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Elastic Enhancement Factor: Mesoscopic Systems versus Macroscopic 2D Electromagnetic Analogue Devices

100%
Sokolov V., Zhirov O.
Acta Physica Polonica A
|
2015
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vol. 128
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issue 6
990-993
EN
Excess of probabilities of the elastic processes over the inelastic ones is a common feature of the resonance phenomena described in the framework of the random matrix theory. This effect is quantitatively characterized by the elastic enhancement factor F^{(β)} that is the typical ratio of elastic and inelastic cross-sections. Being measured experimentally, this quantity can supply us with information on specific features of the dynamics of the intermediate complicated open system. We discuss properties of the enhancement factor in a wide scope from mesoscopic systems to macroscopic analogue electromagnetic resonators and demonstrate essential qualitative distinction between the elastic enhancement factor's peculiarities in these two cases. Complete analytical solution is found for the case of systems without time-reversal symmetry and only a few open equivalent scattering channels.
2
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Atomic Nucleus as Chaotic Quantum Many-Body System

100%
Zelevinsky V.
Acta Physica Polonica A
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2015
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vol. 128
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issue 6
1008-1016
EN
Quantum many-body chaos is described as a practical (theoretical, experimental, and computational) instrument in physics of mesoscopic systems of interacting particles. Using mainly nuclear physics applications, it is shown that interactions of constituents create stationary states of high complexity with respect to the nean-field basis with observable properties smoothly changing along the spectrum. Both local Gaussian orthogonal ensemble type features and the global evolution along the spectrum are used to understand the many-body physics and define thermodynamic properties of isolated mesoscopic objects. Among the examples discussed, especially interesting is a chaotic enhancement of weak perturbations illustrated by a large parity violation in neutron resonances on heavy nuclei. Artificially introduced chaotic elements are used to explore the nuclear landscape and predict phase transformations.
3
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Neutron Resonances: Widths Distribution versus the Porter-Thomas Law

100%
Sokolov V.
Acta Physica Polonica A
|
2017
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vol. 132
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issue 6
1704-1706
EN
The neutron resonance scattering off heavy nuclei is a paradigmatic example of the chaotic processes that are well described within the framework of the standard Random Matrix Theory (RMT). In zero approximation of non-overlapping resonances, the resonance width distribution is given by the standard Porter-Thomas law (PTD) dw/dx= e^{-x/2}/√(2πx), where x=Γ/⟨Γ⟩ is the resonance width measured in the units of its mean value. We analyze the influence of the resonance overlapping and show that the experimentally observed deviations from of the PTD arise due to the influence of a moderate number of neighboring resonances located inside a restricted energy interval within which the mean level spacing D remains constant.
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