Band splitting and relative spin alignment in bilayer systems

Influence of relative spin alignment on the band splitting and magnetic excitations in the bilayer correlated systems is studied. Splitting occures to be large or small depending on orientation of staggered spins of layers. Change of the ground state configuration with doping is shown. Behavior of the bilayer splitting in Bi-based cuprate allows to suppose that superconducting transition is accompanied by transformation of spin configuration of system.Comment: 9 pages, 3 figure

Multiphonon anharmonic decay of a quantum mode

A nonperturbative theory of multiphonon anharmonic transitions between energy levels of a local mode is presented. It is shown that the rate of transitions rearranges near the critical level number $n_{cr}$: at smaller $n$ the process slows down, while at larger $n$ it accelerates in time, causing a jump-like loss of energy followed by the generation of phonon bursts. Depending on parameters, phonons are emitted in pairs, triplets etc.Comment: submitted to Europhys.Let

Massive liquid Ar and Xe detectors for direct Dark Matter searches

A novel experiment for direct searches of the Dark Matter with liquid argon double-phase chamber with a mass of liquid Ar up to several hundred tons is proposed. To suppress the b-, g- and n0- backgrounds, the comparison of scintillation and ionization signals for every event is suggested. The addition in liquid Ar of photosensitive Ge(CH3)4 or C2H4 and suppression of triplet component of scintillation signals ensures the detection of scintillation signals with high efficiency and provides a complete suppression of the electron background. For the detection of photoelectrons and ionization electrons, highly stable and reliable GEM detectors must be used.Comment: 8 pages, 2 figures, 1 tabl

Research, development and application of the innovational technology of high quality pump-compressor pipes production from sections

The innovational technology of high-strength, cold- and corrosion-resistant pump-compressor pipes from sections was developed. It includes the reduction process inside three-high stand of screw rolling before piercing in the «80» pipe-rolling mill line in OAO SinTZ. The special attention is paid to the questions of fine-grained steel production and final tubes quality. It is shown that new technology is efficient from the point of tube production of high level mechanical properties

Influence of spin structures and nesting on Fermi surface and a pseudogap anisotropy in t-t'-U Hubbard model

Influence of two type of spin structures on the form of the Fermi surface (FS) and a photoemission intensity map is studied for t-t'-U Hubbard model. Mean field calculations are done for the stripe phase and for the spiral spin structure. It is shown, that unlike a case of electron doping, the hole-doped models are unstable with respect to formation of such structures. The pseudogap anisotropies are different for h- and e- doping. In accordance with ARPES data for La2SrxCuO4 the stripe phase is characterized by quasi-one-dimensional segments of FS at k=(\pi,0) and by suppression of spectral weight in diagonal direction. It is shown that spiral structures display the polarisation anisotropy: different segments of FS correspond to electros with different spin polarisations.Comment: 12 pages, 4 figure

Semileptonic decays of pseudoscalar mesons to scalar "f_0" meson

The transition form factors of (D_s -> f_0 l nu), (D -> f_0 l nu) and (B_u -> f_0 l nu) decays are calculated in 3-point QCD sum rule method, assuming that "f_0" is a quark-antiquark state with a mixture of strange and light quarks. The branching ratios of these decays are calculated in terms of the mixing angle.Comment: 12 pages, 4 figures, LaTeX formatte