128 research outputs found
The inverse-square interaction phase diagram: unitarity in the bosonic ground state
Ground-state properties of bosons interacting via inverse square potential
(three dimensional Calogero-Sutherland model) are analyzed. A number of
quantities scale with the density and can be naturally expressed in units of
the Fermi energy and Fermi momentum multiplied by a dimensionless constant
(Bertsch parameter). Two analytical approaches are developed: the Bogoliubov
theory for weak and the harmonic approximation (HA) for strong interactions.
Diffusion Monte Carlo method is used to obtain the ground-state properties in a
non-perturbative manner. We report the dependence of the Bertsch parameter on
the interaction strength and construct a Pad\'e approximant which fits the
numerical data and reproduces correctly the asymptotic limits of weak and
strong interactions. We find good agreement with beyond-mean field theory for
the energy and the condensate fraction. The pair distribution function and the
static structure factor are reported for a number of characteristic
interactions. We demonstrate that the system experiences a gas-solid phase
transition as a function of the dimensionless interaction strength. A
peculiarity of the system is that by changing the density it is not possible to
induce the phase transition. We show that the low-lying excitation spectrum
contains plasmons in both phases, in agreement with the Bogoliubov and HA
theories. Finally, we argue that this model can be interpreted as a realization
of the unitary limit of a Bose system with the advantage that the system stays
in the genuine ground state contrarily to the metastable state realized in
experiments with short-range Bose gases.Comment: published version, 27 pages, 6 figures, 1 tabl
Low-dimensional weakly interacting Bose gases: non-universal equations of state
The zero-temperature equation of state is analyzed in low-dimensional bosonic
systems. In the dilute regime the equation of state is universal in terms of
the gas parameter, i.e. it is the same for different potentials with the same
value of the s-wave scattering length. Series expansions of the universal
equation of state are reported for one- and two- dimensional systems. We
propose to use the concept of energy-dependent s-wave scattering length for
obtaining estimations of non-universal terms in the energy expansion. We test
this approach by making a comparison to exactly solvable one-dimensional
problems and find that the generated terms have the correct structure. The
applicability to two-dimensional systems is analyzed by comparing with results
of Monte Carlo simulations. The prediction for the non-universal behavior is
qualitatively correct and the densities, at which the deviations from the
universal equation of state become visible, are estimated properly. Finally,
the possibility of observing the non-universal terms in experiments with
trapped gases is also discussed.Comment: 11 pages, 4 figure
Quasiequilibrium supersolid phase of a two-dimensional dipolar crystal
We have studied the possible existence of a supersolid phase of a
two-dimensional dipolar crystal using quantum Monte Carlo methods at zero
temperature. Our results show that the commensurate solid is not a supersolid
in the thermodynamic limit. The presence of vacancies or interstitials turns
the solid into a supersolid phase even when a tiny fraction of them are present
in a macroscopic system. The effective interaction between vacancies is
repulsive making a quasiequilibrium dipolar supersolid possible.Comment: 5 pages, 4 figure
Development of high sensitive real-time PCR to detect mustard and other allergens of the family Brassicaceae in food samples
Mustard is a commonly used condiment including in production of other food products. As mustard is an allergen, it is necessary to control its presence. The development of PCR test-systems for its detection is complicated by the fact that this condiment can be made from seeds of various plant species (Brassica juncea, Brassica nigra, Sinapis alba) of the family Brassicaceae that are not closely related. This family includes other plant species such as white cabbage (Brassica oleracea) and rapeseed (Brassica napus), which can cause the allergic reaction, although seldom. In this connection, many authors use primers specific to many species of this family, including to allergens, to detect mustard. In this work, we used the similar strategy. To increase sensitivity, primers for the mitochondrial COX gene were selected. To increase PCR stability in analysis of deeply processed products, primers were selected for a region with a length of 61 base pair. In the work, the specificity and sensitivity of the developed PCR method was confirmed. Analyses of different products, including those that underwent deep technological processing, were carried out with these primers. Also, primers were selected to detect white mustard (S. alba). When analyzing products on the presence of white mustard, charac‑ teristic regional preferences were demonstrated: this species is used in manufacturing products mainly in the UK and USA
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