Quantum-classical transition in the Caldeira-Leggett model

The quantum-classical transition in the Caldeira-Leggett model is investigated in the framework of the functional renormalization group method. It is shown that a divergent quadratic term arises in the action due to the heat bath in the model. By removing the divergence with a frequency cutoff we considered the critical behavior of the model. The critical exponents belonging to the susceptibility and the correlation length are determined and their independence of the frequency cutoff and the renormalization scheme is shown.Comment: 8 pages, 4 figure

DESIGN PROBLEMS OF TRANSFORM CODERS FOR IMAGE TRANSMISSION

Some experiments have been undertaken with general coder circuit models. These experiments revealed the possibility that coders implemented by the use of adders only, are suitable for coding video signals in real-time operation. During the experiments the authors applied relatively small N values, which is not always advantageous for transform efficiency. The applied components were of TTL-S and ECL-types. The parallel processing described in short in point 4, provides the possibility to code simultaneously a larger image section (N above 4). In this way the development of VLSI integrated circuit, specially designed for transform coding purposes can be achieved. This type of development is being undertaken in several parts of the world

The electronic structure and the phases of BaVS3

BaVS3 is a moderately correlated d-electron system with a rich phase diagram. To construct the corresponding minimal electronic model, one has to decide which d-states are occupied, and to which extent. The ARPES experiment presented here shows that the behavior of BaVS3 is governed by the coexistence of wide-band (A_1g) and narrow-band (twofold degenerate E) d-electrons. We sketch a lattice fermion model which may serve as a minimal model of BaVS3. This serves foremost for the understanding of the metal-insulator in pure BaVS3 and its absence in some related compounds. The nature of the low temperature magnetic order differs for several systems which may be described in terms of the same electron model. We describe several recent experiments which give information about magnetic order at high pressures. In particular, we discuss field-induced insulator-to-metal transition at slightly subcritical pressures, and an evidence for magnetic order in the high-pressure metallic phase. The phase diagram of Sr-doped BaVS3 is also discussed. The complexity of the phases of BaVS3 arises from the fact that it is simultaneously unstable against several kinds of instabilities.Comment: Presented at the International Conference on Magnetism 2006 (Kyoto), 6 pages, 9 figure

Shot Noise Probing of Magnetic Ordering in Zigzag Graphene Nanoribbons

The nonequilibrium time-dependent fluctuations of charge current have recently emerged as a sensitive experimental tool to probe ballistic transport through evanescent wave functions introduced into clean wide and short graphene strips by the attached metallic electrodes. We demonstrate that such "pseudo-diffusive" shot noise can be substantially modified in zigzag graphene nanoribbon (ZGNR) due to the topology of its edges responsible for localized states that facilitate ferromagnetic ordering along the edge when Coulomb interaction is taken into account. Thus, the shot noise enhancement of unpolarized, and even more sensitively of spin-polarized, charge currents injected into ZGNR will act as an all-electrical and edge-sensitive probe of such low-dimensional magnetism.Comment: 5 pages, 3 color figures; references update

Orbital degeneracy as a source of frustration in LiNiO2_2

Motivated by the absence of cooperative Jahn-Teller effect and of magnetic ordering in LiNiO$_2$, a layered oxide with triangular planes, we study a general spin-orbital model on the triangular lattice. A mean-field approach reveals the presence of several singlet phases between the SU(4) symmetric point and a ferromagnetic phase, a conclusion supported by exact diagonalizations of finite clusters. We argue that one of the phases, characterized by a large number of low-lying singlets associated to dimer coverings of the triangular lattice, could explain the properties of LiNiO$_2$, while a ferro-orbital phase that lies nearby in parameter space leads to a new prediction for the magnetic properties of NaNiO$_2$.Comment: 18 pages, 17 figure

Orbital order and spin-orbit coupling in BaVS3

The correlated 3d sulphide BaVS3 undergoes a sequence of three symmetry breaking transitions which are reflected in the temperature dependence of the magnetic susceptibility, and its anisotropy. We introduce a microscopic model based on the coexistence of wide band a(1g) and localized e(g) d-electrons, and give the classification of the order parameters under the double space group and time reversal symmetries. Allowing for the relativistic spin-orbit coupling, the d-shell multipoles acquire a mixed spin-orbital character. It follows that orbital ordering is accompanied by a change in the susceptibility anisotropyComment: 2 pages, submitted to the SCES05 conference, uses elsart41.cl

Motion Compensated Video Compression with 3D Wavelet Transform and SPIHT

The following paper introduces a low bitrate video coding method on the basis of 3D motion compensated wavelet transform and SPIHT algorithm. In contrast to the conventional algorithms applying motion compensation and differential coding, here wavelet transform is used to exploit the opportunities of time redundancy. For coefficient collection, the 3D version of SPIHT algorithm was selected from the various procedures developed for wavelet transform. Motion vectors are compressed, too (also by wavelet transform), therefore the time and spatial redundancy of coding is exploited here as well. These procedures result in effective video compressing and can easily be aligned to the MPEG4 standard