Superintegrable Hamiltonian systems with noncompact invariant submanifolds. Kepler system

The Mishchenko-Fomenko theorem on superintegrable Hamiltonian systems is generalized to superintegrable Hamiltonian systems with noncompact invariant submanifolds. It is formulated in the case of globally superintegrable Hamiltonian systems which admit global generalized action-angle coordinates. The well known Kepler system falls into two different globally superintegrable systems with compact and noncompact invariant submanifolds.Comment: 23 page

Geometrical aspects of integrable systems

We review some basic theorems on integrability of Hamiltonian systems, namely the Liouville-Arnold theorem on complete integrability, the Nekhoroshev theorem on partial integrability and the Mishchenko-Fomenko theorem on noncommutative integrability, and for each of them we give a version suitable for the noncompact case. We give a possible global version of the previous local results, under certain topological hypotheses on the base space. It turns out that locally affine structures arise naturally in this setting.Comment: It will appear on International Journal of Geometric Methods in Modern Physics vol.5 n.3 (May 2008) issu

Flux creep in Bi2Sr2CaCu2O8(sub +x) single crystals

The results of a magnetic study on a Bi2Sr2CaCu2O(8+x) single crystal are reported. Low field susceptibility (dc and ac), magnetization cycles and time dependent measurements were performed. With increasing the temperature the irreversible regime of the magnetization cycles is rapidly restricted to low fields, showing that the critical current J(sub c) becomes strongly field dependent well below T(sub c). At 2.4 K the critical current in zero field, determined from the remanent magnetization by using the Bean formula for the critical state, is J(sub c) = 2 10(exp 5) A/sq cm. The temperature dependence of J(sub c) is satisfactorily described by the phenomenological law J(sub c) = J(sub c) (0) (1 - T/T(sub c) (sup n), with n = 8. The time decay of the zero field cooled magnetization and of the remanent magnetization was studied at different temperatures for different magnetic fields. The time decay was found to be logarithmic in both cases, at least at low temperatures. At T = 4.2 K for a field of 10 kOe applied parallel to the c axis, the average pinning energy, determined by using the flux creep model, is U(sub o) = 0.010 eV

Assessment of Identity Disturbance: Factor Structure and Validation of the Personality Structure Questionnaire in an Italian Sample

here are few brief measures of identity disturbance for use in clinical practice that have been subject to any cross - culturally validation . This study investigated the construct validity of the Personality Structure Questionnaire (PSQ) in Italian clinical (N=237) and community ( N=296) samples . Confirmatory factor analysis was conducted to investigate the internal structure of the PSQ. A three – factor structure (i.e., differing self - states, mood variability and behavioral loss of control) including a second - order factor provided the best fit to the data . This structure was demonstrated to be invariant across sex and clinical diagnosis , with clinical diagnosis significantly predicting increased PSQ scores . A g lobal PSQ score of between 26 - 28 was found to be an appropriate cut-off for assisting in diagnostic processes. Implications for the assessment and treatment of psychological disorders with a marked identity disturbance component are discussed

Global action-angle coordinates for completely integrable systems with noncompact invariant submanifolds

The obstruction to the existence of global action-angle coordinates of Abelian and noncommutative (non-Abelian) completely integrable systems with compact invariant submanifolds has been studied. We extend this analysis to the case of noncompact invariant submanifolds.Comment: 13 pages, to be published in J. Math. Phys. (2007

Exchange bias effect in the phase separated Nd_{1-x}Sr_{x}CoO_3 at the spontaneous ferromagnetic/ferrimagnetic interface

We report the new results of exchange bias effect in Nd_{1-x}Sr_{x}CoO_3 for x = 0.20 and 0.40, where the exchange bias phenomenon is involved with the ferrimagnetic (FI) state in a spontaneously phase separated system. The zero-field cooled magnetization exhibits the FI (T_{FI}) and ferromagnetic (T_C) transitions at ~ 23 and \sim 70 K, respectively for x = 0.20. The negative horizontal and positive vertical shifts of the magnetic hysteresis loops are observed when the system is cooled through T_{FI} in presence of a positive static magnetic field. Training effect is observed for x = 0.20, which could be interpreted by a spin configurational relaxation model. The unidirectional shifts of the hysteresis loops as a function of temperature exhibit the absence of exchange bias above T_{FI} for x = 0.20. The analysis of the cooling field dependence of exchange bias field and magnetization indicates that the ferromagnetic (FM) clusters consist of single magnetic domain with average size around \sim 20 and ~ 40 \AA ~ for x = 0.20 and 0.40, respectively. The sizes of the FM clusters are close to the percolation threshold for x = 0.20, which grow and coalesce to form the bigger size for x = 0.40 resulting in a weak exchange bias effect.Comment: 9 pages, 9 figure

