Mirosław Brewczyk, Peter Borowski, Mariusz Gajda and Kazimierz Rzążewski
A classical field approximation to the finite temperature microcanonical thermodynamics of weakly interacting Bose gases is applied to the idealized case of atoms confined in a box with periodic boundary conditions. The whole isolated system is described by a set of classical amplitudes. We show that if the system is in equilibrium the classical amplitudes follow the equipartition theorem which allows us to assign a unique temperature to each given energy state. We also analyse the spectral properties of classical amplitudes and obtain nonperturbative results for the chemical potential as well as temperature-dependent Bogoliubov frequencies and their damping rates. Where available, we make comparison with the analytical estimates of these quantities.
J. Phys. B: At. Mol. Opt. Phys. 37 2725-2738
May 17, 2004
May 7, 2004
Dynamics of Argon Clusters in an Intense Laser Pulse: Bloch-Like Hydrodynamic Model
M. Rusek and A. Orłowski
The dynamics of small (≤55 atoms) argon clusters ionized by an intense, infrared, femtosecond laser pulse is studied using a Bloch-like hydrodynamic model. Evolution of both free electrons and ions formed in the cluster explosion process is examined. Oscillations of the electron cloud in a rare-gas atomic cluster are described as a motion of a fluid obeying Bloch-like hydrodynamic equations. Our theoretical approach includes all possible ionization mechanisms: tunnel (or field) ionization both by an external laser field, and by an internal field due to the space-charge distribution inside the cluster, as well as electron-impact (or collisional) ionization. The results of our simulations are compared both with experimental findings and with predictions of other theoretical models.
Acta Phys. Polonica A, Vol. 106 No 1
The dynamics of small (≤55 atoms) argon clusters ionized by an intense, infrared, femtosecond laser pulse is studied using a Bloch-like hydrodynamic model. Evolution of both free electrons and ions formed in the cluster explosion process is examined. Oscillations of the electron cloud in a rare-gas atomic cluster are described as a motion of a fluid obeying Bloch-like hydrodynamic equations. Our theoretical approach includes all possible ionization mechanisms: tunnel (or field) ionization both by an external laser field, and by an internal field due to the space-charge distribution inside the cluster, as well as electron-impact (or collisional) ionization. The results of our simulations are compared both with experimental findings and with predictions of other theoretical models.
Acta Phys. Polonica A, Vol. 106 No 1
Apr 14, 2004
Soliton Trains in Bose-Fermi Mixtures
T. Karpiuk, M. Brewczyk, S. Ospelkaus-Schwarzer, K. Bongs, M. Gajda, and K. Rzążewski
We theoretically consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases. While we assume the forces between atoms in a pure Bose component to be effectively repulsive, their character can be changed from repulsive to attractive in the presence of fermions provided the Bose and Fermi gases attract each other strongly enough. In such a regime the Bose component becomes a gas of effectively attractive atoms. Hence, generating bright solitons in the bosonic gas is possible. Indeed, after a sudden increase of the strength of attraction between bosons and fermions (realized by using a Feshbach resonance technique or by firm radial squeezing of both samples) soliton trains appear in the Bose-Fermi mixture.
Phys. Rev. Let.Vol. 93 Issue 10
We theoretically consider the formation of bright solitons in a mixture of Bose and Fermi degenerate gases. While we assume the forces between atoms in a pure Bose component to be effectively repulsive, their character can be changed from repulsive to attractive in the presence of fermions provided the Bose and Fermi gases attract each other strongly enough. In such a regime the Bose component becomes a gas of effectively attractive atoms. Hence, generating bright solitons in the bosonic gas is possible. Indeed, after a sudden increase of the strength of attraction between bosons and fermions (realized by using a Feshbach resonance technique or by firm radial squeezing of both samples) soliton trains appear in the Bose-Fermi mixture.
Phys. Rev. Let.Vol. 93 Issue 10
Mar 30, 2004
Explosion of Atom Clusters in a Free-Electron Intense Laser Pulse
M. Rusek and A. Orłowski
The explosion of rare-gas atomic clusters induced by short, intense X-ray pulses generated by a free-electron laser is studied. A numerical approach for an explicitly time-dependent description of small to medium size clusters in 3D is developed within the Thomas--Fermi model. Such an approach, though strongly simplified in comparison to fully quantum-mechanical schemes, is nevertheless expected to yield a qualitatively correct description of the electronic and ionic dynamics of these systems, at a much lower computational cost.
