Two component Bose-Hubbard model with higher angular momentum states

We study a Bose-Hubbard Hamiltonian of ultracold two component gas of spinor Chromium atoms. Dipolar interactions of magnetic moments while tuned resonantly by ultralow magnetic field can lead to spin flipping. Due to approximate axial symmetry of individual lattice site, total angular momentum is conserved. Therefore, all changes of the spin are accompanied by the appearance of the angular orbital momentum. This way excited Wannier states with non vanishing angular orbital momentum can be created. Resonant dipolar coupling of the two component Bose gas introduces additional degree of control of the system, and leads to a variety of different stable phases. The phase diagram for small number of particles is discussed.Comment: 4 pages, 2 figure

On the stability of Bose-Fermi mixtures

We consider the stability of a mixture of degenerate Bose and Fermi gases. Even though the bosons effectively repel each other the mixture can still collapse provided the Bose and Fermi gases attract each other strongly enough. For a given number of atoms and the strengths of the interactions between them we find the geometry of a maximally compact trap that supports the stable mixture. We compare a simple analytical estimation for the critical axial frequency of the trap with results based on the numerical solution of hydrodynamic equations for Bose-Fermi mixture.Comment: 4 pages, 3 figure

Statistical properties of one dimensional attractive Bose gas

Using classical field approximation we present the first study of statistical properties of one dimensional Bose gas with attractive interaction. The canonical probability distribution is generated with the help of a Monte Carlo method. This way we obtain not only the depletion of the condensate with growing temperature but also its fluctuations. The most important is our discovery of a reduced coherence length, the phenomenon observed earlier only for the repulsive gas, known as quasicondensation.Comment: 4 pages, 4 figure

Activity of Dehydrogenases as an Indicator of Soil Environment Quality

Activity of dehydrogenases (DHs) indicates the presence of viable and physiologically active (physiologically active or physiological activity) microorganisms. Their presence (activity) in soil is correlated with the content of organic carbon, microorganisms, nitrifying activity and microbial respiration. Determination of DHs activity allows to control changes in soil microbial population and is considered as an important parameter of soil quality. The aim of the study was to determine the effects of different farming systems on the enzymatic activity in soil under winter wheat. The research was conducted in the years 2014–2016 on long-term field experiment under two different farming systems (ecological and conventional) at the IUNG (PIB) Experimental Station located in Osiny (Lublin Voivodeship), Poland. Each farming system differs in crop rotation system and whole agrotechnics, which have been adapted to its specificity. Determination of DHs activity was performed using Casida et al.’s (1964) method with modifications. Measured DHs activity was expressed in milligrams of triphenyl formazan (TPF) per 100 g of soil within 24 hours. The results showed that ecological farming system beneficially influenced soil environment.

Correlations in atomic systems: Diagnosing coherent superpositions

While investigating quantum correlations in atomic systems, we note that single measurements contain information about these correlations. Using a simple model of measurement -- analogous to the one used in quantum optics -- we show how to extract higher order correlation functions from individual "phtotographs" of the atomic sample. As a possible application we apply the method to detect a subtle phase coherence in mesoscopic superpostitions.Comment: 4 pages, 2 figures, provisionally accepted to Physical Review Letter

Free expansion of a Bose-Einstein condensate at the presence of a thermal cloud

We investigate numerically the free-fall expansion of a $^{87}$Rb atoms condensate at nonzero temperatures. The classical field approximation is used to separate the condensate and the thermal cloud during the expansion. We calculate the radial and axial widths of the expanding condensate and find clear evidence that the thermal component changes the dynamics of the condensate. Our results are confronted against the experimental data