4,650 research outputs found
Effective theory of excitations in a Feshbach resonant superfluid
A strongly interacting Fermi gas, such as that of cold atoms operative near a
Feshbach resonance, is difficult to study by perturbative many-body theory to
go beyond mean field approximation. Here I develop an effective field theory
for the resonant superfluid based on broken symmetry. The theory retains both
fermionic quasiparticles and superfluid phonons, the interaction between them
being derived non-perturbatively. The theory converges and can be improved
order by order, in a manner governed by a low energy expansion rather than by
coupling constant. I apply the effective theory to calculate the specific heat
and propose a mechanism of understanding the empirical power law of energy
versus temperature recently measured in a heat capacity experiment.Comment: 4+ pages, 1 figure; Added references, corrected and clarified minor
statements (v.2
Incommensurate superfluidity of bosons in a double-well optical lattice
We study bosons in the first excited Bloch band of a double-well optical
lattice, recently realized at NIST. By calculating the relevant parameters from
a realistic nonseparable lattice potential, we find that in the most favorable
cases the boson lifetime in the first excited band can be several orders of
magnitude longer than the typical nearest-neighbor tunnelling timescales, in
contrast to that of a simple single-well lattice. In addition, for sufficiently
small lattice depths the excited band has minima at nonzero momenta
incommensurate with the lattice period, which opens a possibility to realize an
exotic superfluid state that spontaneously breaks the time-reversal,
rotational, and translational symmetries. We discuss possible experimental
signatures of this novel state.Comment: 4 pages, 5 figures
Implicit 3D Orientation Learning for 6D Object Detection from RGB Images
We propose a real-time RGB-based pipeline for object detection and 6D pose
estimation. Our novel 3D orientation estimation is based on a variant of the
Denoising Autoencoder that is trained on simulated views of a 3D model using
Domain Randomization. This so-called Augmented Autoencoder has several
advantages over existing methods: It does not require real, pose-annotated
training data, generalizes to various test sensors and inherently handles
object and view symmetries. Instead of learning an explicit mapping from input
images to object poses, it provides an implicit representation of object
orientations defined by samples in a latent space. Our pipeline achieves
state-of-the-art performance on the T-LESS dataset both in the RGB and RGB-D
domain. We also evaluate on the LineMOD dataset where we can compete with other
synthetically trained approaches. We further increase performance by correcting
3D orientation estimates to account for perspective errors when the object
deviates from the image center and show extended results.Comment: Code available at: https://github.com/DLR-RM/AugmentedAutoencode
Breached pairing superfluidity: Possible realization in QCD
We propose a wide universality class of gapless superfluids, and analyze a
limit that might be realized in quark matter at intermediate densities. In the
breached pairing color superconducting phase heavy -quarks, with a small
Fermi surface, pair with light or quarks. The groundstate has a
superfluid and a normal Fermi component simultaneously. We expect a second
order phase transition, as a function of increasing density, from the breached
pairing phase to the conventional color-flavor locked (CFL) phase.Comment: 5 pages, latex, 1 figure; added references; Comment on Ref. [10]
change
A Proposed Model for the Investigation of Imitation Behavior on ERP Adoption
In the proposed project, we will investigate the imitation effect on technology adoption using Enterprise Resource Planning (ERP) systems as an example. This approach will offer a completely new perspective on IT adoption as a less rational behavior, even for critical ERP investment at the organizational level. Along with this investigation of the imitation-adoption relationship, our research will evaluate the moderating effect of experience on imitation behavior. We believe that imitation behavior will be strongest when an organization is considering ERP for initial adoption. However, when an organization has accumulated „experience‟ of ERP over time, its adoption of subsequent ERP modules will probably follow a more rational decision process, as explained by traditional adoption theories
Examining ERP Committee Beliefs: A Comparison of Alternative Models
