1,037 research outputs found

    The Role of Scientific Evidence in Canada\u27s West Coast Energy Conflicts

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    With salience, credibility, and legitimacy as organizing themes, we investigated how opposing communities engaged with scientific information for two contentious proposed energy projects in western Canada, and how their perceptions of science influenced its use in decision-making. The Trans Mountain pipeline expansion, to carry diluted bitumen from northern Alberta’s oil sands to tankers on British Columbia’s (BC) south coast, was expected to adversely impact biodiversity and contribute to climate change. The Bute Inlet hydroelectric project, a large renewable energy project planned for BC’s Central Coast, was anticipated to impact biodiversity but was largely seen as climate-friendly. Based on surveys and interviews with 68 participants who had made one or more personal or professional decisions pertaining to the projects, we discovered that values, cultural cognition, and media effects permeated all aspects of using scientific evidence—from commissioning scientific research to selecting, assessing, and weighing it with other forms of information. As a result, science was developed and used to support positions rather than to inform decisions. We discuss ways to improve the use of science in environmental assessments and other planning and development processes where engaged communities are divided by oppositional positions. We hope this research will lead to community-university partnerships that identify broadly salient, credible, and legitimate sources of information about energy and climate issues, and foster knowledge mobilization across conflict divides

    Isotope shift calculations for atoms with one valence electron

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    This work presents a method for the ab initio calculation of isotope shift in atoms and ions with one valence electron above closed shells. As a zero approximation we use relativistic Hartree-Fock and then calculate correlation corrections. The main motivation for developing the method comes from the need to analyse whether different isotope abundances in early universe can contribute to the observed anomalies in quasar absorption spectra. The current best explanation for these anomalies is the assumption that the fine structure constant, alpha, was smaller at early epoch. We test the isotope shift method by comparing the calculated and experimental isotope shift for the alkali and alkali-like atoms Na, MgII, K, CaII and BaII. The agreement is found to be good. We then calculate the isotope shift for some astronomically relevant transitions in SiII and SiIV, MgII, ZnII and GeII.Comment: 11 page

    The integral monodromy of hyperelliptic and trielliptic curves

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    We compute the \integ/\ell and \integ_\ell monodromy of every irreducible component of the moduli spaces of hyperelliptic and trielliptic curves. In particular, we provide a proof that the \integ/\ell monodromy of the moduli space of hyperelliptic curves of genus gg is the symplectic group \sp_{2g}(\integ/\ell). We prove that the \integ/\ell monodromy of the moduli space of trielliptic curves with signature (r,s)(r,s) is the special unitary group \su_{(r,s)}(\integ/\ell\tensor\integ[\zeta_3])

    Non-linear regression models for Approximate Bayesian Computation

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    Approximate Bayesian inference on the basis of summary statistics is well-suited to complex problems for which the likelihood is either mathematically or computationally intractable. However the methods that use rejection suffer from the curse of dimensionality when the number of summary statistics is increased. Here we propose a machine-learning approach to the estimation of the posterior density by introducing two innovations. The new method fits a nonlinear conditional heteroscedastic regression of the parameter on the summary statistics, and then adaptively improves estimation using importance sampling. The new algorithm is compared to the state-of-the-art approximate Bayesian methods, and achieves considerable reduction of the computational burden in two examples of inference in statistical genetics and in a queueing model.Comment: 4 figures; version 3 minor changes; to appear in Statistics and Computin

    Constraining fundamental constants of physics with quasar absorption line systems

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    We summarize the attempts by our group and others to derive constraints on variations of fundamental constants over cosmic time using quasar absorption lines. Most upper limits reside in the range 0.5-1.5x10-5 at the 3sigma level over a redshift range of approximately 0.5-2.5 for the fine-structure constant, alpha, the proton-to-electron mass ratio, mu, and a combination of the proton gyromagnetic factor and the two previous constants, gp(alpha^2/mu)^nu, for only one claimed variation of alpha. It is therefore very important to perform new measurements to improve the sensitivity of the numerous methods to at least <0.1x10-5 which should be possible in the next few years. Future instrumentations on ELTs in the optical and/or ALMA, EVLA and SKA pathfinders in the radio will undoutedly boost this field by allowing to reach much better signal-to-noise ratios at higher spectral resolution and to perform measurements on molecules in the ISM of high redshift galaxies.Comment: 11 pages, 3 figure

