6,317 research outputs found
Spin-3 Chromium Bose-Einstein Condensates
We analyze the physics of spin-3 Bose-Einstein condensates, and in particular
the new physics expected in on-going experiments with condensates of Chromium
atoms. We first discuss the ground-state properties, which, depending on still
unknown Chromium parameters, and for low magnetic fields can present various
types of phases. We also discuss the spinor-dynamics in Chromium spinor
condensates, which present significant qualitative differences when compared to
other spinor condensates. In particular, dipole-induced spin relaxation may
lead for low magnetic fields to transfer of spin into angular momentum similar
to the well-known Einstein-de Haas effect. Additionally, a rapid large
transference of population between distant magnetic states becomes also
possible.Comment: 4 pages, 3 eps figures. Error in the previous version correcte
Dynamical mean-field equations for strongly interacting fermionic atoms in a potential trap
We derive a set of dynamical mean-field equations for strongly interacting
fermionic atoms in a potential trap across a Feshbach resonance. Our derivation
is based on a variational ansatz, which generalizes the crossover wavefunction
to the inhomogeneous case, and the assumption that the order parameter is
slowly varying over the size of the Cooper pairs. The equations reduce to a
generalized time-dependent Gross-Pitaevskii equation on the BEC side of the
resonance. We discuss an iterative method to solve these mean-field equations,
and present the solution for a harmonic trap as an illustrating example to
self-consistently verify the approximations made in our derivation.Comment: replaced with the published versio
LHC and dark matter signals of Z' bosons
We customize the simulation code FEWZ (Fully Exclusive W, Z Production) to
study Z' production at the LHC for both \sqrt{s}=8 TeV and 14 TeV. Using the
results of our simulation for several standard benchmark Z' models, we derive a
semi-empirical expression for the differential cross section, that permits the
determination of Z' couplings in a model-independent manner. We evaluate cross
sections and other observables for large classes of models, including the
common E_6, left-right and B-L models, as a function of model parameters. We
also consider a hidden sector Z' that couples to standard model fermions via
kinetic and mass mixing and serves as a mediator of isospin-violating
interactions with dark matter. We combine the results of LHC Z' searches and
dark matter direct detection experiments with global electroweak data to obtain
mass-dependent constraints on the model parameters.Comment: 30 pages, 19 figures, 2 tables. Published versio
Sensing Subjective Well-being from Social Media
Subjective Well-being(SWB), which refers to how people experience the quality
of their lives, is of great use to public policy-makers as well as economic,
sociological research, etc. Traditionally, the measurement of SWB relies on
time-consuming and costly self-report questionnaires. Nowadays, people are
motivated to share their experiences and feelings on social media, so we
propose to sense SWB from the vast user generated data on social media. By
utilizing 1785 users' social media data with SWB labels, we train machine
learning models that are able to "sense" individual SWB from users' social
media. Our model, which attains the state-by-art prediction accuracy, can then
be used to identify SWB of large population of social media users in time with
very low cost.Comment: 12 pages, 1 figures, 2 tables, 10th International Conference, AMT
2014, Warsaw, Poland, August 11-14, 2014. Proceeding
Willingness-to-Pay for Improved Air Quality in Hamilton-Wentworth: A Choice Experiment
Prepared for Hamilton-Wentworth Air Quality Initiative pursuant to a memorandum of understanding among McMaster University, the Ontario Ministry of Environment and Energy and the Regional Municipality of Hamilton-Wentworth, dated November 5, 1996.
Review of Territory: On the Development of Landscape and City by ETH Studio Basel: Contemporary City Institute. With contributions by Roger Diener, Liisa Gunnarsson, Mathias Gunz, Vesna Jovanović, Marcel Meili, Christan Müller Inderbitzin, and Christian Schmid
Book review of Territory: On the Development of Landscape and City by ETH Studio Basel: Contemporary City Institute
Ramping fermions in optical lattices across a Feshbach resonance
We study the properties of ultracold Fermi gases in a three-dimensional
optical lattice when crossing a Feshbach resonance. By using a zero-temperature
formalism, we show that three-body processes are enhanced in a lattice system
in comparison to the continuum case. This poses one possible explanation for
the short molecule lifetimes found when decreasing the magnetic field across a
Feshbach resonance. Effects of finite temperatures on the molecule formation
rates are also discussed by computing the fraction of double-occupied sites.