Acta Phys. Polonica A, Vol.105 No. 5
The explosion of rare-gas atomic clusters induced by short, intense X-ray pulses generated by a free-electron laser is studied. A numerical approach for an explicitly time-dependent description of small to medium size clusters in 3D is developed within the Thomas--Fermi model. Such an approach, though strongly simplified in comparison to fully quantum-mechanical schemes, is nevertheless expected to yield a qualitatively correct description of the electronic and ionic dynamics of these systems, at a much lower computational cost.
Acta Phys. Polonica A, Vol.105 No. 5
Mar 18, 2004
Jan 5, 2004
Scattering of plane wave packets by a rigid cylinder: a contribution to the quantum scattering theory
Władysław Żakowicz
Time-dependent scattering of finite duration wave packets on a rigid cylinder is studied using exact solutions of the corresponding Schrödinger equation. The similarity between the time evolution of the total wavefunction and evolution of the corresponding classical ensemble of particles is exposed. Special attention is paid to a discussion of the differences between the total wavefunction dynamics and the dynamics of the scattered part of the wavefunction, the part which is commonly used for the evaluation of scattering cross-sections. This discussion emphasizes the necessity of using the total wavefunction in the description of scattering.
J. Phys. B: At. Mol. Opt. Phys. 37 L153-L159
Time-dependent scattering of finite duration wave packets on a rigid cylinder is studied using exact solutions of the corresponding Schrödinger equation. The similarity between the time evolution of the total wavefunction and evolution of the corresponding classical ensemble of particles is exposed. Special attention is paid to a discussion of the differences between the total wavefunction dynamics and the dynamics of the scattered part of the wavefunction, the part which is commonly used for the evaluation of scattering cross-sections. This discussion emphasizes the necessity of using the total wavefunction in the description of scattering.
J. Phys. B: At. Mol. Opt. Phys. 37 L153-L159
Dec 26, 2003
Fluctuation dynamics of exchange rates on Polish financial market.
A. Orłowski, Z.R. Struzik, E. Syczewska and M.A. Załuska-Kotur
We show results of local fluctuation analysis, probability distributions, and fractional integration analysis for nominal exchange rates of the Polish zloty versus two foreign currencies (US dollar and German mark/euro). The results confirm the rapid change of the volatility pattern in August 1997. We compare the type of the fluctuation behavior before and after this date.
Physica A. 344, Issues 1-2,
We show results of local fluctuation analysis, probability distributions, and fractional integration analysis for nominal exchange rates of the Polish zloty versus two foreign currencies (US dollar and German mark/euro). The results confirm the rapid change of the volatility pattern in August 1997. We compare the type of the fluctuation behavior before and after this date.
Physica A. 344, Issues 1-2,
Dec 15, 2003
Application of the ultrametric distance to portfolio taxonomy. Critical approach and comparison with other methods
Urszula Skórnik-Pokarowska and Arkadiusz Orłowski
We calculate the ultrametric distance between the pairs of stocks that belong to the same portfolio. The ultrametric distance allows us to distinguish groups of shares that are related. In this way, we can construct a portfolio taxonomy that can be used for constructing an efficient portfolio. We also construct a portfolio taxonomy based not only on stock prices but also on economic indices such as liquidity ratio, debt ratio and sales profitability ratio. We show that a good investment strategy can be obtained by applying to the portfolio chosen by the taxonomy method the so-called Constant Rebalanced Portfolio.
Physica A. Vol. 344, Issues 1-2
We calculate the ultrametric distance between the pairs of stocks that belong to the same portfolio. The ultrametric distance allows us to distinguish groups of shares that are related. In this way, we can construct a portfolio taxonomy that can be used for constructing an efficient portfolio. We also construct a portfolio taxonomy based not only on stock prices but also on economic indices such as liquidity ratio, debt ratio and sales profitability ratio. We show that a good investment strategy can be obtained by applying to the portfolio chosen by the taxonomy method the so-called Constant Rebalanced Portfolio.
Physica A. Vol. 344, Issues 1-2
Nov 22, 2003
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