Re-entrant spin glass and magnetoresistance in Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide

We have investigated the static and dynamic response of magnetic clusters in Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide, where a sequence of magnetic phase transitions, i.e., paramagnetic (PM) to ferromagnetic at T_{C} $\leq$ 270K and ferromagnetic to canted spin glass state at T_f$$\leq$ 125K is observed

Laser remote sensing calibration of ocean color satellite data

world ocean: in fact, those processes dramatically affect the climatic equilibrium of our planet. For this reason, many advanced active and passive remote sensors have been used to study phytoplankton dynamics, since such phenomena are thought to be responsible for the sequestration of atmospheric carbon dioxide, one of the most important greenhouse gases. In this paper, one laser system and three satellite radiometers routinely used for the study of the phytoplankton dynamics will be briefly reviewed. Satellite sensors have been preferred to airborne sensors because, to our knowledge, ocean color airborne radiometers have not been operated in Antarctica, at least not throughout the whole lapse of time examined in this study. Particular focus was on the laser system (ELF) and on a specific satellite radiometer (SeaWiFS). ELF is based on the laser-induced fluorescence of phytoplankton pigments and was conceived for the Italian expeditions to Antarctica. The goal of SeaWiFS is to provide the Earth science community with quantitative data on the global ocean bio-optical properties. Such satellite radiometer has been calibrated with in situ data mainly acquired in non polar regions. This is why a comparison between ELF and SeaWiFS measurements of chlorophyll-a surface concentrations in the Southern Ocean during the austral summer 1997-1998 was believed to be significant. Our results indicate that SeaWiFS overestimates high concentrations and underestimates low concentrations. In order to correct this behavior, the chlorophyll- a bio-optical algorithm of SeaWiFS has been recalibrated according to the measurements of ELF, thus providing a new estimation of the primary production in the Southern Ocean

Magnetic properties of the frustrated AFM spinel ZnCr_2O_4 and the spin-glass Zn_{1-x}Cd_xCr_2O_4 (x=0.05,0.10)

The $T$-dependence (2- 400 K) of the electron paramagnetic resonance (EPR), magnetic susceptibility, $\chi (T)$, and specific heat, $C_{v}(T)$, of the $normal$ antiferromagnetic (AFM) spinel ZnCr$_{2}$O$_{4}$ and the spin-glass (SG) Zn$_{1-x}$Cd$_{x}$Cr$_{2}$O$_{4}$ ($x=0.05,0.10$) is reported. These systems behave as a strongly frustrated AFM and SG with $$ $\approx T_{G}\approx 12$ K and -400 K $\gtrsim \Theta_{CW}\gtrsim -500$ K. At high-$T$ the EPR intensity follows the $\chi (T)$ and the $g$-value is $T$-independent. The linewidth broadens as the temperature is lowered, suggesting the existence of short range AFM correlations in the paramagnetic phase. For ZnCr$_{2}$O$_{4}$ the EPR intensity and $\chi (T)$ decreases below 90 K and 50 K, respectively. These results are discussed in terms of nearest-neighbor Cr$^{3+}$ (S $=3/2$%) spin-coupled pairs with an exchange coupling of $| J/k| \approx$ 50 K. The appearance of small resonance modes for $T\lesssim 17$ K, the observation of a sharp drop in $\chi (T)$ and a strong peak in $C_{v}(T)$ at $T_{N}=12$ K confirms, as previously reported, the existence of long range AFM correlations in the low-$T$ phase. A comparison with recent neutron diffraction experiments that found a near dispersionless excitation at 4.5 meV for $T\lesssim T_{N}$ and a continuous gapless spectrum for $T\gtrsim T_{N}$, is also given.Comment: 17 pages, 8 figures, 1 Table. Submitted to Physical Review