Interacting generalized Chaplygin gas
A model with the interaction between generalized Chaplygin gas (GCG) and dark matter is studied. We show that the stationary attractor exists and the universe will enter a de Sitter phase in which the energy densities of both the GCG and dark matter are constant. Because of the interaction between the GCG and the dark matter, the equation of state parameter, w, of the GCG can cross the phantom divide and remains less than −1 once crossed. The larger the GCG model parameter α, the earlier the w crosses the divide and the universe enters the accelerating era, and the larger the present value of w and the present acceleration. By investigating the deceleration parameter, we find that a small α is favored by observations.

title: Emergent universe from the Hořava-Lifshitz gravity

title: Testing Nonstandard Cosmological Models with SNLS3 Supernova Data and Other Cosmological Probes
abstract: We investigate the implications for some nonstandard cosmological models using data from the first three years of the Supernova Legacy Survey (SNLS3), assuming a spatially flat universe. A comparison between the constraints from the SNLS3 and those from other SN Ia samples, such as the ESSENCE, Union2, SDSS-II, and Constitution samples, is given and the effects of different light-curve fitters are considered. We find that analyzing SNe Ia with SALT2 or SALT or SiFTO can give consistent results and the tensions between different data sets and different light-curve fitters are obvious for fewer-free-parameters models. At the same time, we also study the constraints from SNLS3 along with data from the cosmic microwave background and the baryonic acoustic oscillations (CMB/BAO), and the latest Hubble parameter versus redshift (H(z)). Using model selection criteria such as χ2/dof, goodness of fit, Akaike information criterion, and Bayesian information criterion, we find that, among all the cosmological models considered here (ΛCDM, constant w, varying w, Dvali-Gabadadze-Porrati (DGP), modified polytropic Cardassian, and the generalized Chaplygin gas), the flat DGP is favored by SNLS3 alone. However, when additional CMB/BAO or H(z) constraints are included, this is no longer the case, and the flat ΛCDM becomes preferred.

title: Vacuum polarization of scalar electrodynamics in flat space-time with nontrivial topology
abstract: The one-loop vacuum polarization is calculated for scalar electrodynamics in a flat space-time with the topology S1×R3. The effect of vacuum polarization upon photon propagation is considered. It is found that photon propagation becomes anisotropic with some photon modes acquiring a positive topological mass and thus travelling at a subluminal speed.

title: Avoidance of big rip in phantom cosmology by gravitational back reaction
abstract: The effects of the gravitational back reaction of cosmological perturbations are investigated in a cosmological model where the universe is dominated by phantom energy. We assume a COBE normalized spectrum of cosmological fluctuations at the present time and calculate the effective energy–momentum tensor of the gravitational back-reactions of cosmological perturbations whose wavelengths at the time when the back-reactions are evaluated are larger than the Hubble radius. Our results reveal that the effects of gravitational back-reactions will counteract that of phantom energy sooner or later and can become large enough to terminate the phantom dominated phase before the big rip as the universe evolves. This arises because the phase space of infrared modes grows very rapidly as we come close to the big rip.

title: Quantum inequality for negative energy density states of massive Dirac field in four-dimensional spacetime
abstract: Negative energy density and the quantum inequality are examined for the Dirac field. A proof is given of the quantum inequality for negative energy densities in the massive Dirac field produced by the superposition of two single particle electron states.

title: The ASY-EOS experiment at GSI: investigating the symmetry energy at supra-saturation densities
abstract: The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011.