Various models have been proposed to explain information technology (IT) adoption behavior. However, these models are based primarily on logical deliberation. In reality, it is impossible to obtain perfect information for a rational evaluation of new or emerging IT. In this situation, sometimes the “best alternative” is imitation. We believe that two opposing forces influence the beliefs of enterprise resource planning (ERP) committee members: rational and imitative. We propose here an integrated model and examine it together with diffusion of innovation (DOI) and imitation models. The study findings indicate that our integrated model has better explanatory power. In addition, imitative forces are shown to have a consistent direct effect and significant indirect effect on beliefs. Hence, imitative forces play a crucial role in the decision-making process, which opens up a new avenue for research into technology adoption
Interior Gap Superfluidity
We propose a new state of matter in which the pairing interactions carve out
a gap within the interior of a large Fermi ball, while the exterior surface
remains gapless. This defines a system which contains both a superfluid and a
normal Fermi liquid simultaneously, with both gapped and gapless quasiparticle
excitations. This state can be realized at weak coupling. We predict that a
cold mixture of two species of fermionic atoms with different mass will exhibit
this state. For electrons in appropriate solids, it would define a material
that is simultaneously superconducting and metallic.Comment: 5 page
Designing and Optimizing a Healthcare Kiosk for the Community
Investigating new ways to deliver care, such as the use of self-service kiosks to collect and monitor signs of wellness, supports healthcare efficiency and inclusivity. Self-service kiosks offer this potential, but there is a need for solutions to meet acceptable standards, e.g., provision of accurate measurements. This study investigates the design and optimization of a prototype healthcare kiosk to collect vital signs measures. The design problem was decomposed, formalized, focused and used to generate multiple solutions. Systematic implementation and evaluation allowed for the optimization of measurement accuracy, first for individuals and then for a population. The optimized solution was tested independently to check the suitability of the methods, and quality of the solution. The process resulted in a reduction of measurement noise and an optimal fit, in terms of the positioning of measurement devices. This guaranteed the accuracy of the solution and provides a general methodology for similar design problems
Different Methods for the Two-Nucleon T-Matrix in the Operator Form
We compare three methods to calculate the nucleon-nucleon t-matrix based on
the three-dimensional formulation of J. Golak et al., Phys. Rev. C 81, 034006,
(2010). In the first place we solve a system of complex linear inhomogeneous
equations directly for the t-matrix. Our second method is based on iterations
and a variant of the Lanczos algorithm. In the third case we obtain the
t-matrix in two steps, solving a system of real linear equations for the
k-matrix expansion coefficients and then solving an on-shell equation, which
connects the scalar coefficients of the k- and t-matrices. A very good
agreement among the three methods is demonstrated for selected nucleon-nucleon
scattering observables using a chiral next-to-next-to-leading-order
neutron-proton potential. We also apply our three-dimensional framework to the
demanding problem of proton-proton scattering, using a corresponding version of
the nucleon-nucleon potential and supplementing it with the (screened) Coulomb
force, taken also in the three-dimensional form. We show converged results for
two different screening functions and find a very good agreement with other
methods dealing with proton-proton scattering.Comment: 18 pages, 10 figures (54 eps files
Bayesian Joint Detection-Estimation of cerebral vasoreactivity from ASL fMRI data
International audienceAlthough the study of cerebral vasoreactivity using fMRI is mainly conducted through the BOLD fMRI modality, owing to its relatively high signal-to-noise ratio (SNR), ASL fMRI provides a more interpretable measure of cerebral vasoreactivity than BOLD fMRI. Still, ASL suffers from a low SNR and is hampered by a large amount of physiological noise. The current contribution aims at improving the re- covery of the vasoreactive component from the ASL signal. To this end, a Bayesian hierarchical model is proposed, enabling the recovery of per- fusion levels as well as fitting their dynamics. On a single-subject ASL real data set involving perfusion changes induced by hypercapnia, the approach is compared with a classical GLM-based analysis. A better goodness-of-fit is achieved, especially in the transitions between baseline and hypercapnia periods. Also, perfusion levels are recovered with higher sensitivity and show a better contrast between gray- and white matter
- …