Counterflow in a doubly superfluid mixture of Bosons and Fermions

In this article, we calculate the friction between two counter-flowing bosonic and fermionic super-fluids. In the limit where the boson-boson and boson-fermion interactions can be treated within the mean-field approximation, we show that the force can be related to the dynamical structure factor of the fermionic component. Finally, we provide asymptotic expressions for weakly and strongly attractive fermions and show that the damping rate obeys simple scaling laws close to the critical velocity.Comment: Submitted to Phys. Rev.

Universal phase diagram of a strongly interacting Fermi gas with unbalanced spin populations

We present a theoretical interpretation of a recent experiment presented in ref. \cite{Zwierlein06} on the density profile of Fermi gases with unbalanced spin populations. We show that in the regime of strong interaction, the boundaries of the three phases observed in \cite{Zwierlein06} can be characterized by two dimensionless numbers $\eta\_\alpha$ and $\eta\_\beta$. Using a combination of a variational treatment and a study of the experimental results, we infer rather precise bounds for these two parameters.Comment: 4 pages, 2 figure

Capillary-gravity waves: a "fixed-depth" analysis

We study the onset of the wave-resistance due to the generation of capillary-gravity waves by a partially immersed moving object in the case where the object is hold at a fixed immersion depth. We show that, in this case, the wave resistance varies continuously with the velocity, in qualitative accordance with recent experiments by Burghelea et al. (Phys. Rev. Lett. 86, 2557 (2001)).Comment: 7 pages, 3 figures, submitted to Europhysics Letter

An Atom Faucet

We have constructed and modeled a simple and efficient source of slow atoms. From a background vapour loaded magneto-optical trap, a thin laser beam extracts a continuous jet of cold rubidium atoms. In this setup, the extraction column that is typical to leaking MOT systems is created without any optical parts placed inside the vacuum chamber. For detailed analysis, we present a simple 3D numerical simulation of the atomic motion in the presence of multiple saturating laser fields combined with an inhomogeneous magnetic field. At a pressure of $P_{\rm Rb87}=1 \times 10^{-8}$ mbar, the moderate laser power of 10 mW per beam generates a jet of flux $\Phi =1.3\times 10^8$ atoms/s with a mean velocity of 14 m/s and a divergence of $<20$ mrad.Comment: Submitted to EPJD. 1 TeX file (EPJ format), 7 picture

Vortex formation in a stirred Bose-Einstein condensate

Using a focused laser beam we stir a Bose-Einstein condensate of 87Rb confined in a magnetic trap and observe the formation of a vortex for a stirring frequency exceeding a critical value. At larger rotation frequencies we produce states of the condensate for which up to four vortices are simultaneously present. We have also measured the lifetime of the single vortex state after turning off the stirring laser beam.Comment: 4 pages, 3 figure

Analisis Komparasi Efektivitas Penjualan Sebelum Dan Sesudah Menggunakan Video Marketing Online Talk Fusion Di Manado

conventional manners of marketing systems that are considered inefficient and ineffective has been replaced by internet marketing which is easier to use, has a wider range of consumers, and provides better result. Social media has started to be used as a growing medium for the promotion of business activities because it has an attractive appearance. This study is conducted to see whether there are differences in effectiveness of sales before and after the usage of Talk Fusion online marketing videos in Manado. The analysis method in this study is comparative research by using paired samples t-test. This study uses 30 respondents who are obtained by using snowball and purposive sampling. The result of this study shows that there are significant differences in the effectiveness of sales before and after the usage of Talk Fusion online marketing videos in Manado. Keywords: sales effectiveness, internet marketing, online marketing video

Achieving one-dimensionality with attractive fermions

In this article we discuss the accuracy of effective one-dimensional theories used to describe the behavior of ultracold atomic ensembles confined in quantum wires by a harmonic trap. We derive within a fully many-body approach the effective Hamiltonian describing this class of systems and we calculate the beyond-mean field corrections to the energy of the ground state arising from virtual transitions towards excited state of the confining potential. We find that, due to the Pauli principle, effective finite-range corrections are one of magnitude larger than effective three-body interactions.By comparing to exact solutions of the purely 1D problem, we conclude that a 1D effective theory provides a good description of the ground state of the system for a rather large range of interaction parameters