8,405 research outputs found
Distributional Analyses of Revenue Options for Alaska
A new report commissioned by Rasmuson Foundation as part of its Plan4Alaska campaign finds that while strategies currently proposed to close Alaska's 100,000 (or over $200,000 for married couples)
Challenges in using science-based shoreline setbacks: Examples from South Carolina
Beachfront jurisdictional lines were established by the South Carolina Beachfront Management Act (SC Code §48-
39-250 et seq.) in 1988 to regulate the new construction, repair, or reconstruction of buildings and erosion control
structures along the state’s ocean shorelines. Building within the state’s beachfront “setback area” is allowed, but is subject to special regulations. For “standard beaches” (those not influenced by tidal inlets or associated shoals), a baseline is established at the crest of the primary oceanfront sand dune; for “unstabilized inlet zones,” the baseline is drawn at the most landward point of erosion during the past forty years. The parallel setback line is then established landward of the baseline a distance of forty times the long-term average annual erosion rate (not less than twenty feet from the baseline in stable or accreting areas). The positions of the baseline and setback line are updated every 8-10 years using the best available scientific and historical data, including aerial imagery, LiDAR, historical shorelines, beach profiles, and long-term erosion rates. One advantage of science-based setbacks is that, by using actual historical and current shoreline positions and beach profile data, they reflect the general erosion threat to
beachfront structures. However, recent experiences with revising the baseline and setback line indicate that
significant challenges and management implications also exist. (PDF contains 3 pages
SCU Courses
Registering for classes is a nightmare that students at Santa Clara University undergo three or more times a year while juggling midterm exams. It’s hard to find a schedule that works well for you, balancing the need to take classes that will satisfy degree progress with the need to work around obligations outside of class and avoid getting stuck in an 8am lecture. SCU Courses is a web app where students input their current degree progress and receive a list of possible schedules to take next quarter, collapsing the time-consuming process of carefully crafting a schedule into just one step: choose your favorite
Influence of quantum fluctuations on the superfluid critical velocity of a one-dimensional Bose gas
The mean-field Gross-Pitaevskii equation with repulsive interactions exhibits
frictionless flow when stirred by an obstacle below a critical velocity. Here
we go beyond the mean-field approximation to examine the influence of quantum
fluctuations on this threshold behaviour in a one-dimensional Bose gas in a
ring. Using the truncated Wigner approximation, we perform simulations of
ensembles of trajectories where the Bose gas is stirred with a repulsive
obstacle below the mean-field critical velocity. We observe the probabilistic
formation of grey solitons which subsequently decay, leading to an increase in
the momentum of the fluid. The formation of the first soliton leads to a
soliton cascade, such that the fluid rapidly accelerates to minimise the speed
difference with the obstacle. We measure the initial rate of momentum transfer,
and relate it to macroscopic tunnelling between quantised flow states in the
ring.Comment: 10 pages, 9 figure
The Projected Gross-Pitaevskii Equation for harmonically confined Bose gases
We extend the Projected Gross Pitaevskii equation formalism of Davis et al.
[Phys. Rev. Lett. \bf{87}, 160402 (2001)] to the experimentally relevant case
of harmonic potentials. We outline a robust and accurate numerical scheme that
can efficiently simulate this system. We apply this method to investigate the
equilibrium properties of a harmonically trapped three-dimensional Bose gas at
finite temperature, and consider the dependence of condensate fraction,
position and momentum distributions, and density fluctuations on temperature.
We apply the scheme to simulate an evaporative cooling process in which the
preferential removal of high energy particles leads to the growth of a
Bose-Einstein condensate. We show that a condensate fraction can be inferred
during the dynamics even in this non-equilibrium situation.Comment: 11 pages, 7 figure
Multimode analysis of non-classical correlations in double well Bose-Einstein condensates
The observation of non-classical correlations arising in interacting two to
size weakly coupled Bose-Einstein condensates was recently reported by Esteve
et al. [Nature 455, 1216 (2008)]. In order to observe fluctuations below the
standard quantum limit, they utilized adiabatic passage to reduce the thermal
noise to below that of thermal equilibrium at the minimum realizable
temperature. We present a theoretical analysis that takes into account the
spatial degrees of freedom of the system, allowing us to calculate the expected
correlations at finite temperature in the system, and to verify the hypothesis
of adiabatic passage by comparing the dynamics to the idealized model.Comment: 12 pages, 7 figure
Critical temperature of a trapped Bose gas: comparison of theory and experiment
We apply the Projected Gross-Pitaevskii equation (PGPE) formalism to the
experimental problem of the shift in critical temperature of a
harmonically confined Bose gas as reported in Gerbier \emph{et al.} [Phys. Rev.
Lett. \textbf{92}, 030405 (2004)]. The PGPE method includes critical
fluctuations and we find the results differ from various mean-field theories,
and are in best agreement with experimental data. To unequivocally observe
beyond mean-field effects, however, the experimental precision must either
improve by an order of magnitude, or consider more strongly interacting
systems. This is the first application of a classical field method to make
quantitative comparison with experiment.Comment: revtex4, four pages, three figures. v2: updated to published version.
Several additions to figures, and better explanations in text in response to
referee comment
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