635 research outputs found

    Committee Socialization in the U. S. House of Representatives

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    Book Review: Political Organizations by James Q. Wilson

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    The American Religious Landscape and the 2004 Presidential Vote: Increased Polarization

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    Presents findings from a post-election survey conducted in November and December 2004. Explores the polarization between different religions, as well as within the major religious traditions

    Religion and American Public Attitudes on War and Peace

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    In recent years, scholars have discovered that the American public responds to foreign policy issues on the basis of fairly stable broad orientations toward international affairs, influenced by a number of demographic, ideological, and partisan factors. Although there has been much recent speculation about the role that religion plays in shaping such orientations, there are very few empirical analyses of that influence. In this article, I use the 2012 Chicago Council on Global Affairs survey to classify American religious groups on Wittkopf s (1990) classic dimensions of foreign policy attitudes: militant internationalism and cooperative internationalism. I find rather different religious constituencies for each perspective, with Evangelical Protestants and religious traditionalists from other faiths most supportive of militant internationalism, while ethnoreligious minorities and religious modernists are most likely to back cooperative internationalism

    Devaluation: a dynamical mechanism for a naturally small cosmological constant

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    We propose a natural solution to the cosmological constant problem consistent with the standard cosmology and successful over a broad range of energies. This solution is based on the existence of a new field, the devaluton, with its potential modeled on a tilted cosine. After inflation, the universe reheats and populates the devaluton's many minima. As the universe cools, domain walls form between different regions. The domain wall network then evolves and sweeps away regions of higher vacuum energy in favor of lower energy ones. Gravitation itself provides a cutoff at a minimum vacuum energy, thus leaving the universe with a small cosmological constant comparable in magnitude to the present day dark energy density.Comment: 6 pages and prepared in ReV-TeX added notes on eltro-weak breaking and ds vacu

    Observing the Inflaton Potential

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    We show how observations of the density perturbation (scalar) spectrum and the gravitational wave (tensor) spectrum allow a reconstruction of the potential responsible for cosmological inflation. A complete functional reconstruction or a perturbative approximation about a single scale are possible; the suitability of each approach depends on the data available. Consistency equations between the scalar and tensor spectra are derived, which provide a powerful signal of inflation.Comment: 9 pages, LaTeX, FERMILAB--PUB--93/071--A; SUSSEX-AST 93/4-

    Non-Gaussian gravitational clustering field statistics

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    In this work we investigate the multivariate statistical description of the matter distribution in the nonlinear regime. We introduce the multivariate Edgeworth expansion of the lognormal distribution to model the cosmological matter field. Such a technique could be useful to generate and reconstruct three-dimensional nonlinear cosmological density fields with the information of higher order correlation functions. We explicitly calculate the expansion up to third order in perturbation theory making use of the multivariate Hermite polynomials up to sixth order. The probability distribution function for the matter field includes at this level the two-point, the three-point and the four-point correlation functions. We use the hierarchical model to formulate the higher order correlation functions based on combinations of the two-point correlation function. This permits us to find compact expressions for the skewness and kurtosis terms of the expanded lognormal field which can be efficiently computed. The method is, however, flexible to incorporate arbitrary higher order correlation functions which have analytical expressions. The applications of such a technique can be especially useful to perform weak-lensing or neutral hydrogen 21 cm line tomography, as well as to directly use the galaxy distribution or the Lyman-alpha forest to study structure formation.Comment: 20 pages, 2 figures; accepted in MNRAS 2011 August 22, in original form 2010 December 14 published, Publication Date: 03/201

    Topology of non-linear structure in the 2dF Galaxy Redshift Survey

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    We study the evolution of non-linear structure as a function of scale in samples from the 2dF Galaxy Redshift Survey, constituting over 221 000 galaxies at a median redshift of z=0.11. The two flux-limited galaxy samples, located near the southern galactic pole and the galactic equator, are smoothed with Gaussian filters of width ranging from 5 to 8 Mpc/h to produce a continuous galaxy density field. The topological genus statistic is used to measure the relative abundance of overdense clusters to void regions at each scale; these results are compared to the predictions of analytic theory, in the form of the genus statistic for i) the linear regime case of a Gaussian random field; and ii) a first-order perturbative expansion of the weakly non-linear evolved field. The measurements demonstrate a statistically significant detection of an asymmetry in the genus statistic between regions corresponding to low- and high-density volumes of the universe. We attribute the asymmetry to the non-linear effects of gravitational evolution and biased galaxy formation, and demonstrate that these effects evolve as a function of scale. We find that neither analytic prescription satisfactorily reproduces the measurements, though the weakly non-linear theory yields substantially better results in some cases, and we discuss the potential explanations for this result.Comment: 13 pages, matching proof to be published in MNRAS; new version adds reference and corrects figure

    Effective number of neutrinos and baryon asymmetry from BBN and WMAP

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    We place constraints on the number of relativistic degrees of freedom and on the baryon asymmetry at the epoch of Big Bang Nucleosynthesis (BBN) and at recombination, using cosmic background radiation (CBR) data from the Wilkinson Microwave Anisotropy Probe (WMAP), complemented by the Hubble Space Telescope (HST) Key Project measurement of the Hubble constant, along with the latest compilation of deuterium abundances and measurements of the primordial helium abundance. The agreement between the derived values of these key cosmological and particle physics parameters at these widely separated (in time or redshift) epochs is remarkable. From the combination of CBR and BBN data, we find the 2\sigma ranges for the effective number of neutrinos and for the baryon asymmetry (baryon to photon number ratio \eta) to be 1.7-3.0 and 5.53-6.76 \times 10^{-10}, respectively.Comment: 10 pages, 10 figures, 2 table
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