Mariusz Gajda, Magdalena Zaluska-Kotur, and Jan Mostowski
We study a system of interacting bosons at zero temperature in an atomic trap. Using wave function that models the ground state of interacting bosons we examine the concepts of the order parameter, off-diagonal order and coherence of the system. We suggest that the coherence length becomes much smaller than the size of the system if the number of trapped particles exceeds a certain limit. This behavior is related to the unavoidable existence of two different length scales -- one determined by the external potential and the second one depending on the two-body forces.
Opt. Express 8, 106 (2001)
Nov 9, 2000
Oct 5, 2000
Correlations in financial time series: established versus emerging markets
Eur. Phys. J. B 20, 527 (2001)
M. Beben and A. Orłowski
Long-time correlations in both well-developed and emerging market indexes are studied. The Hurst exponent as well as detrended fluctuations analysis (DFA) are used as technical tools. Some features that seem to be specific for developing markets are discovered and briefly discussed.
M. Beben and A. Orłowski
Long-time correlations in both well-developed and emerging market indexes are studied. The Hurst exponent as well as detrended fluctuations analysis (DFA) are used as technical tools. Some features that seem to be specific for developing markets are discovered and briefly discussed.
Jul 12, 2000
Squeezing of electromagnetic field in a cavity by electrons in Trojan states
Piotr Kochański, Zofia Bialynicka-Birula, and Iwo Bialynicki-Birula
The notion of the Trojan state of a Rydberg electron, introduced by I. Bialynicki-Birula, M. Kaliński, and J. H. Eberly [Phys. Rev. Lett. 73, 1777 (1994)] is extended to the case of an electromagnetic field quantized in a cavity. The shape of the electronic wave packet describing the Trojan state is practically the same as in the previously studied externally driven system. The fluctuations of the quantized electromagnetic field around its classical value exhibit strong squeezing. The emergence of Trojan states in the cylindrically symmetrical system is attributed to spontaneous symmetry breaking.
Phys. Rev. A 63, 013811 (2001)
The notion of the Trojan state of a Rydberg electron, introduced by I. Bialynicki-Birula, M. Kaliński, and J. H. Eberly [Phys. Rev. Lett. 73, 1777 (1994)] is extended to the case of an electromagnetic field quantized in a cavity. The shape of the electronic wave packet describing the Trojan state is practically the same as in the previously studied externally driven system. The fluctuations of the quantized electromagnetic field around its classical value exhibit strong squeezing. The emergence of Trojan states in the cylindrically symmetrical system is attributed to spontaneous symmetry breaking.
Phys. Rev. A 63, 013811 (2001)
Jun 10, 2000
May 30, 2000
Multimode Dynamics of a Coupled Ultracold Atomic-Molecular System
Phys. Rev. Lett. 86, 1397 (2001)
Krzysztof Góral, Mariusz Gajda, and Kazimierz Rzążewski
We analyze the coherent multimode dynamics of a system of coupled atomic and molecular Bose gases. Starting from an atomic Bose-Einstein condensate with a small thermal component, we observe a complete depletion of the atomic and molecular condensate modes on a short time scale due to a significant population of excited states. Giant coherent oscillations between the two condensates for typical parameters are almost completely suppressed. Our results cast serious doubts on the common use of the 2-mode model for the description of coupled ultracold atomic-molecular systems and should be considered when planning future experiments with ultracold molecules.
Krzysztof Góral, Mariusz Gajda, and Kazimierz Rzążewski
We analyze the coherent multimode dynamics of a system of coupled atomic and molecular Bose gases. Starting from an atomic Bose-Einstein condensate with a small thermal component, we observe a complete depletion of the atomic and molecular condensate modes on a short time scale due to a significant population of excited states. Giant coherent oscillations between the two condensates for typical parameters are almost completely suppressed. Our results cast serious doubts on the common use of the 2-mode model for the description of coupled ultracold atomic-molecular systems and should be considered when planning future experiments with ultracold molecules.
May 26, 2000
Cluster explosion in an intense laser pulse: Thomas-Fermi model
Physical Review A 63, 013203 (2001)
Marian Rusek, Herve Lagadec and Thomas Blenski
A refined three-dimensional version of the time-dependent Thomas-Fermi model is used to qualitatively study the explosion of rare-gas atomic clusters in an intense laser field. Clusters as large as 55 atoms are exposed to a strong subpicosecond laser pulse. A stepwise character of the explosion is observed in which atomic shells are expelled sequentially. The role of “hot” electron dynamics in the explosion process is also investigated via initial temperature effects. Contrary to previous opinions it seems that the so-called hydrodynamic explosion scenario is important for most energetic ions coming from the outermost shells only.
