569 research outputs found
Kinetic energy of a trapped Fermi gas interacting with a Bose-Einstein condensate
We study a confined mixture of bosons and fermions in the regime of quantal
degeneracy, with particular attention to the effects of the interactions on the
kinetic energy of the fermionic component. We are able to explore a wide region
of system parameters by identifying two scaling variables which completely
determine its state at low temperature. These are the ratio of the
boson-fermion and boson-boson interaction strengths and the ratio of the radii
of the two clouds. We find that the effect of the interactions can be sizeable
for reasonable choices of the parameters and that its experimental study can be
used to infer the sign of the boson-fermion scattering length. The interplay
between interactions and thermal effects in the fermionic kinetic energy is
also discussed.Comment: REVTEX, 8 pages, 6 figures included. Small corrections to text and
figures, accepted for publication in EPJ
Temperature-dependent density profiles of trapped boson-fermion mixtures
We present a semiclassical three-fluid model for a Bose-condensed mixture of
interacting Bose and Fermi gases confined in harmonic traps at finite
temperature. The model is used to characterize the experimentally relevant
behaviour of the equilibrium density profile of the fermions with varying
composition and temperature across the onset of degeneracy, for coupling
strengths relevant to a mixture of
K and K atoms.Comment: 9 pages, 2 postscript figures, accepted for publication in Eur. Phys.
Jour.
One-loop adjoint masses for branes at non-supersymmetric angles
This proceeding is based on arXiv:1105.0591 [hep-th] where we consider
breaking of supersymmetry in intersecting D-brane configurations by slight
deviation of the angles from their supersymmetric values. We compute the masses
generated by radiative corrections for the adjoint scalars on the brane
world-volumes. In the open string channel, the string two-point function
receives contributions only from the infrared limits of N~4 and N~2
supersymmetric configurations, via messengers and their Kaluza-Klein
excitations, and leads at leading order to tachyonic directions.Comment: 15 pages, 5 figures. Contribution to the proceedings of the Corfu
Summer Institute 2011 School and Workshops on Elementary Particle Physics and
Gravity, September 4-18 2011 Corfu, Greec
Link or sink: a modelling interpretation of the open Baltic biogeochemistry
International audienceA 1-D model system, consisting of the 1-D version of the Princeton Ocean Model (POM) coupled with the European Regional Seas Ecosystem Model (ERSEM) has been applied to a sub-basin of the Baltic Proper, the Bornholm basin. The model has been forced with 3h meteorological data for the period 1979-1990, producing a 12-year hindcast validated with datasets from the Baltic Environmental Database for the same period. The model results demonstrate the model to hindcast the time-evolution of the physical structure very well, confirming the view of the open Baltic water column as a three layer system of surface, intermediate and bottom waters. Comparative analyses of modelled hydrochemical components with respect to the independent data have shown that the long-term system behaviour of the model is within the observed ranges. Also primary production processes, deduced from oxygen (over)saturation are hindcast correctly over the entire period and the annual net primary production is within the observed range. The largest mismatch with observations is found in simulating the biogeochemistry of the Baltic intermediate waters. Modifications in the structure of the model (addition of fast-sinking detritus and polysaccharide dynamics) have shown that the nutrient dynamics are linked to the quality and dimensions of the organic matter produced in the euphotic zone, highlighting the importance of the residence time of the organic matter within the microbial foodweb in the intermediate waters. Experiments with different scenarios of riverine nutrient loads, assessed in the limits of a 1-D setup, have shown that the external input of organic matter makes the open Baltic model more heterotrophic. The characteristics of the inputs also drive the dynamics of nitrogen in the bottom layers leading either to nitrate accumulation (when the external sources are inorganic), or to coupled nitrification-denitrification (under strong organic inputs). The model indicates the permanent stratification to be the main feature of the system as regulator of carbon and nutrient budgets. The model predicts that most of the carbon produced in the euphotic zone is also consumed in the water column and this enhances the importance of heterotrophic benthic processes as final closure of carbon and nutrient cycles in the open Baltic
Factor PD-Clustering
Factorial clustering methods have been developed in recent years thanks to
the improving of computational power. These methods perform a linear
transformation of data and a clustering on transformed data optimizing a common
criterion. Factorial PD-clustering is based on Probabilistic Distance
clustering (PD-clustering). PD-clustering is an iterative, distribution free,
probabilistic, clustering method. Factor PD-clustering make a linear
transformation of original variables into a reduced number of orthogonal ones
using a common criterion with PD-Clustering. It is demonstrated that Tucker 3
decomposition allows to obtain this transformation. Factor PD-clustering makes
alternatively a Tucker 3 decomposition and a PD-clustering on transformed data
until convergence. This method could significantly improve the algorithm
performance and allows to work with large dataset, to improve the stability and
the robustness of the method
A model-based ultrametric composite indicator for studying waste management in Italian municipalities
Link or sink: a modelling interpretation of the open Baltic biogeochemistry
