acta physica slovaca

Acta Physica Slovaca 51(2001)
  • Milinski, N., Milinski, E.
    The DC electrical conductivity calculation purely from the dissipative component of the AC conductivity II. Formula for conductors with static scatterers
    Acta Physica Slovaca 51, 211 (2001)

    Abstract: While the first part of this work was devoted to the conceptual and most crucial questions of the $dc$ electrical conductivity , the present second part is devoted to the technical questions of the theory, to elaboration of the concept to the particular systems. The conducting system to be investigated has been defined here by five suppositions (postulates), rather general to include the systems of practical interest, like metals in solid and liquid phase are, and the amorphous conductors, like the alloys and conducting glasses are. A formula for $dc$ conductivity calculation has been derived, which gives  in terms of the matrix elements |<k+q | F |k >|^2, where F is the scattering force, and k+q, k, are the Bloch functions. For the case when Bloch functions are approximated by plane waves, an approximate formula for  has been obtained in a more tractable form. Specific to our concept is the inclusion of an equation constitutive to calculation, which also has been elaborated for the considered system, to the stage suitable for practical application.  calculation in conjunction with the mentioned constitutive equation is the most important innovative element of our concept, and we expect it will lead to substantial advance in research of this subject.

  • Plujko, V.A., Gorbachenko, O.M., Kavatsyuk, M.O.
    Two-body relaxation times in heated nuclei
    Acta Physica Slovaca 51, 231 (2001)

    Abstract: The retardation and temperature effects in two-body collisions are studied. The collision integral with retardation effects is obtained on the base of the Kadanoff-Baym equations for the Green functions in a form with allowance for reaching the local equilibrium system. The collisional relaxation times of collective vibrations are calculated using both the transport approach and the doorway state mechanism with hierarchy of particle-hole configurations in heated nuclei. The relaxation times of the kinetic method are rather weakly dependent on multipolarity of the Fermi surface distortion and on the mode of the collective motion. The dependence of the relaxation times on temperature as well as on frequency of collective vibrations is considered and compared. It is shown that variations of the in-medium two-body cross-sections with energy lead to non-quadratic dependence of the collisional relaxation time both on temperature and on the frequency of the collective motion.

  • Abdel-Aty, M., Ateto, M.
    Pancharatnam phase of an effective two-level atom in a kerr-like medium
    Acta Physica Slovaca 51, 247 (2001)

    Abstract: The influence of Stark shift on the Pancharatnam phase when an ideal cavity is filled with a Kerr-like medium and coupling is affected through a degenerate two-photon process is studied. The exact results are employed to perform a careful investigation of the temporal evolution of atomic inversion and Pancharatnam phase. We invoke the mathematical notion of maximum variation of a function to construct a measure for Pancharatnam phase fluctuations. It is shown that the Pancharatnam phase explicity contains information about the statistics of the field and atomic coherence. It is shown that the addition of the Kerr medium and the Stark shift has an important effect on the properties of the Pancharatnam phase. The results show that, the effect of the Kerr medium and the Stark shift changes the quasiperiod of the Pancharatnam phase evolution. The general conclusions reached are illustrated by numerical results.

  • Sekanina, H., Hledík, S.
    Holographic interferometry using a digital photo-camera
    Acta Physica Slovaca 51, 261 (2001)

    Abstract: The possibilities of running digital holographic interferometry using commonly available compact digital zoom photo-cameras are studied. The recently developed holographic setup, suitable especially for digital photo-cameras equipped with an undetachable object lens, is used. The method described enables a simple and straightforward way of both recording and reconstructing of a digital holographic interferogram. The feasibility of the new method is verified by digital reconstruction of the interferograms acquired, using a numerical code based on the fast Fourier transform. Experimental results obtained are presented and discussed.

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