5,912 research outputs found

    Entanglement between living bacteria and quantized light witnessed by Rabi splitting

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    We model recent experiments on living sulphur bacteria interacting with quantised light, using the Dicke model. The strong coupling achieved between the bacteria and the light indicates that during the experiment the bacteria (treated as dipoles) and the quantized light are entangled. The vacuum Rabi splitting, which was measured in the experiment for a range of different parameters, can be used as an entanglement witness

    Testing for Non-Gaussianity in the Wilkinson Microwave Anisotropy Probe Data: Minkowski Functionals and the Length of the Skeleton

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    The three Minkowski functionals and the recently defined length of the skeleton are estimated for the co-added first-year Wilkinson Microwave Anisotropy Probe (WMAP) data and compared with 5000 Monte Carlo simulations, based on Gaussian fluctuations with the a-priori best-fit running-index power spectrum and WMAP-like beam and noise properties. Several power spectrum-dependent quantities, such as the number of stationary points, the total length of the skeleton, and a spectral parameter, gamma, are also estimated. While the area and length Minkowski functionals and the length of the skeleton show no evidence for departures from the Gaussian hypothesis, the northern hemisphere genus has a chi^2 that is large at the 95% level for all scales. For the particular smoothing scale of 3.40 degrees FWHM it is larger than that found in 99.5% of the simulations. In addition, the WMAP genus for negative thresholds in the northern hemisphere has an amplitude that is larger than in the simulations with a significance of more than 3 sigma. On the smallest angular scales considered, the number of extrema in the WMAP data is high at the 3 sigma level. However, this can probably be attributed to the effect of point sources. Finally, the spectral parameter gamma is high at the 99% level in the northern Galactic hemisphere, while perfectly acceptable in the southern hemisphere. The results provide strong evidence for the presence of both non-Gaussian behavior and an unexpected power asymmetry between the northern and southern hemispheres in the WMAP data.Comment: 17 pages, 10 figures, accepted for publication in Ap

    Nonlinear Evolution of the Genus Statistics with Zel'dovich Approximation

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    Evolution of genus density is calculated from Gaussian initial conditions using Zel'dovich approximation. A new approach is introduced which formulates the desired quantity in a rotationally invariant manner. It is shown that normalized genus density does not depend on the initial spectral shape but is a function of the fluctuation amplitude only.Comment: 21 pages, 6 Postscript figures, LaTe

    Computational Study of Turbulent-Laminar Patterns in Couette Flow

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    Turbulent-laminar patterns near transition are simulated in plane Couette flow using an extension of the minimal flow unit methodology. Computational domains are of minimal size in two directions but large in the third. The long direction can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found and studied: periodic, localized, and intermittent. These correspond closely to observations in large aspect ratio experiments.Comment: 4 pages, 5 figure

    A Counts-in-Cells Analysis of Lyman-break Galaxies at z~3

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    We have measured the counts-in-cells fluctuations of 268 Lyman-break galaxies with spectroscopic redshifts in six 9 arcmin by 9 arcmin fields at z~3. The variance of galaxy counts in cubes of comoving side length 7.7, 11.9, 11.4 h^{-1} Mpc is \sigma_{gal}^2 ~ 1.3\pm0.4 for \Omega_M=1, 0.2 open, 0.3 flat, implying a bias on these scales of \sigma_{gal} / \sigma_{mass} = 6.0\pm1.1, 1.9\pm0.4, 4.0\pm0.7. The bias and abundance of Lyman-break galaxies are surprisingly consistent with a simple model of structure formation which assumes only that galaxies form within dark matter halos, that Lyman-break galaxies' rest-UV luminosities are tightly correlated with their dark masses, and that matter fluctuations are Gaussian and have a linear power-spectrum shape at z~3 similar to that determined locally (\Gamma~0.2). This conclusion is largely independent of cosmology or spectral normalization \sigma_8. A measurement of the masses of Lyman-break galaxies would in principle distinguish between different cosmological scenarios.Comment: Accepted for publication in ApJ, 16 pages including 4 figure

    Fluctuation Spectrum from a Scalar-Tensor Bimetric Gravity Theory

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    Predictions of the CMB spectrum from a bimetric gravity theory (gr-qc/0101126) are presented. The initial inflationary period in BGT is driven by a vanishingly small speed of gravitational waves v_g in the very early universe. This initial inflationary period is insensitive to the choice of scalar field potential and initial values of the scalar field. After this initial period of inflation, v_g will increase rapidly and the effects of a potential will become important. We show that a quadratic potential introduced into BGT yields an approximately flat spectrum with inflation parameters: n_s=0.98, n_t=-0.027, alpha_s=-3.2e-4 and alpha_t=-5.0e-4, with r >= 0.014.Comment: 14 pages, uses amsmath, amssym

    Experiments in free shear flows: Status and needs for the future

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    Experiments in free turbulent flows are recommended with the primary concern placed on classical flows in order to augment understanding and for model building. Five classes of experiments dealing with classical free turbulent flows are outlined and proposed as being of particular significance for the near future. These classes include the following: (1) Experiments clarifying the effect of density variation owing to use of different gases, with and without the additional effect of density variation due to high Mach number or other effects; (2) experiments clarifying the role and importance of various parameters which determine the behavior of the near field as well as the condictions under which any of these parameters can be neglected; (3) experiments determining the cumulative effect of initial conditions in terms of distance to fully established flow; (4) experiments for cases where two layers of distinctly different initial turbulence structure flow side by side at the same mean speed; and (5) experiment using contemporary experimental techniques to study structure in free turbulent shear flows in order to compliment and support contemporary work on boundary layers

    Strengths Perspective in Critical Macro Practice: Tentative Guidance for Transformative Strengths-Based Policy, Organizational, and Community Practice

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    This chapter aims to expand both theorizing and application of strengths perspec- tive in policy, organizational, and community contexts across inter-professional settings in human services. It begins with a brief overview of the history of strengths perspective and its pivotal influence on social work, human services, community psychology, community development, and other disciples. It goes on to bring to light traditionally dominant policy, organization, and community practice foundations within interdisciplinary human service practice. By highlighting these historically situated and presently reinforced rational, bureaucratic, and linear approaches; it argues for intentional integration of strengths perspective into macro practice en- vironments. Aligned with early scholars and practitioners that use critical perspec- tives as a foundation for the development of strengths perspective, and who assert its practical efficacy in numerous direct practice settings, it affirms broadening strengths perspective to policy, organizational, and community settings. In the interest of clarity, throughout the chapter, we use the term macro practice to describe human service activities within policy, organizational, and community set- tings (Reisch, 2017). Additionally, following the lead of other scholars in establishing critical community practice (Butcher, Banks, Henderson, & Robertson, 2007; Evans, 2015), many terms we conceive, such as critical strengths-based practice, critical macro practice, critical policy practice, and critical organizational practice. These terms, defined in further sections, differentiate these approaches from their more traditional, rational, and incremental counterparts. Beginning with a brief historical overview of strengths perspective, authors define critical strengths perspective, detail essential elements of critical macro practice, and provide examples of these distinct approaches in practice. The piece offers a critical lens to frame strengths perspective in macro contexts and demonstrates ways in which it can be applied in multiple policies, community, and organizational settings. Concluding with a set of tentative guides and considerations for critical strengths-based practice, such as prefigurative practices, humanization, intersec- tionality, democratic practice, and critical consciousness; we hope it offers tools, opens dialogue among practitioners and scholars, encourages active scholarship in this area, and spurs the necessary flourishing of truly transformative critical strengths-based practice
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