Density and stability in ultracold dilute boson-fermion mixtures

We analyze in detail recent experiments on ultracold dilute ⁸⁷Rb–⁴⁰K mixtures in Hamburg and in Florence within a mean-field theory. To this end we determine how the stationary bosonic and fermionic density profiles in this mixture depend in the Thomas-Fermi limit on the respective particle numbers. Furthermore, we investigate how the observed stability of the Bose-Fermi mixture with respect to collapse is crucially related to the value of the interspecies s-wave scattering length.     

The effect of repulsive interactions on Bose-Einstein condensation

One-dimensional Bose gases that interact via a repulsive two-body interaction and show Bose-Einstein condensation at the free level are studied. It is shown that the introduction of this interaction, however small, destroys the condensate. It is also shown that the free energy of an interacting Bose gas does not depend on the boundary conditions(including attractive boundary conditions) in the van der Waals limit.     

Rotational and rovibrational transitions in the a 1Δ2 and b 1Σ+0+ states of sulfur monoxide radical

ABSTRACT

Sulfur monoxide radical has widely been detected in outer space using ground-state spectroscopy. The a ¹Δ₂ and b ¹Σ⁺₀₊ states of this radical have low excitation energies, and they possibly exist in outer space. In this work, the potential energy curves and dipole moment functions of the two states were evaluated using the complete active space self- consistent field method, followed by the valence internally contracted multireference configuration interaction approach. The transition line positions, oscillator strengths, band transition dipole matrix elements, Einstein A coefficients, and Franck–Condon factors of all transitions were calculated for lower vibrational levels at rotational angular momentum quantum number J up to 150. The transition line positions calculated in this study are in good agreement with the experimental results. The rovibrational transition became noticeably weak at Δυ > 5. Comparing the results of a ¹Δ₂ and b ¹Σ⁺₀₊ states reported in this paper with the previous values, we conclude that these results are the most accurate and complete to date.     

光格中旋量玻色-爱因斯坦凝聚的高阶非线性孤子激发

研究了一维光格中旋量玻色-爱因斯坦凝聚体的高阶非线性作用下的孤子激发,得出了用椭圆积分表示的明孤子解和特定参数条件下的暗孤子解析解,并求得了能量表达式.     

The interaction of three fields in ECE theory: The inverse Faraday effect

The simultaneous interaction of three fundamental fields is illustrated in Einstein Cartan Evans (ECE) theory with reference to the effect of gravitation on the inverse Faraday effect. The three-field interaction in this case is that of the fermionic, electromagnetic and gravitational fields. The interaction of the first two is developed in a well-defined semi-classical approximation of the ECE wave equation and the effect of gravitation incorporated through the index reduced canonical energy momentum density T. The exercise is repeated using the ECE wave equations and a general rule developed for the effect of gravitation on the fermionic, electromagnetic weak and strong fields.     

On Condensations in the Bogoliubov Weakly Imperfect Bose Gas

We show that condensation in the Bogoliubov weakly imperfect Bose gas (WIBG) may appear in two stages. If interaction is such that the pressure of the WIBG does not coincide with the pressure of the perfect Bose gas (PBG), then the WIBG may manifest two kinds of condensations: nonconventional Bose condensation in zero mode, due to the interaction (the first stage), and conventional (generalized) Bose–Einstein condensation in modes next to the zero mode due to the particle density saturation (the second stage). Otherwise the WIBG manifests only the latter kind of condensation.     

Einstein and Brans–Dicke Frames in Multidimensional Cosmology

Inhomogeneous multidimensional cosmological models with a higher-dimensional space-time manifold _{0 i=1} ⁿ M_i (n 1) are in stigated under dimensional reduction to a D ₀-dimensional effective non-minimally coupled -model which generalizes the familiar Brans–Dicke model. The general form of the Einstein frame representation of multidimensional solutions known in the Brans–Dicke frame is given with respect to cosmic synchronous time. As an example, the transformation is demonstrated explicitly for the generalized Kasner solutions where it is shown that solutions in the Einstein frame show no inflation of the external space although they can undergo deflation after the cosmic synchronous time inversion.     

Bose–Einstein condensation in atomic hydrogen

The addition of atomic hydrogen to the set of gases in which Bose–Einstein condensation can be observed expands the range of parameters over which this remarkable phenomenon can be studied. Hydrogen, with the lowest atomic mass, has the highest transition temperature, 50 μK in our experiments. The very weak interaction between the atoms results in a high ratio of the condensate to normal gas densities, even at modest condensate fractions. Using cryogenic rather than laser precooling generates large condensates. Finally, two-photon spectroscopy is introduced as a versatile probe of the phase transition: condensation in real space is manifested by the appearance of a high-density component in the gas, condensation in momentum space is readily apparent in the momentum distribution, and the phase transition line can be delineated by following the evolution of the density of the normal component.