Behavior of the anomalous correlation function in uniform 2D Bose gas

We investigate the behavior of the anomalous correlation function in two dimensional Bose gas. In the local case, we find that this quantity has a finite value in the limit of weak interactions at zero temperature. The effects of the anomalous density on some thermodynamic quantities are also considered. These effects can modify in particular the chemical potential, the ground sate energy, the depletion and the superfluid fraction. Our predictions are in good agreement with recent analytical and numerical calculations. We show also that the anomalous density presents a significant importance compared to the non-condensed one at zero temperature. The single-particle anomalous correlation function is expressed in two dimensional homogenous Bose gases by using the density-phase fluctuation. We then confirm that the anomalous average accompanies in analogous manner the true condensate at zero temperature while it does not exist at finite temperature.Comment: 15 pages, 3 figure

Spectral function and quasi-particle damping of interacting bosons in two dimensions

We employ the functional renormalization group to study dynamical properties of the two-dimensional Bose gas. Our approach is free of infrared divergences, which plague the usual diagrammatic approaches, and is consistent with the exact Nepomnyashchy identity, which states that the anomalous self-energy vanishes at zero frequency and momentum. We recover the correct infrared behavior of the propagators and present explicit results for the spectral line-shape, from which we extract the quasi-particle dispersion and damping.Comment: 4 pages, 3 figures, revisited version, to appear as Phys. Rev. Lette

Infrared behavior in systems with a broken continuous symmetry: classical O(N) model vs interacting bosons

In systems with a spontaneously broken continuous symmetry, the perturbative loop expansion is plagued with infrared divergences due to the coupling between transverse and longitudinal fluctuations. As a result the longitudinal susceptibility diverges and the self-energy becomes singular at low energy. We study the crossover from the high-energy Gaussian regime, where perturbation theory remains valid, to the low-energy Goldstone regime characterized by a diverging longitudinal susceptibility. We consider both the classical linear O($N$) model and interacting bosons at zero temperature, using a variety of techniques: perturbation theory, hydrodynamic approach (i.e., for bosons, Popov's theory), large-$N$ limit and non-perturbative renormalization group. We emphasize the essential role of the Ginzburg momentum scale $p_G$ below which the perturbative approach breaks down. Even though the action of (non-relativistic) bosons includes a first-order time derivative term, we find remarkable similarities in the weak-coupling limit between the classical O($N$) model and interacting bosons at zero temperature.Comment: v2) 19 pages, 8 figure

Condensate density of interacting bosons: a functional renormalization group approach

We calculate the temperature dependent condensate density $\rho^0 (T)$ of interacting bosons in three dimensions using the functional renormalization group (FRG). From the numerical solution of suitably truncated FRG flow equations for the irreducible vertices we obtain $\rho^0 (T)$ for arbitrary temperatures. We carefully extrapolate our numerical results to the critical point and determine the order parameter exponent $\beta \approx 0.32$, in reasonable agreement with the expected value $0.345$ associated with the XY-universality class. We also calculate the condensate density in two dimensions at zero temperature using a truncation of the FRG flow equations based on the derivative expansion including cubic and quartic terms in the expansion of the effective potential in powers of the density. As compared with the widely used quadratic approximation for the effective potential, the coupling constants associated with the cubic and quartic terms increase the result for the condensate density by a few percent. However, the cubic and quartic coupling constants flow to rather large values, which sheds some doubt on FRG calculations based on a low order polynomial approximation for the effective potential.Comment: 9 pages, 6 figure

Thermocapillary and shear driven flows in gas/liquid system in annular duct

We report the results of numerical study of two-phase flows in annulus for different aspect ratios obtained in the frame of the JEREMI experiment preparation. The geometry of the physical problem is a cylindrical and non-deformable liquid bridge concentrically surrounded by an annular gas channel under conditions of zero gravity. Thermocapillary (Marangoni) convection in liquid bridge of Pr 68 is analyzed in the case when the interface is subjected to an axial gas stream. The gas flow is counter-directed with respect to the Marangoni flow. The inlet gas velocity U 0 g, temperature difference ΔT between end rods of the liquid bridge and aspect ratio are the control parameters of the system. In the case when the gas stream comes from the cold side, it cools down the interface to a temperature lower than that of the liquid beneath, and in a certain region of the parameter space that cooling causes instability due to a temperature difference in the direction, perpendicular to the interface. The present study is focused on the influence of the aspect ratio on the existence and characteristic features of the oscillatory regime.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

On Marangoni convective patterns driven by an exothermic chemical reaction in two-layer systems

info:eu-repo/semantics/publishe

The Role of Lactobacillus reuteri DSMZ17648 for Helicobacter pylori eradication therapy (Review of literature and advisory council resolution, February 28, 2018)

Aim of review. To analyze the options of application of Lactobacillus reuteri DSMZ17648 (Pylopass™) within Helicobacter pylori eradication. Summary. H. pylori eradication therapy is considered as one of the optional spheres for clinical application of probiotic medications. According to available data certain strains of probiotics are effective in decreasing of gastrointestinal adverse effects rates, associated with eradication therapy while the other can potentiate the efficacy of H. pylori eradication itself. L. reuteri strain DSM17648 which was chosen from over 700 wildtype strains of Lactobacillus spp. possess the ability for selective adhesion to H. pylori in vivo in the gastric media. DSM17648 strain of L. reuteri form coaggregates with various H. pylori strains and serotypes both in vivo and in vitro. It was revealed that lyophilizate of this strain (PylopassTM) blocks adhesion of H. pylori to epithelial cells as well. Clinical trials demonstrate the effect of PylopassTMon gastric mucosa colonization by H. pylori according to the 13C urea breath test data and as well the increase in H. pylori eradication rate when the productis added the to triple therapy modes. Conclusion. Potential of PylopassTM combination to various H. pylori eradication therapy modes is a subject offutnet multicenter randomized clinical trials for assessment of optimal combination to antibiotic drugs, treatment duration and adverse effect rates. The value of monotherapy by this metabiotic at chronic H. pyloriassociated gastritis is a subject of further studies