Measurement and analysis of reversible transformations of vortex-free and singular light fields produced by PDLC cells

In this work, we have firstly realized and investigated reversible transformations of vortex-free and singular optical complex landscapes appearing in a He-Ne laser beam transmitted through a PDLC cell, which is controlled by an applied DC voltage. Biaxes of all micro size LC domains are oriented approximately along the applied electric field, and vortex-free complex landscape exists at 200 V. At 160 V, biaxes orientation spreads, and the first ‘embryo’ of vortices in the form of a smooth phase step appears. The first vortex pair nucleates at 140 V. Multitude of vortex pairs is realized when electric field is switched off. Reversed evolution is realized when the applied DC voltage grows from zero value to 200 V. It was shown that the observed topological evolution is fully defined by changes in structure and localization of real and imaginary zero-intensity lines for output complex light field. The developed technique of parametric dynamics can be applied successfully to realize and investigate various types of controlled optical elements including media with nanoadditions

Recent advances in neutrinoless double beta decay search

Even after the discovery of neutrino flavour oscillations, based on data from atmospheric, solar, reactor, and accelerator experiments, many characteristics of the neutrino remain unknown. Only the neutrino square-mass differences and the mixing angle values have been estimated, while the value of each mass eigenstate still hasn't. Its nature (massive Majorana or Dirac particle) is still escaping. Neutrinoless double beta decay ($0\nu$-DBD) experimental discovery could be the ultimate answer to some delicate questions of elementary particle and nuclear physics. The Majorana description of neutrinos allows the $0\nu$-DBD process, and consequently either a mass value could be measured or the existence of physics beyond the standard should be confirmed without any doubt. As expected, the $0\nu$-DBD measurement is a very difficult field of application for experimentalists. In this paper, after a short summary of the latest results in neutrino physics, the experimental status, the R&D projects, and perspectives in $0\nu$-DBD sector are reviewed.Comment: 36 pages, 7 figures, To be publish in Czech Journal of Physic

The magnetic ordering in the mixed valence compound beta-Na0.33V2O5

The low-temperature electron spin resonance (ESR) spectra and the static magnetization data obtained for the stoichiometric single crystals of $\beta$-Na$_{0.33}$V$_2$O$_5$ indicate that this quasi-one-dimensional mixed valence (V4+/V5+) compound demonstrates at $T_N=22$ K the phase transition into the canted antiferromagnetically ordered state. The spontaneous magnetization of $3.4\times 10^{-3}$ $\mu_B$ per V$^{4+}$ ion was found to be oriented along the two-fold $b$ axis of the monoclinic structure, the vector of antiferromagnetism is aligned with the $a$ axis and the Dzyaloshinsky vector is parallel to the $c$-axis. The experimental data were successfully described in the frame of the macroscopic spin dynamics and the following values for the macroscopic parameters of the spin system were obtained: the Dzyaloshinsky field $H_D=6$ kOe, the energy gaps of two branches of the spin wave spectrum $\Delta_1=48$ GHz and $\Delta_2=24$ GHz.Comment: 5 pages, 6 figure