Ground-state properties of trapped Bose-Fermi mixtures: role of exchange-correlation

We introduce Density Functional Theory for inhomogeneous Bose-Fermi mixtures, derive the associated Kohn-Sham equations, and determine the exchange-correlation energy in local density approximation. We solve numerically the Kohn-Sham system and determine the boson and fermion density distributions and the ground-state energy of a trapped, dilute mixture beyond mean-field approximation. The importance of the corrections due to exchange--correlation is discussed by comparison with current experiments; in particular, we investigate the effect of of the repulsive potential energy contribution due to exchange--correlation on the stability of the mixture against collapse.Comment: 6 pages, 4 figures (final version as published in Physical Review

A long term study of axonal transport in the central visual system following eye enucleation in the adult cat.

The effect of the enucleation of one eye on anterograde and retrograde labelling in geniculo-cortical, cortico-geniculate and commissural projections was investigated in adult cats by means of horseradish peroxidase (HRP) and tritiated aminoacids. It was found that in addition to the immediate decrease of retrograde labelling with HRP in the cortical projections from the deafferented A-laminae of the dorsal part of the lateral geniculate nucleus (Singer et al. 1977) there is a further reduction which lasts up to 75 days after enucleation. At 146 and 363 days after enucleation a slight increase in the number of labelled neurones was noted in the deafferented lamina. Qualitative assessment did not reveal any changes of anterograde labelling with tritiated amino acids in geniculo-cortical, cortico-geniculate and commissural axones. In addition, the retrograde labelling with HRP in cortico-geniculate and commissural projections seemed to be unaffected by eye enucleation

Thermodynamics of a Trapped Bose-Fermi Mixture

By using the Hartree-Fock-Bogoliubov equations within the Popov approximation, we investigate the thermodynamic properties of a dilute binary Bose-Fermi mixture confined in an isotropic harmonic trap. For mixtures with an attractive Bose-Fermi interaction we find a sizable enhancement of the condensate fraction and of the critical temperature of Bose-Einstein condensation with respect to the predictions for a pure interacting Bose gas. Conversely, the influence of the repulsive Bose-Fermi interaction is less pronounced. The possible relevance of our results in current experiments on trapped $^{87}{\rm Rb}-^{40}${\rm K} mixtures is discussed.Comment: 5 pages + 4 figures; minor changes, final version to appear in Phys. Rev. A; the extension work on the finite-temperature low-lying excitations can be found in cond-mat/030763

Mixing-Demixing transition in 1D boson-fermion mixture at low fermion densities

We numerically investigated the mixing-demixing transition of the boson-fermion mixture on a 1D lattice at an incommensurate filling with the fermion density being kept below the boson density. The phase diagram we obtained suggested that the decrease of the number of the fermions drove the system into the demixing phase

Controlling ultracold atoms in multi-band optical lattices for simulation of Kondo physics

We show that ultracold atoms can be controlled in multi-band optical lattices through spatially periodic Raman pulses for investigation of a class of strongly correlated physics related to the Kondo problem. The underlying dynamics of this system is described by a spin-dependent fermionic or bosonic Kondo-Hubbard lattice model even if we have only spin-independent atomic collision interaction. We solve the bosonic Kondo-Hubbard lattice model through a mean-field approximation, and the result shows a clear phase transition from the ferromagnetic superfluid to the Kondo-signet insulator at the integer filling.Comment: 4 pages, 2 figure

Quantum field theory of dilute homogeneous Bose-Fermi mixtures at zero temperature: General formalism and beyond mean-field corrections

We consider a dilute homogeneous mixture of bosons and spin-polarized fermions at zero temperature. We first construct the formal scheme for carrying out systematic perturbation theory in terms of single particle Green’s functions. We especially focus on the description of the boson-fermion interaction. To do so we need to introduce the renormalized boson-fermion T matrix, which we determine to second order in the boson-fermion s-wave scattering length. We also discuss how to incorporate the usual boson-boson T matrix in mean field approximation to obtain the total ground-state properties of the system. The next-order term beyond mean field stems from the boson-fermion interaction and is proportional to aBFkF. The total ground-state energy density to this order is the sum of the kinetic energy of the free fermions, the boson-boson mean-field interaction, the usual mean-field contribution to the boson-fermion interaction energy, and the first boson-fermion correction beyond mean field. We also compute the bosonic and the fermionic chemical potentials, the compressibilities, and the modification to the induced fermion-fermion interaction. We discuss the behavior of the total ground-state energy and the importance of the correction beyond mean field for various parameter regimes, in particular considering mixtures of 6Li and 7Li and of 3He and 4He. Moreover, we determine the modification of the induced fermion-fermion interaction due to the effects beyond mean field. We show that there is no effect on the depletion of the Bose condensate to first order in the boson-fermion scattering length aBF

