. We then deduce a reciprocal Wald theorem giving the conditions such that the potential tends to a non vanishing constant when the gravitational function varies. We also get the conditions allowing the potentiel to vanish or diverge.Comment: 13 page

    The Foundation Performance Dashboard: Vital Statistics for Social Impact

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    Boards and foundation leadership rarely have a clear, consistent, and comprehensive picture of their foundation's performance. Interestingly, this situation persists despite the fact that nearly 60% of foundation CEOs would like to have more board involvement in reviewing the foundation's philanthropic mission and effectiveness. Our experience suggests that this conundrum results from a fundamental uncertainty: Foundations are unsure how to bridge the chasm between the readily available and concise metrics for investment performance and the much more complex, expensive, and subjective data from internal operations and program evaluations

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    Cybersocialism. Group Consciousness in Transnational Communities

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    An important new type of community is emerging with the rapid advances in communication technologies: communities that cross cultural and political boundaries to engage in a commerce of information exchange. While there has been much research focused on the technological development of computersupported collaborative work, less is known about sociocultural attitudes and an understanding of how people perceive “belongingness” to a community in an environment where interaction is mediated by shared computer resources

    A coupled vacuum energy model producing endless alternated phases of accelerated and decelerated expansion

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    We consider a flat Universe filled with a vacuum energy coupled to matter and radiation by respectively positive coupling functions QmQ_m and QrQ_r. We require that these functions be such as Universe exits from inflation to go to a radiation dominated epoch and allow to reproduce the observed ΛCDM\Lambda CDM expansion after this last epoch. These requirements lead to some necessary constraints on the coupling functions. We then look at one of the simplest forms of QmQ_m and QrQ_r able to satisfy them. The cosmological model thus defined describes a Universe with an initial singularity and endless alternated periods of accelerated and decelerated expansion (one of them being our ΛCDM\Lambda CDM Universe) unifying inflation and present time expansion acceleration.Comment: 18 pages, 10 figur
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