11,313 research outputs found
Magnetism of Cold Fermionic Atoms on p-Band of an Optical Lattice
We carry out \textit{ab initio} study of ground state phase diagram of
spin-1/2 cold fermionic atoms within two-fold degenerate -band of an
anisotropic optical lattice. Using the Gutzwiller variational approach, we show
that a robust ferromagnetic phase exists for a vast range of band fillings and
interacting strengths. The ground state crosses over from spin density wave
state to spin-1 Neel state at half filling. Additional harmonic trap will
induce spatial separation of varies phases. We also discuss several relevant
observable consequences and detection methods. Experimental test of the results
reported here may shed some light on the long-standing issue of itinerant
ferromagnetism.Comment: 5 pages, 4 figure
Screening of point charge impurities in highly anisotropic metals: application to spin relaxation in underdoped cuprates
We calculate the screening charge density distribution due to a point charge,
such as that of a positive muon (), placed between the planes of a
highly anisotropic layered metal. In underdoped hole cuprates the screening
charge converts the charge density in the metallic-plane unit cells in the
vicinity of the to nearly its value in the insulating state. The
current-loop ordered state observed by polarized neutron diffraction then
vanishes in such cells, and also in nearby cells over a distance of order the
intrinsic correlation length of the loop-ordered state. This in turn strongly
suppresses the loop-current field at the site. We estimate this
suppressed field in underdoped YBaCuO and
LaSrCuO, and find consistency with the observed 0.2--0.3 G
field in the former case and the observed upper bound of 0.2 G in the
latter case. This resolves the controversy between the neutron diffraction and
SR experiments. The screening calculation also has relevance for the
effect of other charge impurities in the cuprates, such as the dopants
themselves
Application of Generalised Differential Quadrature to Solve Two-Dimensional Incompressible Navier-Stokes Equations. G.U. Aero Report 9227
A global method of generalized differential quadrature is applied to solve the two-dimensional incompressible Navier-Stokes equations in the vorticity-stream function formulation. Numerical results for the flow past a circular cylinder were obtained using just a few grid points. Good agreements are achieved, compared with the experimental
data
U(1) symmetry and elimination of spin-0 gravitons in Horava-Lifshitz gravity without the projectability condition
In this paper, we show that the spin-0 gravitons appearing in Horava-Lifshitz
gravity without the projectability condition can be eliminated by extending the
gauge symmetries of the foliation-preserving diffeomorphisms to include a local
U(1) symmetry. As a result, the problems of stability, ghost, strong coupling,
and different speeds in the gravitational sector are automatically resolved. In
addition, with the detailed balance condition softly breaking, the number of
independent coupling constants can be significantly reduced (from more than 70
down to 15), while the theory is still UV complete and possesses a healthy IR
limit, whereby the prediction powers of the theory are considerably improved.
The strong coupling problem in the matter sector can be cured by introducing an
energy scale , so that , where denotes
the suppression energy of high order derivative terms, and
the would-be strong coupling energy scale.Comment: Revtex4, no figures. Some typos are corrected. Phys. Rev. D84, 101502
(R) (2011
Measurement of Lande g factor of 5D5/2 state of BaII with a single trapped ion
We present the first terrestrial measurement of the Lande g factor of the
5D5/2 state of singly ionized barium. Measurements were performed on single
Doppler-cooled 138Ba+ ions in a linear Paul trap. A frequency-stabilized fiber
laser with nominal wavelength 1.762 um was scanned across the 6S1/25D5/2
transition to spectroscopically resolve transitions between Zeeman sublevels of
the ground and excited states. From the relative positions of the four narrow
transitions observed at several different values for the applied magnetic
field, we find a value of 1.2020+/-0.0005 for g of 5D5/2.Comment: 3 figure
Realistic Magnetohydrodynamical Simulation of Solar Local Supergranulation
Three-dimensional numerical simulations of solar surface magnetoconvection
using realistic model physics are conducted. The thermal structure of
convective motions into the upper radiative layers of the photosphere, the main
scales of convective cells and the penetration depths of convection are
investigated. We take part of the solar photosphere with size of 60x60 Mm in
horizontal direction and by depth 20 Mm from level of the visible solar
surface. We use a realistic initial model of the Sun and apply equation of
state and opacities of stellar matter. The equations of fully compressible
radiation magnetohydrodynamics with dynamical viscosity and gravity are solved.
We apply: 1) conservative TVD difference scheme for the magnetohydrodynamics,
2) the diffusion approximation for the radiative transfer, 3) dynamical
viscosity from subgrid scale modeling. In simulation we take uniform
two-dimesional grid in gorizontal plane and nonuniform grid in vertical
direction with number of cells 600x600x204. We use 512 processors with
distributed memory multiprocessors on supercomputer MVS-100k in the Joint
Computational Centre of the Russian Academy of Sciences.Comment: 6 pages, 5 figures, submitted to the proceedings of the GONG 2008 /
SOHO XXI conferenc
A Coronal Hole's Effects on CME Shock Morphology in the Inner Heliosphere
We use STEREO imagery to study the morphology of a shock driven by a fast
coronal mass ejection (CME) launched from the Sun on 2011 March 7. The source
region of the CME is located just to the east of a coronal hole. The CME ejecta
is deflected away from the hole, in contrast with the shock, which readily
expands into the fast outflow from the coronal hole. The result is a CME with
ejecta not well centered within the shock surrounding it. The shock shape
inferred from the imaging is compared with in situ data at 1 AU, where the
shock is observed near Earth by the Wind spacecraft, and at STEREO-A. Shock
normals computed from the in situ data are consistent with the shock morphology
inferred from imaging.Comment: to appear in The Astrophysical Journa
Probing the Slope of Cluster Mass Profile with Gravitational Einstein Rings: Application to Abell 1689
The strong lensing modelling of gravitational ``rings'' formed around massive
galaxies is sensitive to the amplitude of the external shear and convergence
produced by nearby mass condensations. In current wide field surveys, it is now
possible to find out a large number of rings, typically 10 gravitational rings
per square degree. We propose here, to systematically study gravitational rings
around galaxy clusters to probe the cluster mass profile beyond the cluster
strong lensing regions. For cluster of galaxies with multiple arc systems, we
show that rings found at various distances from the cluster centre can improve
the modelling by constraining the slope of the cluster mass profile. We outline
the principle of the method with simple numerical simulations and we apply it
to 3 rings discovered recently in Abell~1689. In particular, the lens modelling
of the 3 rings confirms that the cluster is bimodal, and favours a slope of the
mass profile steeper than isothermal at a cluster radius \sim 300 \kpc. These
results are compared with previous lens modelling of Abell~1689 including weak
lensing analysis. Because of the difficulty arising from the complex mass
distribution in Abell~1689, we argue that the ring method will be better
implemented on simpler and relaxed clusters.Comment: Accepted for publication in MNRAS. Substantial modification after
referee's repor
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