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Fermions and Bosons in a Double-Well Potential

100%
Bielas A., Maśka M.
Acta Physica Polonica A
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2014
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vol. 126
|
issue 4a
A-118-A-123
EN
The boson-fermion model, describing a mixture of fermions and bosons is analyzed on a small, two-site lattice. The model includes all the on-site Coulomb-type interactions between bosons, between fermions and between fermions and bosons. Additionally, the Hamiltonian includes a term that describes a conversion of a pair of opposite-spin fermions into a boson and vice versa. We show how this conversion depends on the model parameters.
2
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Aspects of Integrability in a Classical Model for Non-Interacting Fermionic Fields

100%
Grosse-Holz S., Engl T., Richter K., Urbina J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 6
994-1001
EN
In this work we investigate the issue of integrability in a classical model for non-interacting fermionic fields. This model is constructed via classical-quantum correspondence obtained from the semiclassical treatment of the quantum system. Our main finding is that the classical system, contrary to the quantum system, is not integrable in general. Regarding this contrast it is clear that in general classical models for fermionic quantum systems have to be handled with care. Further numerical investigation of the system showed that there may be islands of stability in the phase space. We also investigated a similar model that is used in theoretical chemistry and found this one to be most probably integrable, although also here the integrability is not assured by the quantum-classical correspondence principle.
3
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Harmonically Trapped Bosons on the Sierpiński Carpet

100%
Rovenchak A.
Acta Physica Polonica A
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2010
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vol. 118
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issue 4
531-533
EN
An ideal Bose-gas confined in a harmonic potential is studied. The thermodynamic properties of the said system are obtained in a general case of D dimensions, where D can be fractional (this corresponds to, e.g., porous medium). For the critical temperature, expansions with respect to the number of particles in the system are obtained. Numerical study is made for D = ln8/ln3 corresponding to the dimensionality of the so-called Sierpiński carpet.
4
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Role of Correlations and Off-Diagonal Terms in Binary Disordered One-Dimensional Systems

100%
Kosior A., Major J., Płodzień M., Zakrzewski J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 6
1002-1007
EN
We investigate one-dimensional tight binding model in the presence of a correlated binary disorder. The disorder is due to the interaction of particles with heavy immobile other species. Off-diagonal disorder is created by means of a fast periodic modulation of interspecies interaction. The method based on transfer matrix techniques allows us to calculate the energies of extended modes in the correlated binary disorder. We focus on N-mer correlations and regain known results for the case of purely diagonal disorder. For off-diagonal disorder we find resonant energies. We discuss ambiguous properties of those states and compare analytical results with numerical calculations. Separately we describe a special case of the dual random dimer model.
5
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Tight-Binding Models in a Quasiperiodic Optical Lattice

100%
Jagannathan A., Duneau M.
Acta Physica Polonica A
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2014
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vol. 126
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issue 2
490-492
EN
This paper describes how one can use four standing wave laser fields to realize a two dimensional optical quasicrystal with eight-fold symmetry, closely related to the well-known octagonal or Ammann-Beenker tiling quasicrystal. We describe the structure and we outline the main features of an effective tight-binding model for atoms in this optical quasicrystal. Such a system, if realized experimentally, should provide valuable insights into the quantum properties of quasicrystals.
6
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Investigation of Grooved Circular Jet Flow Experimentally and Using Computational Fluid Dynamics

88%
Inan A., Sisman T.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1145-1149
EN
This study is the investigation of grooved circular jet flow experimentally and using computational fluid dynamics (CFD). Experimental studies were conducted by using straight circular and grooved circular tubes in a multi-purpose low-range subsonic wind tunnel. Single channel hot wire anemometer was used in turbulence measurements. Numerical studies for the solution of jet flow were performed through FLUENT program (ANSYS 14.5). Jet flow profiles at different velocities were formed by using the data generated at predetermined stations in the experiment room for the straight circular tubes and grooved circular tubes. After transferring the experimental data to Fluent, jet exit points of the circular tubes were placed in the quarter model to coincide with the initial coordinates of experimental room. CFD Calculations were done by implementing different velocities in the experimental room and the jet. Jet flow structures obtained from both computational and experimental calculations are shown in graphs and the data is presented in Tables. The obtained parameters are as follows: axis velocity (U_{e}), root mean square velocity (U_{rms}), turbulence velocity (U_{turb}), jet half width (b) and Reynolds numbers (Re_{D} and Re_{b}). These parameters were calculated with reference to jet radius and jet half width. Graphics formed by the generated non-dimensional data were compared to the previous studies.
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