240 research outputs found
Dark Energy in Global Brane Universe
We discuss the exact solutions of brane universes and the results indicate
the Friedmann equations on the branes are modified with a new density term.
Then, we assume the new term as the density of dark energy. Using Wetterich's
parametrization equation of state (EOS) of dark energy, we obtain the new term
varies with the red-shift z. Finally, the evolutions of the mass density
parameter , dark energy density parameter and deceleration
parameter q_2 are studied.Comment: 8 pages,4 figure
Statefinder Parameters for Five-Dimensional Cosmology
We study the statefinder parameter in the five-dimensional big bounce model,
and apply it to differentiate the attractor solutions of quintessence and
phantom field. It is found that the evolving trajectories of these two
attractor solutions in the statefinder parameters plane are quite different,
and that are different from the statefinder trajectories of other dark energy
models.Comment: 8 pages, 12 figures. accepted by MPL
Genuine Dirac half-metal: A 2D d0-type ferromagnet Mg4N4
When the spin-orbit coupling (SOC) is absent, almost all the proposed
half-metals with the twofold degenerate nodal points at the K (or K') in
two-dimensional (2D) materials are misclassified as "Dirac half-metals" owing
to the way graphene was utilized in the earliest studies. Actually, each band
crossing point at K or K' is described by a 2D Weyl Hamiltonian with definite
chirality; hence, it must be a Weyl point. To the best of our knowledge, there
have been no reports of a genuine (i.e., fourfold degenerate) Dirac point
half-metal in 2D yet. In this Letter, we proposed for the first time that the
2D d0-type ferromagnet Mg4N4 is a genuine Dirac half-metal with a fourfold
degenerate Dirac point at the S high-symmetry point, intrinsic magnetism, high
Curie temperature, 100% spin-polarization, robustness to the SOC and uniaxial
and biaxial strains, and 100% spin-polarized edge states. The work can be seen
as a starting point for future predictions of intrinsically magnetic materials
with genuine Dirac points, which will aid the frontier of topo-spintronics
researchers
Statefinder Parameters for Interacting Phantom Energy with Dark Matter
We apply in this paper the statefinder parameters to the interacting phantom
energy with dark matter. There are two kinds of scaling solutions in this
model. It is found that the evolving trajectories of these two scaling
solutions in the statefinder parameter plane are quite different, and that are
also different from the statefinder diagnostic of other dark energy models.Comment: 9 pages, 12 figures, some references are added, some words are
modifie
Reconstruction of 5D Cosmological Model From Recent Observations
We use a parameterized equation of state (EOS) of dark energy to a 5D
Ricci-flat cosmological solution and suppose the universe contains two major
components: dark matter and dark energy. Using the recent observational
datasets: the latest 182 type Ia Supernovae Gold data, the 3-year WMAP CMB
shift parameter and the SDSS baryon acoustic peak, we obtain the best fit
values of the EOS and two major components' evolution. We find that the best
fit EOS crossing -1 in the near past , the present best fit value
of and for this model the universe experiences the acceleration at
about .Comment: 7 pages, 3 figs, Accept by IJMP
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