[en] Short communication

[en] Inspired by the increasing possibility of experimental control in ultracold atomic physics we introduce a new Lax operator and use it to construct and solve models with two wells and two on well states together with its generalization for n on well states. The models are solved by the algebraic Bethe Ansatz method and can be viewed as describing two Bose-Einstein condensates allowing for an exchange interaction through Josephson tunneling. (author)

[en] We will start with a short description of the general thermodynamic approach to plasmas with multiple ionization (section II). In Section III and IV we give a survey of formulae recently developed for the thermodynamic functions. Then we continue with some applications to xenon and to helium plasmas (section V and VI). Special attention will be paid to the plasma phase transitions. Some of the results summarized here have been obtained in collaboration with T. Kahlbaum. (orig.)

No abstract available

[en] The production of K⁺ and of K^- mesons in heavy-ion collisions at beam energies of 1 to 2 A GeV has systematically been investigated with the kaon spectrometer KaoS. The ratio of the K⁺ production excitation function for Au+Au and for C+C reactions increases with decreasing beam energy, which is expected for a soft nuclear equation-of-state. A comprehensive study of the K⁺ and of the K^- emission as a function of the size of the collision system, of the collision centrality, of the kaon energy, and of the polar emission angle has been performed. The K^-/K⁺ ratio is found to be nearly constant as a function of the collision centrality and can be explained by the dominance of strangeness exchange. On the other hand, the spectral slopes and the polar emission patterns are different for K^- and for K⁺. Furthermore the azimuthal distribution of the particle emission has been investigated. K⁺ mesons and pions are emitted preferentially perpendicular to the reaction plane as well in Au+Au as in Ni+Ni collisions. In contrast for K^- mesons in Ni+Ni reactions an in-plane flow was observed for the first time at these incident energies

[en] We investigate the algebraic structure of the supersymmetric t-J model in one dimension. We prove that the Bethe ansatz states are highest weight vectors of an spl(2,1) superalgebra. By acting with shift operators we construct a complete set of states for this model. In addition we analyse the multiplet structure of the anti-ferromagnetic ground state and some low lying excitations. It turns out that the ground state is a member of a quartet. (orig.)

[en] Infrared absorption bands due to the fundamental and the overtone of OH and OD stretch modes are investigated in undoped, Mg-doped, and benzoic acid treated LiNbO₃. The different bands are interpreted using an anharmonic oscillator model. Spectroscopic parameters determined from the isotope shift and the overtone frequencies are in good agreement. The anharmonicity found is comparable to that of OH in other ABO₃ compounds and in alkali halides. (author)

[en] New challenging technologies based upon laser and particle beams, plasma light sources, X-ray lasers, and controlled fusion, the arc physics and astrophysical research focus theoretical investigations and applied research on strongly coupled plasmas. The book provides new results on the plasma composition, the equation of state and other thermodynamic properties for plasmas with higher charges and for mixed plasmas. Using different theoretical models also energy level shifts, ionization and recombination kinetics, electrical and thermal conductivity, light absorption and plasma stopping power are discussed. Besides a review of the theory, useful semiempirical formulae are derived. Tables of thermophysical properties of plasmas which are especially relevant for practical applications close the book. (orig.)

[en] The one-component plasma (OCP), an electron gas on a positive background, and the subsystem of free charges in a two-component plasma (TCP) is investigated using a quasi-classical approach. Quantum effects such as the Heisenberg uncertainty principle and the Pauli exclusion principle are incorporated into our model by effective potentials. In case of the OCP the symmetry effects are of special interest whereas in case of TCP the Heisenberg effects play the significant role. The method of Slater sums is used to obtain effective potentials. Monte Carlo simulations for both OCP and TCP were carried out to calculate the Coulombic energy, the effective energy, and the pair-distribution functions. (orig.)

[en] We introduce an integrable model for two coupled BCS systems through a solution of the Yang-Baxter equation associated with the Lie algebra su(4). By employing the algebraic Bethe Ansatz, we determine the exact solution for the energy spectrum. An asymptotic analysis is conducted to determine the leading terms in the ground state energy, the gap and some one point correlation functions at zero temperature