A 1-D model system, consisting of the 1-D version of the Princeton Ocean Model (POM) coupled with the European Regional Seas Ecosystem Model (ERSEM) has been applied to a sub-basin of the Baltic Proper, the Bornholm basin. The model has been forced with 3h meteorological data for the period 1979-1990, producing a 12-year hindcast validated with datasets from the Baltic Environmental Database for the same period. The model results demonstrate the model to hindcast the time-evolution of the physical structure very well, confirming the view of the open Baltic water column as a three layer system of surface, intermediate and bottom waters. Comparative analyses of modelled hydrochemical components with respect to the independent data have shown that the long-term system behaviour of the model is within the observed ranges. Also primary production processes, deduced from oxygen (over)saturation are hindcast correctly over the entire period and the annual net primary production is within the observed range. The largest mismatch with observations is found in simulating the biogeochemistry of the Baltic intermediate waters. Modifications in the structure of the model (addition of fast-sinking detritus and polysaccharide dynamics) have shown that the nutrient dynamics are linked to the quality and dimensions of the organic matter produced in the euphotic zone, highlighting the importance of the residence time of the organic matter within the microbial foodweb in the intermediate waters. Experiments with different scenarios of riverine nutrient loads, assessed in the limits of a 1-D setup, have shown that the external input of organic matter makes the open Baltic model more heterotrophic. The characteristics of the inputs also drive the dynamics of nitrogen in the bottom layers leading either to nitrate accumulation (when the external sources are inorganic), or to coupled nitrification-denitrification (under strong organic inputs). The model indicates the permanent stratification to be the main feature of the system as regulator of carbon and nutrient budgets. The model predicts that most of the carbon produced in the euphotic zone is also consumed in the water column and this enhances the importance of heterotrophic benthic processes as final closure of carbon and nutrient cycles in the open Baltic
Fermion conformal bootstrap in 4d
We apply numerical conformal bootstrap techniques to the four-point function
of a Weyl spinor in 4d non-supersymmetric CFTs. We find universal bounds on
operator dimensions and OPE coefficients, including bounds on operators in
mixed symmetry representations of the Lorentz group, which were inaccessible in
previous bootstrap studies. We find discontinuities in some of the bounds on
operator dimensions, and we show that they arise due to a generic yet
previously unobserved fake primary effect, which is related to the existence of
poles in conformal blocks. We show that this effect is also responsible for
similar discontinuities found in four-fermion bootstrap in 3d, as well as in
the mixed-correlator analysis of the 3d Ising CFT. As an important byproduct of
our work, we develop a practical technology for numerical approximation of
general 4d conformal blocks
Strengthening of the hydrological cycle in future scenarios: atmospheric energy and water balance perspective
Abstract. Future climate scenarios experiencing global warming are expected to strengthen the hydrological cycle during the 21st century (21C). We analyze the strengthening of the global-scale increase in precipitation from the perspective of changes in whole atmospheric water and energy balances. By combining energy and water equations for the whole atmosphere, we obtain constraints for the changes in surface fluxes and partitioning at the surface between sensible and latent components. We investigate the differences in the strengthening of the hydrological cycle in two centennial simulations performed with an Earth system model forced with specified atmospheric concentration pathways. Alongside the Special Report on Emissions Scenario (SRES) A1B, which is a medium-high non-mitigation scenario, we consider a new aggressive-mitigation scenario (E1) with reduced fossil fuel use for energy production aimed at stabilizing global warming below 2 K. Our results show that the mitigation scenario effectively constrains the global warming with a stabilization below 2 K with respect to the 1950–2000 historical period. On the other hand, the E1 precipitation does not follow the temperature field toward a stabilization path but continues to increase over the mitigation period. Quite unexpectedly, the mitigation scenario is shown to strengthen the hydrological cycle even more than SRES A1B till around 2070. We show that this is mostly a consequence of the larger increase in the negative radiative imbalance of atmosphere in E1 compared to A1B. This appears to be primarily related to decreased sulfate aerosol concentration in E1, which considerably reduces atmospheric absorption of solar radiation compared to A1B. The last decades of the 21C show a marked increase in global precipitation in A1B compared to E1, despite the fact that the two scenarios display almost the same overall increase of radiative imbalance with respect to the 20th century. Our results show that radiative cooling is weakly effective in A1B throughout the 21C. Two distinct mechanisms characterize the diverse strengthening of the hydrological cycle in the middle and end- 21C. It is only through a very large perturbation of surface fluxes that A1B achieves a larger increase in global precipitation in the last decades of the 21C. Our energy/water budget analysis shows that this behavior is ultimately due to a bifurcation in the Bowen ratio change between the two scenarios. This work warns that mitigation policies that promote aerosol abatement, may lead to an unexpected stronger intensification of the hydrological cycle and associated changes that may last for decades after global warming is effectively mitigated. On the other hand, it is also suggested that predictable components of the radiative forcing by aerosols may have the potential to effectively contribute to the decadal-scale predictability of changes in the hydrological strength
Breathing Oscillations in Bose - Fermi Mixing Gases with Yb atoms in the Largely Prolate Deformed Traps
We study the breathing oscillations in bose-fermi mixtures with Yb isotopes
in the largely prolate deformed trap, which are realized by Kyoto group. We
choose the three combinations of the Yb isotopes, Yb170-Yb171, Yb170-Yb173 and
Yb174-Yb173, whose boson-fermion interactions are weakly repulsive, strongly
attractive and strongly repulsive. The collective oscillations in the deformed
trap are calculated in the dynamical time-development approach, which is
formulated with the time-dependent Gross-Pitaevskii and the Vlasov equations.
We analyze the results in the time-development approach with the intrinsic
oscillation modes of the deformed system, which are obtained using the scaling
method, and show that the damping and forced-oscillation effects of the
intrinsic modes give time-variation of oscillations, especially, in the fermion
transverse mode.Comment: 27 pages, 12 figure
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