618 research outputs found

    Facilitators and barriers to contact between asylum seekers and their Dutch neighbors

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    Currently, Europe is dealing with a large number of asylum seekers. A recent report show that attitudes toward asylum seekers are not that negative in the Netherlands, and yet Dutch citizens living close to asylum seeker centers barely have contact with them. Because contact is vital for a multicultural society, we investigated the facilitators and barriers for Dutch citizens to establish and maintain contact with asylum seekers where they live close together. We conducted semistructured interviews with Dutch people and analyzed them using thematic analysis. We found four themes: Physical possibilities for Contact, Goals for Contact, Social Identities, and Positivity and Openness, and proposed a grounded theory model based on how the themes are related. The findings are discussed in relation to debates on multiculturalism and intergroup tolerance, and can be used to improve the integration policies by local governments, because they present clear conditions and practical information as to how contact can be established and maintained

    Reconstructing the Equation of State of Tachyon

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    Recent progress in theoretical physics suggests that the dark energy in the universe might be resulted from the rolling tachyon field of string theory. Measurements to SNe Ia can be helpful to reconstruct the equation of state of the rolling tachyon which is a possible candidate of dark energy. We present a numerical analysis for the evolution of the equation of state of the rolling tachyon and derive the reconstruction equations for the equation of state as well as the potential.Comment: 6 pages, 3 figures, to appear Phys. Rev.

    Gravity and Electromagnetism with Y(R)F2Y(R)F^2-type Coupling and Magnetic Monopole Solutions

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    We investigate Y(R)F2 Y(R) F^2 -type coupling of electromagnetic fields to gravity. After we derive field equations by a first order variational principle from the Lagrangian formulation of the non-minimally coupled theory, we look for static, spherically symmetric, magnetic monopole solutions. We point out that the solutions can provide possible geometries which may explain the flatness of the observed rotation curves of galaxies.Comment: 10 page

    Observational Constraints on Chaplygin Quartessence: Background Results

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    We derive the constraints set by several experiments on the quartessence Chaplygin model (QCM). In this scenario, a single fluid component drives the Universe from a nonrelativistic matter-dominated phase to an accelerated expansion phase behaving, first, like dark matter and in a more recent epoch like dark energy. We consider current data from SNIa experiments, statistics of gravitational lensing, FR IIb radio galaxies, and x-ray gas mass fraction in galaxy clusters. We investigate the constraints from this data set on flat Chaplygin quartessence cosmologies. The observables considered here are dependent essentially on the background geometry, and not on the specific form of the QCM fluctuations. We obtain the confidence region on the two parameters of the model from a combined analysis of all the above tests. We find that the best-fit occurs close to the Λ\LambdaCDM limit (α=0\alpha=0). The standard Chaplygin quartessence (α=1\alpha=1) is also allowed by the data, but only at the 2σ\sim2\sigma level.Comment: Replaced to match the published version, references update

    Particle Physics Approach to Dark Matter

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    We review the main proposals of particle physics for the composition of the cold dark matter in the universe. Strong axion contribution to cold dark matter is not favored if the Peccei-Quinn field emerges with non-zero value at the end of inflation and the inflationary scale is superheavy since, under these circumstances, it leads to unacceptably large isocurvature perturbations. The lightest neutralino is the most popular candidate constituent of cold dark matter. Its relic abundance in the constrained minimal supersymmetric standard model can be reduced to acceptable values by pole annihilation of neutralinos or neutralino-stau coannihilation. Axinos can also contribute to cold dark matter provided that the reheat temperature is adequately low. Gravitinos can constitute the cold dark matter only in limited regions of the parameter space. We present a supersymmetric grand unified model leading to violation of Yukawa unification and, thus, allowing an acceptable b-quark mass within the constrained minimal supersymmetric standard model with mu>0. The model possesses a wide range of parameters consistent with the data on the cold dark matter abundance as well as other phenomenological constraints. Also, it leads to a new version of shifted hybrid inflation.Comment: 32 pages including 6 figures, uses svmult.cls, some clarifications added, lectures given at the Third Aegean Summer School "The Invisible Universe: Dark Matter and Dark Energy", 26 September-1 October 2005, Karfas, Island of Chios, Greece (to appear in the proceedings

    Can induced gravity isotropize Bianchi I, V, or IX Universes?

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    We analyze if Bianchi I, V, and IX models in the Induced Gravity (IG) theory can evolve to a Friedmann--Roberson--Walker (FRW) expansion due to the non--minimal coupling of gravity and the scalar field. The analytical results that we found for the Brans-Dicke (BD) theory are now applied to the IG theory which has ω1\omega \ll 1 (ω\omega being the square ratio of the Higgs to Planck mass) in a cosmological era in which the IG--potential is not significant. We find that the isotropization mechanism crucially depends on the value of ω\omega. Its smallness also permits inflationary solutions. For the Bianch V model inflation due to the Higgs potential takes place afterwads, and subsequently the spontaneous symmetry breaking (SSB) ends with an effective FRW evolution. The ordinary tests of successful cosmology are well satisfied.Comment: 24 pages, 5 figures, to be published in Phys. Rev. D1

    A systematic review of maternal smoking during pregnancy and fetal measurements with meta-analysis

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    Background Maternal smoking during pregnancy is linked to reduced birth weight but the gestation at onset of this relationship is not certain. We present a systematic review of the literature describing associations between maternal smoking during pregnancy and ultrasound measurements of fetal size, together with an accompanying meta-analysis. Methods Studies were selected from electronic databases (OVID, EMBASE and Google Scholar) that examined associations between maternal smoking or smoke exposure and antenatal fetal ultrasound measurements. Outcome measures were first, second or third trimester fetal measurements. Results There were 284 abstracts identified, 16 papers were included in the review and the metaanalysis included data from eight populations. Maternal smoking was associated with reduced second trimester head size (mean reduction 0.09 standard deviation (SD) [95% CI 0.01, 0.16]) and femur length (0.06 [0.01, 0.10]) and reduced third trimester head size (0.18SD [0.13, 0.23]), femur length (0.27 SD [0.21, 0.32]) and estimated fetal weight (0.18 SD [0.11, 0.24]). Higher maternal cigarette consumption was associated with a lower z score for head size in the second (mean difference 0.09 SD [0, 0.19]) and third (0.15 SD [0.03, 0.26]) trimesters compared to lower consumption. Fetal measurements were not reduced for those whose mothers quit before or after becoming pregnant compared to mothers who had never smoked. Conclusions Maternal smoking during pregnancy is associated with reduced fetal measurements after the first trimester, particularly reduced head size and femur length. These effects may be attenuated if mothers quit or reduce cigarette consumption during pregnancy
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