acta physica slovaca

Abstract: We study a system of large number of singly quantized vortices in a rotating Bose-Einstein condensate. Analogous to the Meissner effect in superconductors, we show that the vector potential due to the external rotational field can be tuned to cancel the vector potential due to the Magnus field, resulting in a zero average angular momentum and a zero shear modulus of the vortex lattice. The vortex lattice state exhibits two states, namely, an elastic state and a plastic state. A clear distinction between these states is controlled by the filling fraction nu=N/Nv, which is the ratio of the number of bosons (N) to the average number of vortices Nv.

Abstract: After a brief review of the different types of quaternions, we express the special Galilean space-time transformation in an algebraic ring of the exotic four-component numbers forming the system of dual quaternions.

Abstract: We present our calculations of energy levels for two, three and four inductively coupled flux qubits. In order to measure this system, qubits are weakly coupled to a high-quality tank circuit. Measurements of the current-voltage phase shift vs. external flux for two qubits using impedance measurement technique have been carried out. Our experimental data are in very good agreement with the calculated theoretical curves. By calculating the tangent of the current-voltage phase shift for four inductively coupled flux qubits we have predicted behavior of these systems, that is needed for future measurements because of their high complexity.

Abstract: We present preliminary results for identified hadrons (pi^{+-}, K^{+-} and p^{+-}) measured from Au+Au collisions at (s_NN)^0.5 = 62.4 GeV in BRAHMS experiment at RHIC. The results coming out of the collisions at this energy are an important consistency check between the lower energies (AGS, SPS) and RHIC full energies. Here we investigate the p_T and rapidity dependence of the anti-particle to particle ratios and also of the strangeness ratios K^{+-} / pi^{+-}. A comparison with the predictions of the statistical model is also made.

Abstract: The momentum integrated Boltzmann equation has been used to study the evolution of strangeness of the strongly interacting system formed after the heavy ion collisions at relativistic energies.We argue that the experimentally observed non-monotonic, horn-like structure in the variation of the K^+ / pi^+$ with colliding energy appears due to the release of large number of colour degrees of freedom.

Abstract: We present an NMR study of hyperfine fields at 57Fe nuclei in polycrystalline yttrium iron garnet. We measured spectra of 57Fe nuclei situated in tetrahedral and octahedral sites in magnetic domains as well as in domain walls at several temperatures within the range of 4.2 -- 344 K. Comparing the simulated lineshapes to the experimental ones we found that the main contribution to the observed spectra from walls originated from nuclei in 70.5 degrees Bloch walls.

Abstract: High-Tc superconducting thin films based on thallium were prepared by a two step method combining RF magnetron sputtering and ex-situ thallination. We studied the influence of rhenium on the properties of the precursor and final superconducting films. Precursors of the Re_0.25 Ba_2 Ca_2 Cu_3 O_x composition with a thickness of 300 nm were deposited on top of a CeO_2 buffered R-plane sapphire. Thallination was performed at 830 -- 870 C. Rhenium avoids air contamination of the target used for sputtering we observed that it has no influence on the superconducting properties. X-ray analysis showed that the prepared films were Tl_2 Ba_2 Ca Cu _2 O_x phase with the c-axis growth orientation. The films had a zero resistance below 100 K.