Pilot retrofit test of refrigerant R-134a for GDSCC

NASA has issued an interim policy requiring all of its Centers to eliminate consumption (purchase) of stratospheric ozone-depleting substances, including chlorofluorocarbons (CFC's), by 1995. Also, plans must be outlined for the eventual phase out of their usage. The greatest source of CFC consumption and usage at the Goldstone Deep Space Communications Complex is refrigerant R-12, which is used in many of the facility's air-conditioning systems. A pilot retrofit test shows that retrofitting R-12 air-conditioning systems with hydrofluorocarbon R-13a would be a workable means to comply with the R-12 portion of NASA's policy. Results indicate acceptable cost levels and nearly equivalent system performance

Mixtures of Bosonic and Fermionic Atoms in Optical Lattices

We discuss the theory of mixtures of Bosonic and Fermionic atoms in periodic potentials at zero temperature. We derive a general Bose--Fermi Hubbard Hamiltonian in a one--dimensional optical lattice with a superimposed harmonic trapping potential. We study the conditions for linear stability of the mixture and derive a mean field criterion for the onset of a Bosonic superfluid transition. We investigate the ground state properties of the mixture in the Gutzwiller formulation of mean field theory, and present numerical studies of finite systems. The Bosonic and Fermionic density distributions and the onset of quantum phase transitions to demixing and to a Bosonic Mott--insulator are studied as a function of the lattice potential strength. The existence is predicted of a disordered phase for mixtures loaded in very deep lattices. Such a disordered phase possessing many degenerate or quasi--degenerate ground states is related to a breaking of the mirror symmetry in the lattice.Comment: 11 pages, 8 figures; added discussions; conclusions and references expande

What can patients do to facilitate shared decision making? A qualitative study of patients with depression or schizophrenia and psychiatrists

Purpose Patient involvement in decision making is endorsed by patients and professionals. While research has recently been conducted on how professionals can promote shared decision making (SDM), little is known about how patients can also facilitate SDM. Methods Seven focus groups were conducted: 3 with psychiatrists and 4 with patients with schizophrenia or depression. The focus groups were transcribed and independently coded line by line by 2 researchers. Data were analyzed using content analysis. Results Seven themes related to patient attitudes and behaviors were identified: honesty and openness with one’s psychiatrist and oneself, trust in one’s psychiatrist and patience with the treatment, respect and politeness, informing the psychiatrist and giving feedback, engagement/active participation during the consultation, gathering information/preparing for the consultation and implementing decisions. Barriers (e.g., avolition, lack of decisional capacity, powerlessness during involuntary treatment) and facilitators of active patient behavior were also identified. Conclusions There are various ways in which patients can facilitate SDM/play a more active role in decision making, with patients emphasizing being open and honest and psychiatrists emphasizing being active in the consultation. Interventions to increase active patient behavior may enhance SDM in mental health care

Quantum phases of atomic boson-fermion mixtures in optical lattices

The zero-temperature phase diagram of a binary mixture of bosonic and fermionic atoms in an one-dimensional optical lattice is studied in the framework of the Bose-Fermi-Hubbard model. By exact numerical solution of the associated eigenvalue problems, ground state observables and the response to an external phase twist are evaluated. The stiffnesses under phase variations provide measures for the boson superfluid fraction and the fermionic Drude weight. Several distinct quantum phases are identified as function of the strength of the repulsive boson-boson and the boson-fermion interaction. Besides the bosonic Mott-insulator phase, two other insulating phases are found, where both the bosonic superfluid fraction and the fermionic Drude weight vanish simultaneously. One of these double-insulator phases exhibits a crystalline diagonal long-range order, while the other is characterized by spatial separation of the two species.Comment: 4 pages, 3 figures, using REVTEX