Marian Rusek, Herve Lagadec and Thomas Blenski
A refined three-dimensional version of the time-dependent Thomas-Fermi model is used to qualitatively study the explosion of rare-gas atomic clusters in an intense laser field. Clusters as large as 55 atoms are exposed to a strong subpicosecond laser pulse. A stepwise character of the explosion is observed in which atomic shells are expelled sequentially. The role of “hot” electron dynamics in the explosion process is also investigated via initial temperature effects. Contrary to previous opinions it seems that the so-called hydrodynamic explosion scenario is important for most energetic ions coming from the outermost shells only.
May 18, 2000
New concept of waveguide for inverse free electron laser accelerator
Władysław Żakowicz
A segmented waveguide formed by a periodic system of pairs of wedge prisms with a gap between them is proposed. The prisms are made of single-crystal sapphire for which the refraction index ν<1 for CO2 laser radiation (λ=10.6 μm). The attenuation of 0.1 db/m can be estimated for a 5 mm diameter radiation beam for which the Rayleigh distance is approximately 1 m. The gap between adjacent prisms can be useful in FEL-like applications.
Nucl. Instr. Meth. Phys. Res. A 445, 313 (2000)
A segmented waveguide formed by a periodic system of pairs of wedge prisms with a gap between them is proposed. The prisms are made of single-crystal sapphire for which the refraction index ν<1 for CO2 laser radiation (λ=10.6 μm). The attenuation of 0.1 db/m can be estimated for a 5 mm diameter radiation beam for which the Rayleigh distance is approximately 1 m. The gap between adjacent prisms can be useful in FEL-like applications.
Nucl. Instr. Meth. Phys. Res. A 445, 313 (2000)
Apr 24, 2000
Destruction of a Bose-Einstein condensate by strong interactions
Mariusz Gajda, Magdalena A Zaluska-Kotur and Jan Mostowski
We study an exactly solvable system of trapped bosonic particles interacting by model harmonic forces. The model allows for a detailed examination of the order parameter (condensate wavefunction) as well as a concept of the off-diagonal and diagonal order. We analyse the effect of interactions on the condensate and show that sufficiently strong interactions (attractive or repulsive) lead to the destruction of the condensate. In the thermodynamic limit this destruction has a critical character. It is shown that the existence of the coherent state of bosons is related to the existence of two length scales determined by one- and two-particle reduced density matrices. The condensate can exist only if the two length scales are of the same order. Interactions, both repulsive and attractive, change their relative size which may lead to destruction of coherence in the system and depletion of the condensate. We suggest that this scenario is model independent.
J. Phys. B 33, 4003 (2000)
We study an exactly solvable system of trapped bosonic particles interacting by model harmonic forces. The model allows for a detailed examination of the order parameter (condensate wavefunction) as well as a concept of the off-diagonal and diagonal order. We analyse the effect of interactions on the condensate and show that sufficiently strong interactions (attractive or repulsive) lead to the destruction of the condensate. In the thermodynamic limit this destruction has a critical character. It is shown that the existence of the coherent state of bosons is related to the existence of two length scales determined by one- and two-particle reduced density matrices. The condensate can exist only if the two length scales are of the same order. Interactions, both repulsive and attractive, change their relative size which may lead to destruction of coherence in the system and depletion of the condensate. We suggest that this scenario is model independent.
J. Phys. B 33, 4003 (2000)
Apr 13, 2000
Symmetries and modes of wave fields in inhomogeneous media
J. Phys. A 33, 4779 (2000)
Maciej Janowicz
In this paper the 2D Helmholtz equation with space-dependent dielectric permittivity and/or magnetic permeability is considered. The structure of the determining equations for the symmetry generator is analysed. It allows one to find many nontrivial spatial profiles of dielectric functions for which one can still separate variables in both the Helmholtz equation and corresponding Hamilton-Jacobi equation. For the case of the Dirichlet problem of the half-plane in an inhomogeneous medium the diffractive modes of the field are characterized. Several specific examples are provided.
Maciej Janowicz
In this paper the 2D Helmholtz equation with space-dependent dielectric permittivity and/or magnetic permeability is considered. The structure of the determining equations for the symmetry generator is analysed. It allows one to find many nontrivial spatial profiles of dielectric functions for which one can still separate variables in both the Helmholtz equation and corresponding Hamilton-Jacobi equation. For the case of the Dirichlet problem of the half-plane in an inhomogeneous medium the diffractive modes of the field are characterized. Several specific examples are provided.
