9,756 research outputs found
Quantum phases of mixtures of atoms and molecules on optical lattices
We investigate the phase diagram of a two-species Bose-Hubbard model
including a conversion term, by which two particles from the first species can
be converted into one particle of the second species, and vice-versa. The model
can be related to ultra-cold atom experiments in which a Feshbach resonance
produces long-lived bound states viewed as diatomic molecules. The model is
solved exactly by means of Quantum Monte Carlo simulations. We show than an
"inversion of population" occurs, depending on the parameters, where the second
species becomes more numerous than the first species. The model also exhibits
an exotic incompressible "Super-Mott" phase where the particles from both
species can flow with signs of superfluidity, but without global supercurrent.
We present two phase diagrams, one in the (chemical potential, conversion)
plane, the other in the (chemical potential, detuning) plane.Comment: 7 pages, 10 figure
Feshbach-Einstein condensates
We investigate the phase diagram of a two-species Bose-Hubbard model
describing atoms and molecules on a lattice, interacting via a Feshbach
resonance. We identify a region where the system exhibits an exotic super-Mott
phase and regions with phases characterized by atomic and/or molecular
condensates. Our approach is based on a recently developed exact quantum Monte
Carlo algorithm: the Stochastic Green Function algorithm with tunable
directionality. We confirm some of the results predicted by mean-field studies,
but we also find disagreement with these studies. In particular, we find a
phase with an atomic but no molecular condensate, which is missing in all
mean-field phase diagrams.Comment: 4 pages, 6 figure
Reduction of the COSMOS Southern Sky galaxy survey data to the RC3 standard system
After having cross-identified a subsample of LEDA galaxies in the COSMOS
database, we defined the best relations to convert COSMOS parameters
(coordinates, position angle, diameter, axis ratio and apparent magnitude) into
RC3 system used in the LEDA database. Tiny secondary effects can be tested:
distance to plate cenetrs effect and air-mass effect. The converted COSMOS
parameters are used to add missing parameters on LEDA galaxies.
Key words: galaxies - catalogue - photometryComment: 5 pages, postcript including figures, to appear in MNRAS, reprint
requests: [email protected]
Canonical Trajectories and Critical Coupling of the Bose-Hubbard Hamiltonian in a Harmonic Trap
Quantum Monte Carlo (QMC) simulations and the Local Density Approximation
(LDA) are used to map the constant particle number (canonical) trajectories of
the Bose Hubbard Hamiltonian confined in a harmonic trap onto the
phase diagram of the uniform system. Generically, these curves do not intercept
the tips of the Mott insulator (MI) lobes of the uniform system. This
observation necessitates a clarification of the appropriate comparison between
critical couplings obtained in experiments on trapped systems with those
obtained in QMC simulations. The density profiles and visibility are also
obtained along these trajectories. Density profiles from QMC in the confined
case are compared with LDA results.Comment: New version of figure 1
Superfluid and Mott Insulator phases of one-dimensional Bose-Fermi mixtures
We study the ground state phases of Bose-Fermi mixtures in one-dimensional
optical lattices with quantum Monte Carlo simulations using the Canonical Worm
algorithm. Depending on the filling of bosons and fermions, and the on-site
intra- and inter-species interaction, different kinds of incompressible and
superfluid phases appear. On the compressible side, correlations between bosons
and fermions can lead to a distinctive behavior of the bosonic superfluid
density and the fermionic stiffness, as well as of the equal-time Green
functions, which allow one to identify regions where the two species exhibit
anticorrelated flow. We present here complete phase diagrams for these systems
at different fillings and as a function of the interaction parameters.Comment: 8 pages, 12 figure
The association between parenting behavior and somatization in adolescents explained by physiological responses in adolescents
Introduction: This study adds to the knowledge on somatization in adolescents by exploring its relation with parenting behavior and the mediating/moderating role of physiological responses in adolescents to parenting behavior. Method: Eighteen adolescents with high and 18 adolescents with low somatization scores and their mothers completed a discussion task, from which observed parenting behavior scores were derived. Skin conductance in adolescents was measured before and during the discussion. Results: For adolescents with high levels of physiological responses, unadaptive parenting was related to a higher chance of high somatization scores. For low physiologically responsive adolescents, the relation between parenting behavior and somatization was not significant. Conclusion: Parenting behavior is not univocally related to somatization in adolescents, but the association depends on physiological responses in adolescents. (C) 2014 Elsevier B.V. All rights reserved
Revisiting SIFT for plant foliage in RGB images acquired on a turntable
In this work, SIFT features are revisited for their use in two applications of computer vision for plant analysis. The first application is the reconstruction of 3D models of plants through tracking homologue points in successive intensity images. The second application is to provide a new global descriptor that gives a measure of the level of self-similariy of foliage for plants of different architectures and foliar appearance. In order to properly exploit SIFT descriptors in relation to these applications, we discuss two aspects of the classical SIFT keypoint matching practice. On the one hand we propose to match detected keypoints based on a scale criterion. On the other hand, we drop the ratio rule while matching keypoints in two images and propose the use of a spatial proximity filter instead
Mott Domains of Bosons Confined on Optical Lattices
In the absence of a confining potential, the boson Hubbard model in its
ground state is known to exhibit a superfluid to Mott insulator quantum phase
transition at commensurate fillings and strong on-site repulsion. In this
paper, we use quantum Monte Carlo simulations to study the ground state of the
one dimensional bosonic Hubbard model in a trap. We show that some, but not
all, aspects of the Mott insulating phase persist when a confining potential is
present. The Mott behavior is present for a continuous range of incommensurate
fillings, a very different situation from the unconfined case. Furthermore the
establishment of the Mott phase does not proceed via a quantum phase transition
in the traditional sense. These observations have important implications for
the interpretation of experimental results for atoms trapped on optical
lattices. Initial results show that, qualitatively, the same results persist in
higher dimensions.Comment: Revtex file, five figures, include
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