1,037 research outputs found
The Role of Scientific Evidence in Canada\u27s West Coast Energy Conflicts
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
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
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 is the symplectic group
\sp_{2g}(\integ/\ell). We prove that the \integ/\ell monodromy of the
moduli space of trielliptic curves with signature is the special
unitary group \su_{(r,s)}(\integ/\ell\tensor\integ[\zeta_3])
Non-linear regression models for Approximate Bayesian Computation
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
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
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
. The optical detection of H and CO molecules with large
ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as
the detection of H 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 NH
(ammonia) and CHOH (methanol) can be used, which are much more sensitive to
a varying than diatomic molecules. Current constraints are
for redshift , corresponding to
look-back times of 10-12.5 Gyrs, and for
, corresponding to half the age of the Universe (both at 3
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
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
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
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 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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