24,955 research outputs found
Geometric entanglement from matrix product state representations
An efficient scheme to compute the geometric entanglement per lattice site
for quantum many-body systems on a periodic finite-size chain is proposed in
the context of a tensor network algorithm based on the matrix product state
representations. It is systematically tested for three prototypical critical
quantum spin chains, which belong to the same Ising universality class. The
simulation results lend strong support to the previous claim [Q.-Q. Shi, R.
Or\'{u}s, J. O. Fj{\ae}restad, and H.-Q. Zhou, New J. Phys \textbf{12}, 025008
(2010); J.-M. St\'{e}phan, G. Misguich, and F. Alet, Phys. Rev. B \textbf{82},
180406R (2010)] that the leading finite-size correction to the geometric
entanglement per lattice site is universal, with its remarkable connection to
the celebrated Affleck-Ludwig boundary entropy corresponding to a conformally
invariant boundary condition.Comment: 4+ pages, 3 figure
Morphological evolution of a 3D CME cloud reconstructed from three viewpoints
The propagation properties of coronal mass ejections (CMEs) are crucial to
predict its geomagnetic effect. A newly developed three dimensional (3D) mask
fitting reconstruction method using coronagraph images from three viewpoints
has been described and applied to the CME ejected on August 7, 2010. The CME's
3D localisation, real shape and morphological evolution are presented. Due to
its interaction with the ambient solar wind, the morphology of this CME changed
significantly in the early phase of evolution. Two hours after its initiation,
it was expanding almost self-similarly. CME's 3D localisation is quite helpful
to link remote sensing observations to in situ measurements. The investigated
CME was propagating to Venus with its flank just touching STEREO B. Its
corresponding ICME in the interplanetary space shows a possible signature of a
magnetic cloud with a preceding shock in VEX observations, while from STEREO B
only a shock is observed. We have calculated three principle axes for the
reconstructed 3D CME cloud. The orientation of the major axis is in general
consistent with the orientation of a filament (polarity inversion line)
observed by SDO/AIA and SDO/HMI. The flux rope axis derived by the MVA analysis
from VEX indicates a radial-directed axis orientation. It might be that locally
only the leg of the flux rope passed through VEX. The height and speed profiles
from the Sun to Venus are obtained. We find that the CME speed possibly had
been adjusted to the speed of the ambient solar wind flow after leaving COR2
field of view and before arriving Venus. A southward deflection of the CME from
the source region is found from the trajectory of the CME geometric center. We
attribute it to the influence of the coronal hole where the fast solar wind
emanated from.Comment: ApJ, accepte
Study of Decays in the Family Non-universal Models
In a combined investigation of the decays,
constraints on the related couplings in family non-universal
models are derived. We find that within the allowed parameter space, the
recently observed forward-backward asymmetry in the
decay can be explained, by flipping the signs of the Wilson coefficients
and . With the obtained constraints, we also calculate
the branching ratio of the decay. The upper bound of our
prediction is near the upper bound given by CDF Collaboration recently.Comment: 19 pages, 4 figures, some errors corrected; Journal versio
Plaquette order and deconfined quantum critical point in the spin-1 bilinear-biquadratic Heisenberg model on the honeycomb lattice
We have precisely determined the ground state phase diagram of the quantum
spin-1 bilinear-biquadratic Heisenberg model on the honeycomb lattice using the
tensor renormalization group method. We find that the ferromagnetic,
ferroquadrupolar, and a large part of the antiferromagnetic phases are stable
against quantum fluctuations. However, around the phase where the ground state
is antiferroquadrupolar ordered in the classical limit, quantum fluctuations
suppress completely all magnetic orders, leading to a plaquette order phase
which breaks the lattice symmetry but preserves the spin SU(2) symmetry. On the
evidence of our numerical results, the quantum phase transition between the
antiferromagnetic phase and the plaquette phase is found to be either a direct
second order or a very weak first order transition.Comment: 6 pages, 9 figures, published versio
A Comparison of Quintessence and Nonlinear Born-Infeld Scalar Field Using Gold Supernova data
We study the Non-Linear Born-Infeld(NLBI) scalar field model and quintessence
model with two different potentials( and ). We
investigate the differences between those two models. We explore the equation
of state parameter w and the evolution of scale factor in both NLBI
scalar field and quintessence model. The present age of universe and the
transition redshift are also obtained. We use the Gold dataset of 157 SN-Ia to
constrain the parameters of the two models. All the results show that NLBI
model is slightly superior to quintessence model.Comment: 17 pages, 10 figures, some references adde
Some Low Dimensional Evidence for the Weak Gravity Conjecture
We discuss a few examples in 2+1 dimensions and 1+1 dimensions supporting a
recent conjecture concerning the relation between the Planck scale and the
coupling strength of a non-gravitional interaction, unlike those examples in
3+1 dimensions, we do not have to resort to exotic physics such as small black
holes. However, the result concerning these low dimensional examples is a
direct consequence of the 3+1 dimensional conjecture.Comment: 7 pages, harvma
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