724 research outputs found
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 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
- …