[en] We apply the statefinder diagnostic to the modified polytropic Cardassian universe in this work. We find that the statefinder diagnostic is quite effective to distinguish Cardassian models from a series of other cosmological models. The s-r plane is used to classify the modified polytropic Cardassian models into six cases. The evolutionary trajectories in the s-r plane for the cases with different n and β reveal different evolutionary properties of the universe. In addition, we combine the observational H(z) data, the cosmic microwave background data, and the baryonic acoustic oscillation data to make a joint analysis. We find that case 2 can be excluded at the 68.3% confidence level and any case is consistent with the observations at the 95.4% confidence level

[en] We present a theoretical study of spin transport in a series of organometallic iron-cyclopentadienyl, Fe_nCp_n+1, multidecker clusters sandwiched between either gold or platinum electrodes. Ab initio modeling is performed by combining the non-equilibrium Green's function formalism with spin density functional theory. Due to the intrinsic bonding nature, the low-bias conductance of the Fe_nCp_n+1 clusters contacted to gold electrodes is relatively small even for strong cluster-electrode coupling. However, a nearly 100% spin polarization of the transmitted electrons can be achieved for the Fe_nCp_n+1 (n>2) clusters. In contrast, the Fe_nCp_n+1 (n>2) clusters attached to platinum electrodes through Pt adatoms not only can act as nearly perfect spin filters but also show a much larger transmission around the Fermi level, demonstrating their promising applications in future molecular spintronics.

[en] In this work, we use observations of the Hubble parameter from the differential ages of passively evolving galaxies and the recent detection of the Baryon Acoustic Oscillations (BAO) at z₁=0.35 to constrain the Dvali-Gabadadze-Porrati (DGP) Universe. For the case with a curvature term, we set a prior h=0.73+/-0.03 and the best-fit values suggest a spatially closed Universe. For a flat Universe, we set h free and we get consistent results with other recent analyses

[en] The thermodynamical properties of dark energy are usually investigated with the equation of state ω=ω₀+ω₁z. Recent observations show that our Universe is accelerating, and the apparent horizon and the event horizon vary with redshift z. Because definitions of the temperature and entropy of a black hole are used to describe the two horizons of the Universe, we examine the thermodynamical properties of the Universe, which is enveloped by the apparent horizon and the event horizon, respectively. We show that the first and the second laws of thermodynamics inside the apparent horizon in any redshift are satisfied, while they are broken down inside the event horizon in some redshifts. Therefore, the apparent horizon for the Universe may be the boundary of thermodynamical equilibrium for the Universe like the event horizon for a black hole