85,719 research outputs found
Evidence of spin liquid with hard-core bosons in a square lattice
We show that laser assisted hopping of hard core bosons in a square optical
lattice can be described by an antiferromagnetic - XY model with
tunable ratio of . We numerically investigate the phase diagram of
the - XY model using both the tensor network algorithm for
infinite systems and the exact diagonalization for small clusters and find
strong evidence that in the intermediate region around ,
there is a spin liquid phase with vanishing magnetization and valence bond
orders, which interconnects the Neel state on the side and the
stripe antiferromagnetic phase on the side. This finding
opens up the possibility of studying the exotic spin liquid phase in a
realistic experimental system using ultracold atoms in an optical lattice.Comment: 5 pages, 5 figure
Effects of f(R) Model on the Dynamical Instability of Expansionfree Gravitational Collapse
Dark energy models based on f(R) theory have been extensively studied in
literature to realize the late time acceleration. In this paper, we have chosen
a viable f(R) model and discussed its effects on the dynamical instability of
expansionfree fluid evolution generating a central vacuum cavity. For this
purpose, contracted Bianchi identities are obtained for both the usual matter
as well as dark source. The term dark source is named to the higher order
curvature corrections arising from f(R) gravity. The perturbation scheme is
applied and different terms belonging to Newtonian and post Newtonian regimes
are identified. It is found that instability range of expansionfree fluid on
external boundary as well as on internal vacuum cavity is independent of
adiabatic index but depends upon the density profile, pressure
anisotropy and f(R) model.Comment: 26 pages, no figure. arXiv admin note: text overlap with
arXiv:1108.266
A Large Eddy Simulation of Turbulent Compressible Convection: Differential Rotation in the Solar Convection Zone
We present results of two simulations of the convection zone, obtained by
solving the full hydrodynamic equations in a section of a spherical shell. The
first simulation has cylindrical rotation contours (parallel to the rotation
axis) and a strong meridional circulation, which traverses the entire depth.
The second simulation has isorotation contours about mid-way between cylinders
and cones, and a weak meridional circulation, concentrated in the uppermost
part of the shell.
We show that the solar differential rotation is directly related to a
latitudinal entropy gradient, which pervades into the deep layers of the
convection zone. We also offer an explanation of the angular velocity shear
found at low latitudes near the top. A non-zero correlation between radial and
zonal velocity fluctuations produces a significant Reynolds stress in that
region. This constitutes a net transport of angular momentum inwards, which
causes a slight modification of the overall structure of the differential
rotation near the top. In essence, the {\it thermodynamics controls the
dynamics through the Taylor-Proudman momentum balance}. The Reynolds stresses
only become significant in the surface layers, where they generate a weak
meridional circulation and an angular velocity `bump'.Comment: 11 pages, 14 figures, the first figure was too large and is excluded.
Accepted for publication in MNRA
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