28 research outputs found
Three-body recombination rates near a Feshbach resonance within a two-channel contact interaction model
We calculate the three-body recombination rate into a shallow dimer in a gas
of cold bosonic atoms near a Feshbach resonance using a two-channel contact
interaction model. The two-channel model naturally describes the variation of
the scattering length through the Feshbach resonance and has a finite effective
range. We confront the theory with the available experimental data and show
that the two-channel model is able to quantitatively describe the existing
data. The finite effective range leads to a reduction of the scaling factor
between the recombination minima from the universal value of 22.7. The
reduction is larger for larger effective ranges or, correspondingly, for
narrower Feshbach resonances.Comment: 9 pages, 7 figure
NeutronC scattering near an Efimov state
The low-energy neutronC scattering in a neutron-neutron-core model is
studied with large scattering lengths near the conditions for the appearance of
an Efimov state. We show that the real part of the elastic wave phase-shift
() presents a zero, or a pole in , when the
system has an Efimov excited or virtual state. More precisely the pole scales
with the energy of the Efimov state (bound or virtual). We perform calculations
in the limit of large scattering lengths, disregarding the interaction range,
within a renormalized zero-range approach using subtracted equations. It is
also presented a brief discussion of these findings in the context of ultracold
atom physics with tunable scattering lengths
Observation of an Efimov spectrum in an atomic system
In 1970 V. Efimov predicted a puzzling quantum-mechanical effect that is
still of great interest today. He found that three particles subjected to a
resonant pairwise interaction can join into an infinite number of loosely bound
states even though each particle pair cannot bind. Interestingly, the
properties of these aggregates, such as the peculiar geometric scaling of their
energy spectrum, are universal, i.e. independent of the microscopic details of
their components. Despite an extensive search in many different physical
systems, including atoms, molecules and nuclei, the characteristic spectrum of
Efimov trimer states still eludes observation. Here we report on the discovery
of two bound trimer states of potassium atoms very close to the Efimov
scenario, which we reveal by studying three-particle collisions in an ultracold
gas. Our observation provides the first evidence of an Efimov spectrum and
allows a direct test of its scaling behaviour, shedding new light onto the
physics of few-body systems.Comment: 10 pages, 3 figures, 1 tabl
Critical report of current fisheries management measures implemented for the North Sea mixed demersal fisheries
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
Householders’ Mental Models of Domestic Energy Consumption: Using a Sort-And-Cluster Method to Identify Shared Concepts of Appliance Similarity
If in-home displays and other interventions are to successfully influence people's energy consumption, they need to communicate about energy in terms that make sense to users. Here we explore householders' perceptions of energy consumption, using a novel combination of card-sorting and clustering to reveal shared patterns in the way people think about domestic energy consumption. The data suggest that, when participants were asked to group appliances which they felt naturally 'went together', there are relatively few shared ideas about which appliances are conceptually related. To the extent participants agreed on which appliances belonged together, these groupings were based on activities (e.g., entertainment) and location within the home (e.g., kitchen); energy consumption was not an important factor in people's categorisations. This suggests messages about behaviour change aimed at reducing energy consumption might better be tied to social practices than to consumption itself