    Search for varying constants of nature from astronomical observation of molecules

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    The status of searches for possible variation in the constants of nature from astronomical observation of molecules is reviewed, focusing on the dimensionless constant representing the proton-electron mass ratio μ=mp/me\mu=m_p/m_e. The optical detection of H2_2 and CO molecules with large ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as the detection of H2_2 with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope is discussed in the context of varying constants, and in connection to different theoretical scenarios. Radio astronomy provides an alternative search strategy bearing the advantage that molecules as NH3_3 (ammonia) and CH3_3OH (methanol) can be used, which are much more sensitive to a varying μ\mu than diatomic molecules. Current constraints are ∣Δμ/μ∣<5×10−6|\Delta\mu/\mu| < 5 \times 10^{-6} for redshift z=2.0−4.2z=2.0-4.2, corresponding to look-back times of 10-12.5 Gyrs, and ∣Δμ/μ∣<1.5×10−7|\Delta\mu/\mu| < 1.5 \times 10^{-7} for z=0.88z=0.88, corresponding to half the age of the Universe (both at 3σ\sigma statistical significance). Existing bottlenecks and prospects for future improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the International Space Science Institute, Bern 201

    Lepton flavour violating Higgs Boson decays, tau --> mu gamma and B(s) --> mu+mu- in the constrained MSSM+NR with large tan beta

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    Realistic predictions are made for the rates of lepton flavour violating Higgs boson decays, tau --> mu gamma, mu --> e gamma, Bs --> mu+mu-, Bs --> tau mu and tau --> 3mu, via a top-down analysis of the Minimal Supersymmetric Standard Model(MSSM) constrained by SU(5) unification with right-handed Neutrinos and large tan beta. The third family neutrino Yukawa coupling is chosen to be of order 1, in this way our model bares a significant resemblance to supersymmetric SO(10). In this framework the large PMNS mixings result in potentially large lepton flavour violation. Our analysis predicts tau --> mu gamma and mu --> e gamma rates in the region (10^{-8}-10^{-6}) and (10^{-15}-10^{-14}) respectively. We also show that the rates for lepton flavour violating Higgs decays can be as large as 10^{-7}. The non-decoupling nature of H --> tau mu is observed which leads to its decay rate becoming comparable to that for tau --> mu gamma for large values of m_0 and M_1/2. We also find that the present bound on Bs --> mu+mu- is an important constraint on the rate of lepton flavour violating Higgs decays. The recently measured Bs-Bsbar mixing parameter Delta Ms is also investigated.Comment: 27 pages, 15 postscript figures, 1 table. Small changes made to the text and title. Updated references. Bs-Bsbar analysis also include

    Feedback-control of quantum systems using continuous state-estimation

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    We present a formulation of feedback in quantum systems in which the best estimates of the dynamical variables are obtained continuously from the measurement record, and fed back to control the system. We apply this method to the problem of cooling and confining a single quantum degree of freedom, and compare it to current schemes in which the measurement signal is fed back directly in the manner usually considered in existing treatments of quantum feedback. Direct feedback may be combined with feedback by estimation, and the resulting combination, performed on a linear system, is closely analogous to classical LQG control theory with residual feedback.Comment: 12 pages, multicol revtex, revised and extende

    Thermal leptogenesis in a model with mass varying neutrinos

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    In this paper we consider the possibility of neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling between the right-handed neutrinos and the dark energy scalar field, the Quintessence. In our model, the right-handed neutrino masses change as the Quintessence scalar evolves. We then examine in detail the parameter space of this model allowed by the observed baryon number asymmetry. Our results show that it is possible to lower the reheating temperature in this scenario in comparison with the case that the neutrino masses are unchanged, which helps solve the gravitino problem. Furthermore, a degenerate neutrino mass patten with mim_i larger than the upper limit given in the minimal leptogenesis scenario is permitted.Comment: 18 pages, 7 figures, version to appear in PR
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