13,080 research outputs found
Density Power Spectrum of Compressible Hydrodynamic Turbulent Flows
Turbulent flows are ubiquitous in astrophysical environments, and
understanding density structures and their statistics in turbulent media is of
great importance in astrophysics. In this paper, we study the density power
spectra, , of transonic and supersonic turbulent flows through one
and three-dimensional simulations of driven, isothermal hydrodynamic turbulence
with root-mean-square Mach number in the range of 1 \la M_{\rm rms} \la 10.
From one-dimensional experiments we find that the slope of the density power
spectra becomes gradually shallower as the rms Mach number increases. It is
because the density distribution transforms from the profile with {\it
discontinuities} having for to
the profile with {\it peaks} having for . We also find that the same trend is carried to three-dimension; that is,
the density power spectrum flattens as the Mach number increases. But the
density power spectrum of the flow with has the Kolmogorov
slope. The flattening is the consequence of the dominant density structures of
{\it filaments} and {\it sheets}. Observations have claimed different slopes of
density power spectra for electron density and cold H I gas in the interstellar
medium. We argue that while the Kolmogorov spectrum for electron density
reflects the {\it transonic} turbulence of in the warm
ionized medium, the shallower spectrum of cold H I gas reflects the {\it
supersonic} turbulence of a few in the cold neutral medium.Comment: To appear in ApJ Lett. Pdf file with full resolution figures can be
downloaded from http://canopus.cnu.ac.kr/ryu/kimryu.pd
P04.63. The consciousness of medical doctors about collaborative practice of Western medicine and traditional Korean medicine
Minimax optimization of entanglement witness operator for the quantification of three-qubit mixed-state entanglement
We develop a numerical approach for quantifying entanglement in mixed quantum
states by convex-roof entanglement measures, based on the optimal entanglement
witness operator and the minimax optimization method. Our approach is
applicable to general entanglement measures and states and is an efficient
alternative to the conventional approach based on the optimal pure-state
decomposition. Compared with the conventional one, it has two important merits:
(i) that the global optimality of the solution is quantitatively verifiable,
and (ii) that the optimization is considerably simplified by exploiting the
common symmetry of the target state and measure. To demonstrate the merits, we
quantify Greenberger-Horne-Zeilinger (GHZ) entanglement in a class of
three-qubit full-rank mixed states composed of the GHZ state, the W state, and
the white noise, the simplest mixtures of states with different genuine
multipartite entanglement, which have not been quantified before this work. We
discuss some general properties of the form of the optimal witness operator and
of the convex structure of mixed states, which are related to the symmetry and
the rank of states
COMPARISON OF KNEE JOINT MONENTS DURING ANTICIPATED AND UNANTICIPATED RUNNING AND CUTTING MANEUVER - A PILOT STUDY
INTRODUCTION: Knee joint injuries are common in sports activities. Because it is understood that non-contact ACL injuries most often occur during cutting or landing tasks, biomechanical studies have examined in lower extremity kinematics. Cutting maneuvers during sporting are not always anticipated, and usually occur as a sudden reaction to an external stimulus. Therefore, the purpose of this study was to compare the joint moments in the lower extremity of females during anticipated and unanticipated running and cutting manoeuvres
Algebraic vortex liquid theory of a quantum antiferromagnet on the kagome lattice
There is growing evidence from both experiment and numerical studies that low
half-odd integer quantum spins on a kagome lattice with predominant
antiferromagnetic near neighbor interactions do not order magnetically or break
lattice symmetries even at temperatures much lower than the exchange
interaction strength. Moreover, there appear to be a plethora of low energy
excitations, predominantly singlets but also spin carrying, which suggest that
the putative underlying quantum spin liquid is a gapless ``critical spin
liquid'' rather than a gapped spin liquid with topological order. Here, we
develop an effective field theory approach for the spin-1/2 Heisenberg model
with easy-plane anisotropy on the kagome lattice. By employing a vortex duality
transformation, followed by a fermionization and flux-smearing, we obtain
access to a gapless yet stable critical spin liquid phase, which is described
by (2+1)-dimensional quantum electrodynamics (QED) with an emergent
flavor symmetry. The specific heat, thermal conductivity, and
dynamical structure factor are extracted from the effective field theory, and
contrasted with other theoretical approaches to the kagome antiferromagnet.Comment: 14 pages, 8 figure
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