From Randomness to Periodicity --- the Effect of Polarization in the Minority Game Strategy Space

M. Zaluska-Kotur

Properties and behavior of modified minority game are analyzed. It appears that results of the game depend strongly on the way how we draw strategies for players. The probability that given strategy will be chosen is determined by the polarization parameter P. This parameter differs between strategies that go along or against the existing market trend. Strong polarization of the space leads to the periodic dynamics and, finally, for negative P values to the domination of the single strategy in the system. When P is changed the variability of the process decreases, showing kind of the phase transition region. The dependence of the variability on the polarization parameter can be understood on the basis of the crowd--anticrowd theory.


Acta Phys B Vol. 36, No. 8, (2005)

Emission of Thermally Activated Electrons from Rare Gas Clusters Irradiated with Intense VUV Light Pulses from a Free Electron Laser

Laarmann T, Rusek M, Wabnitz H, Schulz J, de Castro AR, Gürtler P, Laasch W, Möller T

The ionization dynamics of Ar and Xe clusters irradiated with intense vacuum ultraviolet light from a free-electron laser is investigated using photoelectron spectroscopy. Clusters comprising between 70 and 900 atoms were irradiated with femtosecond pulses at 95 nm wavelength (~13 eV photon energy) and a peak intensity of ~4×1012 W/cm2. A broad thermal distribution of emitted electrons from clusters with a maximum kinetic energy up to 30–40 eV is observed. The observation of relatively low-energy photoelectrons is in good agreement with calculations using a time-dependent Thomas-Fermi model and gives experimental evidence of an outer ionization process of the clusters, due to delayed thermoelectronic emission.

Phys Rev Lett. 2005 Aug 5;95(6):063402. Epub 2005 Aug 5

Phase fluctuations of a Bose-Einstein condensate in low-dimensional geometry

Demascoth Kadio, Mariusz Gajda and Kazimierz Rzążewski

We investigate the phase fluctuations of a Bose-Einstein condensate in one- (1D) and three-dimensional (3D) elongated harmonic traps with the help of the numerical simulation using classical field approximation. By calculating the eigenvalues of the one-dimensional single-particle density matrix we show that the phase fluctuations of a Bose-Einstein Condensate in a 1D system are due to the thermal low-energy excitations. We find that the phase fluctuations depend on the temperature as has been predicted [Phys. Rev. Lett. 85, 3745 (2000), Phys. Rev. Lett. 87, 050404 (2001)]. Finally we show that the phase coherence length of a condensate in a harmonic trap depends on the aspect ratio of anisotropy (geometry) of the trap. We determine the border between the 3D and quasi-one-dimensional systems by calculating the phase coherence length of the condensate.

Phys. Rev. A 72, 013607 (2005)

Criterion for Bose-Einstein condesation in a harmonic trap in the case with attractive interactions

Mariusz Gajda

Using a model many-body wave function I analyze the standard criterion for Bose-Einstein condensation and its relation to coherence properties of the system. I pay special attention to an attractive condensate under such a condition that a characteristic length scale of the spatial extension of its center of mass differs significantly from length scales of relative coordinates. I show that although no interference fringes are produced in the two-slit Young interference experiment performed on this system, fringes of a high visibility can be observed in a conditional simultaneous detection of two particles.

Phys. Rev. A vol. 73, 023603 - 1-5 (2006) [1/1]

On the stability of Bose-Fermi mixtures

T Karpiuk, M Brewczyk, M Gajda and K Rzążewski

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 the Bose–Fermi mixture.

J. Phys. B: At. Mol. Opt. Phys. 38 L215-L221

Semi-classical approaches to the ion-atom scattering

Maciej Janowicz, Katarzyna Słabkowska, Piotr Matuszak and Marek Polasik

Three semi-classical approaches to the simulation of ion–atom scattering: the Kirschbaum–Wilets, the Cohen energy-bounded, and the wave-packet – are used to calculate the ionization and charge-transfer cross sections for the scattering of fully stripped sulfur ions on atomic hydrogen. Their comparison in the high-energy regime is provided. Elements of microscopic analysis of Kirschbaum–Wilets trajectories are given.

Nuclear Instruments and Methods in Physics Research Section B Vol 235, 1-4, (2005)

Different mechanisms of cluster explosion within an unified time-dependent Thomas-Fermi approach: optical and short-wavelength regimes compared

Marian Rusek and Arkadiusz Orlowski

The dynamics of small (55 atoms) argon clusters ionized by an intense femtosecond laser pulse is studied using a time-dependent Thomas-Fermi model. The resulting Bloch-like hydrodynamic equations are solved numerically using the smooth particle hydrodynamics method without the necessity of grid simulations. As follows from recent experiments, absorption of radiation and subsequent ionization of clusters observed in the short-wavelength laser frequency regime (98 nm) differs considerably from that in the optical spectral range (800 nm). Our theoretical approach provides a unified framework for treating these very different frequency regimes and allows for a deeper understanding of the underlying cluster explosion mechanisms. The results of our analysis following from extensive numerical simulations presented in this paper are compared both with experimental findings and with predictions of other theoretical models.

Phys. Rev. A 71, 043202 (2005)

Trojan States of Electrons Guided by Bessel Beams

Iwo Bialynicki-Birula, Zofia Bialynicka-Birula and Bartosz Chmura

Previous work [I. Bialynicki-Birula, Phys. Rev. Lett. {\bf 93}, 20402 (2004)] is extended to cover more realistic examples of electromagnetic waves, viz. the Bessel beams. It is shown that electrons may be guided by a Bessel beam with nonvanishing orbital angular momentum. The mechanism for trapping the electrons near the electromagnetic vortex line of such a wave field is the same as for the Trojan states of Rydberg electrons produced by a circularly polarized wave. The main difference is that in the present case the transverse motion of electrons in a beam is confined under the action of the electromagnetic wave alone, no additional attraction center is required. We also discuss briefly the motion of electrons in Neumann and Hankel beams.

Physics/0502025 (February 2005)

Free Electrons Generation in the Interaction of Intense Laser Pulses with Atomic Clusters

M. Rusek and A. Orłowski

Interaction of argon clusters with intense laser pulses is studied theoretically. Free electrons energy distribution is studied. Differences between infrared and vacuum ultraviolet frequency regimes are pointed out. Clear physical interpretation of the obtained results is given.

ACTA PHYS. POLONICA A Vol. 107 (2005)

Probabilistic models of income distributions.

Piotr Łukasiewicz and Arkadiusz Orłowski

The results showing relationships between distributions of individual incomes and incomes of two-earners households are presented. It is shown that individual incomes are very well described by Dagum's distributions. Income distributions in two quite different countries (USA and Poland) are studied for comparison. Obtained results show very striking and interesting differences.

Physica A Vol. 344, 1-2