Our results show that current experiments are performed at temperatures
considerably higher than expected: lower temperatures are required for
fermionic systems to be used to simulate quantum Hamiltonians. In addition, by
relating the double occupancy of the lattice to the temperature, we provide a
means for thermometry in fermionic lattice systems, previously not accessible
experimentally. The effects of ramping a filled lowest band across a Feshbach
resonance when increasing the magnetic field are also discussed: fermions are
lifted into higher bands due to entanglement of Bloch states, in good agreement
with recent experiments.Comment: 9 pages, 7 figure
Integrated optics prototype beam combiner for long baseline interferometry in the L and M bands
In the last few years, integrated optics (IO) beam combiners have facilitated
the emergence of 4-telescope interferometers such as PIONIER or GRAVITY,
boosting the imaging capabilities of the VLTI. However, the spectral range
beyond 2.2microns is not ideally covered by the conventional silica based IO.
Here, we propose to consider new laser-written IO prototypes made of GLS
glasses, a material that permits access to the mid-infrared spectral regime.
Our goal is to conduct a full characterization of our mid-IR IO 2-telescope
coupler in order to measure the performance levels directly relevant for
long-baseline interferometry. We focus in particular on the exploitation of the
L and M astronomical bands. We use a dedicated Michelson-interferometer setup
to perform Fourier Transform spectroscopy on the coupler and measure its
broadband interferometric performance. We also analyze the polarization
properties of the coupler, the differential dispersion and phase degradation as
well as the modal behavior and the total throughput. We measure broadband
interferometric contrasts of 94.9% and 92.1% for unpolarized light in the L and
M bands. Spectrally integrated splitting ratios are close to 50% but show
chromatic dependence over the considered bandwidths. Additionally, the phase
variation due to the combiner is measured and does not exceed 0.04rad and
0.07rad across the band L and M band, respectively. The total throughput of the
coupler including Fresnel and injection losses from free-space is 25.4%. The
laser-written IO GLS prototype combiners prove to be a reliable technological
solution with promising performance for mid-infrared long-baseline
interferometry. In the next steps, we will consider more advanced optical
functions as well as a fiber-fed input and revise the optical design parameters
in order the further enhance the total throughput and achromatic behavior
Accurate Evolutions of Orbiting Binary Black Holes
We present a detailed analysis of binary black hole evolutions in the last orbit and demonstrate consistent and convergent results for the trajectories of the individual bodies. The gauge choice can significantly affect the overall accuracy of the evolution. It is possible to reconcile certain gauge-dependent discrepancies by examining the convergence limit. We illustrate these results using an initial data set recently evolved by Brügmann et al. [Phys. Rev. Lett. 92, 211101 (2004)]. For our highest resolution and most accurate gauge, we estimate the duration of this data set's last orbit to be approximately 59MADM
Happiness and the Human Development Index : the paradox of Australia
According to the well-being measure known as the U.N. Human
Development Index, Australia now ranks 3rd in the world and higher than all other English-speaking nations. This paper questions that assessment. It reviews work on the economics of happiness, considers implications for policymakers, and explores where Australia lies in international subjective
well-being rankings. Using new data on approximately 50,000 randomly sampled individuals from 35 nations, the paper shows that Australians have some of the lowest levels of job satisfaction in the world. Moreover, among the sub-sample of English-speaking nations, where a common language
should help subjective measures to be reliable, Australia performs poorly on a range of happiness indicators. The paper discusses this paradox. Our purpose is not to reject HDI methods, but rather to argue that much remains
to be understood in this area
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