Acta Physica Slovaca 49 (1999)
Kh. Noucier, L. Chetouani
Coherent state propagator for a class of quadratic time-dependent systems
Acta Physica Slovaca 49, 905 (1999)
Abstract: An exact coherent state path integral treatment of a class of quadratic time-dependent systems is proposed. The introduction of auxiliary phase space path integrals maps the original problem to that of a particle in a constant magnetic field and an external time-dependent force. The degenerate parametric amplifier with classical pumping mode is considered to illustrate the formalism.
M. Mansour, M. El Falaki
On the quantum Virasoro algebra
Acta Physica Slovaca 49, 915 (1999)
Abstract: We give the quantum algebra structure on the and deformed Virasoro algebra with its realization in term of the infinite matrix algebra elements.
I.V. Kuzmenko, V.M. Rozenbaum
Spectral line shape of high-frequency local vibrations in adsorbed molecular lattices
Acta Physica Slovaca 49, 921 (1999)
Abstract: We consider high-frequency local vibrations anharmonically coupled with low-frequency modes in a planar lattice of adsorbed molecules. The effect of lateral intermolecular interactions on the spectral line shape for local vibrations is analyzed in the limit of the high density of adsorbed molecules. It is shown that the spectral line positions and widths depend on behaviour of low-frequency distribution function for a system of adsorbed molecules. The results obtained allows the spectral line characteristics of the local vibrations for isotopically diluted C O molecules in the C O monolayer on the NaCl(100) surface to be described in agreement with the experimentally measured values.
Rightly normalized end-to-end distribution function of partially flexible polymers
Acta Physica Slovaca 49, 927 (1999)
Abstract: A normalization problem is discussed, regarding the use of the Green function in the statistical theory of configurations of a `partially flexible polymer' of length thermalized with its environment. The polymer is defined with a (constant) stiffness parameter . The Green function is expressed as a path-integral with paths in a 6-dimensional space , . The basic question which the author analyzes in detail is the accommodation of the Green function with the concept of the end-to-end probability density defined under the constraints . The vectors , and the unit vectors , define, respectively, the positions and the tangential directions of the polymer ends. ( , , , .) An explicit expression for is derived as a function of the stiffness parameter and the temperature . An exact formula is derived for the mean-square end-to-end distance as a function of and . A thorough description is presented concerning the statistics of the tangential direction of the polymer end with provided that the tangential direction is given. When elucidating this statistics, a special attention is devoted to very stiff polymers for which the author defines the `paraxial approximation'.
M. Daoud, J. Douari, Y. Hassouni
Yang-Baxter equation on two-dimensional lattice and some infinite dimensional algebras
Acta Physica Slovaca 49, 945 (1999)
Abstract: We show that the Yang-Baxter equation is equivalent to the associativity of the algebra generated by non-commuting link operators. Starting from these link operators we build out the (FFZ) algebras, the is derived by considering a special combination of the generators of (FFZ) algebra.
A. Grusková, V. Jancárik, J. Sláma
Investigation of phase composition of substituted Mn ferrite
Acta Physica Slovaca 49, 959 (1999)
Abstract: The hematite samples with various content of impurities and its influence on final MnZn ferrite properties were studied. Final MnZn ferrite prepared from hematite with 0.04% SiO impurity contains several ferrite phases. The composition was verified by the temperature dependence of magnetic susceptibility and the magnetization curve measurement. Presence of undesirable phases in hematite and MnZn was proved by the Mössbauer spectroscopy.