2,021 research outputs found
SU(N) Fermions in a One-Dimensional Harmonic Trap
We conduct a theoretical study of SU(N) fermions confined by a
one-dimensional harmonic potential. Firstly, we introduce a new numerical
approach for solving the trapped interacting few-body problem, by which one may
obtain accurate energy spectra across the full range of interaction strengths.
In the strong-coupling limit, we map the SU(N) Hamiltonian to a spin-chain
model. We then show that an existing, extremely accurate ansatz - derived for a
Heisenberg SU(2) spin chain - is extendable to these N-component systems.
Lastly, we consider balanced SU(N) Fermi gases that have an equal number of
particles in each spin state for N=2, 3, 4. In the weak- and strong-coupling
regimes, we find that the ground-state energies rapidly converge to their
expected values in the thermodynamic limit with increasing atom number. This
suggests that the many-body energetics of N-component fermions may be
accurately inferred from the corresponding few-body systems of N
distinguishable particles.Comment: 15 pages, 6 figure
Shuttle-launch triangular space station
A triangular space station deployable in orbit is described. The framework is comprized of three trusses, formed of a pair of generally planar faces consistine of foldable struts. The struts expand and lock into rigid structural engagement forming a repetition of equilater triangles and nonfolding diagonal struts interconnecting the two faces. The struts are joined together by node fittings. The framework can be packaged into a size and configuration transportable by a space shuttle. When deployed, the framework provides a large work/construction area and ample planar surface area for solar panels and thermal radiators. A plurity of modules are secured to the framework and then joined by tunnels to make an interconnected modular display. Thruster units for the space station orientation and altitude maintenance are provided
Frustrated orbital Feshbach resonances in a Fermi gas
The orbital Feshbach resonance (OFR) is a novel scheme for magnetically
tuning the interactions in closed-shell fermionic atoms. Remarkably, unlike the
Feshbach resonances in alkali atoms, the open and closed channels of the OFR
are only very weakly detuned in energy. This leads to a unique effect whereby a
medium in the closed channel can Pauli block, or frustrate, the two-body
scattering processes. Here, we theoretically investigate the impact of
frustration in the few- and many-body limits of the experimentally accessible
three-dimensional Yb system. We find that by adding a closed-channel
atom to the two-body problem, the binding energy of the ground state is
significantly suppressed, and by introducing a closed-channel Fermi sea to the
many-body problem, we can drive the system towards weaker fermion pairing.
These results are potentially relevant to superconductivity in solid-state
multiband materials, as well as to the current and continuing exploration of
unconventional Fermi-gas superfluids near the OFR.Comment: 14 pages, 6 figure
Metacarpophalangeal pattern profile analysis of a sample drawn from a North Wales population
This is tha author's PDF version of an article published in Annals of human biology© 2001. The definitive version is available at http://www.tandf.co.uk/journalsSexual dimorphism and population differences were investigated using metacarpophalangeal pattern profile (MCPP) analysis. Although it is an anthropmetric technique, MCPP analysis is more frequently used in genetic syndrome analysis and has been under-used in the study of human groups. The present analysis used a series of hand radiographics from Gwynedd, North Wales, to make comparisons, first, between the sexes within the sample and then with previously reported data from Japan. The Welsh sexes showed MCPP analyses that indicated size and shape differences but certain similarities in shape were also evident. Differences with the Japanese data were more marked. MCPP anlysis is a potentially useful anthropmetric technique but requires further statistical development
Asymmetric Fermi superfluid with different atomic species in a harmonic trap
We study the dilute fermion gas with pairing between two species and unequal
concentrations in a harmonic trap using the mean field theory and the local
density approximation. We found that the system can exhibit a superfluid shell
structure sandwiched by the normal fermions. This superfluid shell structure
occurs if the mass ratio is larger then certain critical value which increases
from the weak-coupling BCS region to the strong-coupling BEC side. In the
strong coupling BEC regime, the radii of superfluid phase are less sensitive to
the mass ratios and are similar to the case of pairing with equal masses.
However, the lighter leftover fermions are easier to mix with the superfluid
core than the heavier ones. A partially polarized superfluid can be found if
the majority fermions are lighter, whereas phase separation is still found if
they are heavier.Comment: 12 pages, 7 figure
My mind is made up: Cancer concern and women’s preferences for contralateral prophylactic mastectomy
© 2019 John Wiley & Sons Ltd The fear of cancer recurrence is cited as a motivator of women's preferences between routine monitoring and contralateral prophylactic mastectomy (CPM) as methods of managing ongoing breast cancer risk. We conducted a discrete choice experiment among a general community sample of women who completed 12 hypothetical choices between routine monitoring and CPM described by aspects of treatment efficacy, safety, cost and involvement in decision-making. Respondents also completed a modified cancer worry question to assess cancer concern. Approximately 57.5% of 464 women always chose one option, typically routine monitoring. The majority (71.5%) reported being concerned about cancer recurrence when completing choice tasks. Latent class analysis identified three groups: preferred routine monitoring; preferred CPM; and “traders” (willing to swap between options). Among traders, women were less likely to choose an option associated with higher risk of recurrence. Women were more likely to choose options associated with less-intrusive monitoring methods and where they were involved in decision-making. Women concerned about cancer recurrence were more likely to choose CPM over monitoring. This study shows that women's preferences about how to manage breast cancer recurrence risk reflect the importance of the associated health effects, experience of care and attitudes to cancer recurrence
Artificial Intelligence in Various Sectors
The junction of AI and computer security is an area of increasing concern, due to the imminent application of AI to fielded systems. Two new areas of research need are identified: artificial intelligence techniques in the development of secure systems. An artificial intelligence system developed for a commercial bank to increase the productivity and effectiveness of funds transfer telex request operations. These telexes were previously processed manually. The advancement in computer technology has encouraged the researchers to develop software for assisting doctors in making decision without consulting the specialists directly
Superfluid phase transition and strong-coupling effects in an ultracold Fermi gas with mass imbalance
We investigate the superfluid phase transition and effects of mass imbalance
in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation)
crossover regime of an cold Fermi gas. We point out that the Gaussian
fluctuation theory developed by Nozi\`eres and Schmitt-Rink and the -matrix
theory, that are now widely used to study strong-coupling physics of cold Fermi
gases, give unphysical results in the presence of mass imbalance. To overcome
this problem, we extend the -matrix theory to include higher-order pairing
fluctuations. Using this, we examine how the mass imbalance affects the
superfluid phase transition. Since the mass imbalance is an important key in
various Fermi superfluids, such as K-Li Fermi gas mixture, exciton
condensate, and color superconductivity in a dense quark matter, our results
would be useful for the study of these recently developing superfluid systems.Comment: 7 pages, 4 figures, Proceedings of QFS-201
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