Apr 5, 2000
Novel quantum effects in light scattering from cold trapped atoms
A. Orlowski, M. Gajda, P. Krekora, R. J. Glauber and J. Mostowski
Both far off-resonance and resonant scattering of light from single atoms trapped by 3D harmonic potentials has thoroughly been studied. Novel effects are predicted for different physical regimes. We have shown that dynamics of the atomic center-of-mass strongly influences the scattering cross section. Possibility of using spectrum of the scattered light in far-off-resonance regime to nondestructively measure the temperature of ultracold atoms is advocated: off-resonance scattering can be used as an ‘optical thermometer’. The realistic Compton-like regime in resonant scattering has been investigated in detail. Another interesting quantum effect in resonant regime, which has not been discussed here due to the lack of space, is the time resolved scattering, showing up when the atom can remain in the excited state long enough to make many trips back and forth in the trap before emitting a photon. The possibility of the experimental observation of the predicted effects is now being scrutinized.
Quantum Communication, Computing, and Measurement 2
Both far off-resonance and resonant scattering of light from single atoms trapped by 3D harmonic potentials has thoroughly been studied. Novel effects are predicted for different physical regimes. We have shown that dynamics of the atomic center-of-mass strongly influences the scattering cross section. Possibility of using spectrum of the scattered light in far-off-resonance regime to nondestructively measure the temperature of ultracold atoms is advocated: off-resonance scattering can be used as an ‘optical thermometer’. The realistic Compton-like regime in resonant scattering has been investigated in detail. Another interesting quantum effect in resonant regime, which has not been discussed here due to the lack of space, is the time resolved scattering, showing up when the atom can remain in the excited state long enough to make many trips back and forth in the trap before emitting a photon. The possibility of the experimental observation of the predicted effects is now being scrutinized.
Quantum Communication, Computing, and Measurement 2
Jan 27, 2000
Spontaneous emission in the presence of a dielectric cylinder
Władysław Żakowicz and Maciej Janowicz
Spontaneous emission of photons by an atom placed near a dielectric cylindrical waveguide at an arbitrary position is analyzed using global free electromagnetic modes, satisfying necessary continuity conditions at the slab boundaries. These modes include the modes extended over the whole space (travelling) and the modes trapped to a waveguide (waveguided). To describe angular properties of the spontaneous emission, a parametrization of the travelling modes by the outgoing waves has been proposed. Angular characteristics of the travelling photon emission, distributions of the trapped photon emission, as well as the global decay rates have been calculated using the quantum approach and the standard perturbation theory. Difficulties due to the presence of sharp resonances (whispering gallery modes) among the travelling photons are pointed out.
Phys. Rev. A 62, 013820 (2000)
Spontaneous emission of photons by an atom placed near a dielectric cylindrical waveguide at an arbitrary position is analyzed using global free electromagnetic modes, satisfying necessary continuity conditions at the slab boundaries. These modes include the modes extended over the whole space (travelling) and the modes trapped to a waveguide (waveguided). To describe angular properties of the spontaneous emission, a parametrization of the travelling modes by the outgoing waves has been proposed. Angular characteristics of the travelling photon emission, distributions of the trapped photon emission, as well as the global decay rates have been calculated using the quantum approach and the standard perturbation theory. Difficulties due to the presence of sharp resonances (whispering gallery modes) among the travelling photons are pointed out.
Phys. Rev. A 62, 013820 (2000)
Jan 14, 2000
Interaction of a hydrogen atom with an intense pulse of vacuum ultraviolet radiation
J. Phys. B 33, 1271 (2000)
Mariusz Gajda, Jacek Krzywinski, Lukasz Plucinski and Bernard Piraux
The free electron laser (FEL) which is currently under construction at the DESY laboratory should deliver a photon beam in the vacuum ultraviolet (VUV) range. Coherent radiation of the FEL will soon allow for testing of the matter-electromagnetic field interaction under very exotic conditions. In this paper we study the ionization of a hydrogen atom by the intense (about 1016 W cm-2 ) beam of photons with energies of 17 eV. We compare exact numerical results with predictions of the perturbation theory showing the limits of its applicability and discussing requirements for the FEL pulse parameters which are necessary for observation of non-perturbative phenomena.
Mariusz Gajda, Jacek Krzywinski, Lukasz Plucinski and Bernard Piraux
The free electron laser (FEL) which is currently under construction at the DESY laboratory should deliver a photon beam in the vacuum ultraviolet (VUV) range. Coherent radiation of the FEL will soon allow for testing of the matter-electromagnetic field interaction under very exotic conditions. In this paper we study the ionization of a hydrogen atom by the intense (about 1016 W cm-2 ) beam of photons with energies of 17 eV. We compare exact numerical results with predictions of the perturbation theory showing the limits of its applicability and discussing requirements for the FEL pulse parameters which are necessary for observation of non-perturbative phenomena.
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