118 research outputs found

    Numerical computation of real or complex elliptic integrals

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    Algorithms for numerical computation of symmetric elliptic integrals of all three kinds are improved in several ways and extended to complex values of the variables (with some restrictions in the case of the integral of the third kind). Numerical check values, consistency checks, and relations to Legendre's integrals and Bulirsch's integrals are included

    Adjustment studies in self-consistent relativistic mean-field models

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    We investigate the influence of the adjustment procedure and the set of measured observables on the properties and predictive power of relativistic self-consistent mean-field models for the nuclear ground state. These studies are performed with the point-coupling variant of the relativistic mean-field model. We recommend optimal adjustment algorithms for the general two-part problem and we identify various trends and dependencies as well as deficiencies of current models. Consequences for model improvements are presented.Comment: 18 pages, 6 figures, revised version, accepted for publication in Nuclear Physics

    3D/2D registration via skeletal near projective invariance in tubular objects

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    Propagation and Structure of Planar Streamer Fronts

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    Streamers often constitute the first stage of dielectric breakdown in strong electric fields: a nonlinear ionization wave transforms a non-ionized medium into a weakly ionized nonequilibrium plasma. New understanding of this old phenomenon can be gained through modern concepts of (interfacial) pattern formation. As a first step towards an effective interface description, we determine the front width, solve the selection problem for planar fronts and calculate their properties. Our results are in good agreement with many features of recent three-dimensional numerical simulations. In the present long paper, you find the physics of the model and the interfacial approach further explained. As a first ingredient of this approach, we here analyze planar fronts, their profile and velocity. We encounter a selection problem, recall some knowledge about such problems and apply it to planar streamer fronts. We make analytical predictions on the selected front profile and velocity and confirm them numerically. (abbreviated abstract)Comment: 23 pages, revtex, 14 ps file

    Does Solar Physics Provide Constraints to Weakly Interacting Massive Particles?

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    We investigate whether present data on helioseismology and solar neutrino fluxes may constrain WIMP--matter interactions in the range of WIMP parameters under current exploration in WIMP searches. We find that, for a WIMP mass of 30 GeV, once the effect of the presence of WIMPs in the Sun's interior is maximized, the squared isothermal sound speed is modified, with respect to the standard solar model, by at most 0.4% at the Sun's center. The maximal effect on the Boron-8 solar neutrino flux is a reduction of 4.5%. Larger masses lead to smaller effects. These results imply that present sensitivities in the measurements of solar properties, though greatly improved in recent years, do not provide information or constraints on WIMP properties of relevance for dark matter. Furthermore, we show that, when current bounds from direct WIMP searches are taken into account, the effect induced by WIMPs with dominant coherent interactions are drastically reduced as compared to the values quoted above. The case of neutralinos in the minimal supersymmetric standard model is also discussed.Comment: 31 pages, 2 tables and 9 figures, typeset with ReVTeX4. The paper may also be found at http://www.to.infn.it/~fornengo/papers/helio.ps.gz or through http://www.to.infn.it/astropart/index.htm

    A complete 3D numerical study of the effects of pseudoscalar-photon mixing on quasar polarizations

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    We present the results of three-dimensional simulations of quasar polarizations in the presence of pseudoscalar-photon mixing in the intergalactic medium. The intergalactic magnetic field is assumed to be uncorrelated in wave vector space but correlated in real space. Such a field may be obtained if its origin is primordial. Furthermore we assume that the quasars, located at cosmological distances, have negligible initial polarization. In the presence of pseudoscalar-photon mixing we show, through a direct comparison with observations, that this may explain the observed large scale alignments in quasar polarizations within the framework of big bang cosmology. We find that the simulation results give a reasonably good fit to the observed data.Comment: 15 pages, 8 figures, significant changes, to appear in EPJ

    ASEAN and the Dynamics of Resistance to Sovereignty Violation:The Case of the Third Indochina War (1978–1991)

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    This article investigates the history of ASEAN’s relationship to external intervention in regional affairs. It addresses a specific question: What was the basic cause of the success of ASEAN resistance to the Vietnamese challenge to ASEAN’s sovereignty from 1978-1991? ASEAN’s history is understood in terms of a realist theoretical logic, in terms of the relationship between an ASEAN state with the most compelling interests at stake in a given issue, which I call a ‘vanguard state,’ and selected external powers. Using the Third Indochina War (1978–1991) as a case study, this article contends that ASEAN’s ability to resist violations to the sovereignty of Thailand from a Soviet-backed Vietnam is a consequence of high interest convergence between Thailand, and a designated external power, China

    Freedom and constraints in the K3 landscape

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    We consider ``magnetized brane'' compactifications of the type I/heterotic string on K3 with U(1) background fluxes. The gauge group and matter content of the resulting six-dimensional vacua are parameterized by a matrix encoding a lattice contained within the even, self-dual lattice Γ[superscript 3,19]. Mathematical results of Nikulin on lattice embeddings make possible a simple classification of all such solutions. We find that every six-dimensional theory parameterized in this way by a negative semi-definite matrix whose trace satisfies a simple tadpole constraint can be realized as a K3 compactification. This approach makes it possible to explicitly and efficiently construct all models in this class with any particular allowed gauge group and matter content, so that one can immediately ``dial-a-model'' with desired properties

    Tension between SN and BAO: current status and future forecasts

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    Using real and synthetic Type Ia SNe (SNeIa) and baryon acoustic oscillations (BAO) data representing current observations forecasts, this paper investigates the tension between those probes in the dark energy equation of state (EoS) reconstruction considering the well known CPL model and Wang's low correlation reformulation. In particular, here we present simulations of BAO data from both the the radial and transverse directions. We also explore the influence of priors on Omega_m and Omega_b on the tension issue, by considering 1-sigma deviations in either one or both of them. Our results indicate that for some priors there is no tension between a single dataset (either SNeIa or BAO) and their combination (SNeIa+BAO). Our criterion to discern the existence of tension (sigma-distance) is also useful to establish which is the dataset with most constraining power; in this respect SNeIa and BAO data switch roles when current and future data are considered, as forecasts predict and spectacular quality improvement on BAO data. We also find that the results on the tension are blind to the way the CPL model is addressed: there is a perfect match between the original formulation and that by the low correlation optimized, but the errors on the parameters are much narrower in all cases of our exhaustive exploration, thus serving the purpose of stressing the convenience of this reparametrization.Comment: 21 pages, under review in JCA

    The integrated Sachs-Wolfe Effect -- Large Scale Structure Correlation

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    We discuss the correlation between late-time integrated Sachs-Wolfe (ISW) effect in the cosmic microwave background (CMB) temperature anisotropies and the large scale structure of the local universe. This correlation has been proposed and studied in the literature as a probe of the dark energy and its physical properties. We consider a variety of large scale structure tracers suitable for a detection of the ISW effect via a cross-correlation. In addition to luminous sources, we suggest the use of tracers such as dark matter halos or galaxy clusters. A suitable catalog of mass selected halos for this purpose can be constructed with upcoming wide-field lensing and Sunyaev-Zel'dovich (SZ) effect surveys. With multifrequency data, the presence of the ISW-large scale structure correlation can also be investigated through a cross-correlation of the frequency cleaned SZ and CMB maps. While convergence maps constructed from lensing surveys of the large scale structure via galaxy ellipticities are less correlated with the ISW effect, lensing potentials that deflect CMB photons are strongly correlated and allow, probably, the best mechanism to study the ISW-large scale structure correlation with CMB data alone.Comment: 10 Pages, PRD submitte
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