18,652 research outputs found
Multipartite entanglement of fermionic systems in noninertial frames
The bipartite and tripartite entanglement of a 3-qubit fermionic system when
one or two subsystems accelerated are investigated. It is shown that all the
one-tangles decrease as the acceleration increases. However, unlike the scalar
case, here one-tangles and never
reduce to zero for any acceleration. It is found that the system has only
tripartite entanglement when either one or two subsystems accelerated, which
means that the acceleration doesn't generate bipartite entanglement and doesn't
effect the entanglement structure of the quantum states in this system. It is
of interest to note that the -tangle of the two-observers-accelerated case
decreases much quicker than that of the one-observer-accelerated case and it
reduces to a non-zero minimum in the infinite acceleration limit. Thus we argue
that the qutrit systems are better than qubit systems to perform quantum
information processing tasks in noninertial systems.Comment: 12 pages, 3 figure
Statistical study of free magnetic energy and flare productivity of solar active regions
Photospheric vector magnetograms from Helioseismic and Magnetic Imager on
board the Solar Dynamic Observatory are utilized as the boundary conditions to
extrapolate both non-linear force-free and potential magnetic fields in solar
corona. Based on the extrapolations, we are able to determine the free magnetic
energy (FME) stored in active regions (ARs). Over 3000 vector magnetograms in
61 ARs were analyzed. We compare FME with ARs' flare index (FI) and find that
there is a weak correlation () between FME and FI. FME shows slightly
improved flare predictability relative to total unsigned magnetic flux of ARs
in the following two aspects: (1) the flare productivity predicted by FME is
higher than that predicted by magnetic flux and (2) the correlation between FI
and FME is higher than that between FI and magnetic flux. However, this
improvement is not significant enough to make a substantial difference in
time-accumulated FI, rather than individual flare, predictions.Comment: The paper was submitted to ApJ and it is accepted no
Quantum speed limit for relativistic spin-0 and spin-1 bosons on commutative and noncommutative planes
Quantum speed limits of relativistic charged spin-0 and spin-1 bosons in the
background of a homogeneous magnetic field are studied on both commutative and
oncommutative planes. We show that, on the commutative plane, the average
speeds of wave packets along the radial direction during the interval in which
a quantum state evolving from an initial state to the orthogonal final one can
not exceed the speed of light, regardless of the intensities of the magnetic
field. However, due to the noncommutativity, the average speeds of the wave
packets on noncommutative plane will exceed the speed of light in vacuum
provided the intensity of the magnetic field is strong enough. It is a clear
signature of violating Lorentz invariance in quantum mechanics region.Comment: 8 pages, no figures. arXiv admin note: text overlap with
arXiv:1702.0316
The distribution of ejected subhalos and its implication for halo assembly bias
Using a high-resolution cosmological -body simulation, we identify the
ejected population of subhalos, which are halos at redshift but were once
contained in more massive `host' halos at high redshifts. The fraction of the
ejected subhalos in the total halo population of the same mass ranges from 9%
to 4% for halo masses from to \sim 10^{12}\msun. Most of the
ejected subhalos are distributed within 4 times the virial radius of their
hosts. These ejected subhalos have distinct velocity distribution around their
hosts in comparison to normal halos. The number of subhalos ejected from a host
of given mass increases with the assembly redshift of the host. Ejected
subhalos in general reside in high-density regions, and have a much higher bias
parameter than normal halos of the same mass. They also have earlier assembly
times, so that they contribute to the assembly bias of dark matter halos seen
in cosmological simulations. However, the assembly bias is {\it not} dominated
by the ejected population, indicating that large-scale environmental effects on
normal halos are the main source for the assembly bias.Comment: revised version, submitted to MNRA
A maze of contradictions: Chinese law and policy in the development process of privately owned small and medium-sized enterprises in China
This article looks at flaws in theLaw of China on Promotion of Small and Medium-Sized Enterprises 2002 (the Chinese Law on Promotion of SMEs 2002) and the Anti-Monopoly Law of China 2007 (the Chinese Anti-Monopoly Law 2007), as well as examining the inconsistencies between the State's industrial policy and the current legal framework for Chinese privately owned SMEs. Although legal protection for SMEs is not a new research area in China, little scholarship has been devoted to conflicts between "law" and 'policy" from a relationship standpoint between State-owned enterprises (SOEs) and privately owned SMEs. It argues that these SMEs are less able than SOEs to obtain chances for robust growth due to their privileges and immunities. By ignoring the market function, but emphasizing the economic role of the State, and by offering no genuine sanctions for senseless intervention from the State's industrial policy, the Chinese Law on Promotion of SMEs 2002 and the Chinese Anti-Monopoly Law 2007 fail to establish fair competition circumstances for privately owned SMEs. Why cannot these two laws overcome the State's industrial policy? Different approaches to achieving dissimilar goals in the Chinese market would be the answer. Thus, this article demonstrates that administrative powers granted by the State's industrial policy are the biggest obstacle for privately owned SMEs, and then recommends methods to resolve this dilemma from the perspective of the Chinese Anti-Monopoly Law 2007
Environmental Dependence of Cold Dark Matter Halo Formation
We use a high-resolution -body simulation to study how the formation of
cold dark matter (CDM) halos is affected by their environments, and how such
environmental effects produce the age-dependence of halo clustering observed in
recent -body simulations. We estimate, for each halo selected at redshift
, an `initial' mass defined to be the mass enclosed by the
largest sphere which contains the initial barycenter of the halo particles and
within which the mean linear density is equal to the critical value for
spherical collapse at . For halos of a given final mass, , the
ratio has large scatter, and the scatter is larger for
halos of lower final masses. Halos that form earlier on average have larger
, and so correspond to higher peaks in the initial density
field than their final masses imply. Old halos are more strongly clustered than
younger ones of the same mass because their initial masses are larger. The
age-dependence of clustering for low-mass halos is entirely due to the
difference in the initial/final mass ratio. Low-mass old halos are almost
always located in the vicinity of big structures, and their old ages are
largely due to the fact that their mass accretions are suppressed by the hot
environments produced by the tidal fields of the larger structure. The
age-dependence of clustering is weaker for more massive halos because the
heating by large-scale tidal fields is less important.Comment: 18 pages,19 figures, accepted by MNRA
Influence of Fermion Velocity Renormalization on Dynamical Mass Generation in QED
We study dynamical fermion mass generation in (2+1)-dimensional quantum
electrodynamics with a gauge field coupling to massless Dirac fermions and
non-relativistic scalar bosons. We calculate the fermion velocity
renormalization and then examine its influence on dynamical mass generation by
using the Dyson-Schwinger equation. It is found that dynamical mass generation
takes place even after including the scalar bosons as long as the bosonic
compressibility parameter is sufficiently small. In addition, the fermion
velocity renormalization enhances the dynamically generated mass.Comment: 6 pages, 3 figures, Chinese Physics Letter, Vol 29, page 057401(2012
The Hunter-Saxton equation: remarkable structures of symmetries and conserved densities
In this paper, we present extraordinary algebraic and geometrical structures
for the Hunter-Saxton equation: infinitely many commuting and non-commuting
-independent higher order symmetries and conserved densities. Using a
recursive relation, we explicitly generate infinitely many higher order
conserved densities dependent on arbitrary parameters. We find three Nijenhuis
recursion operators resulting from Hamiltonian pairs, of which two are new.
They generate three hierarchies of commuting local symmetries. Finally, we give
a local recursion operator depending on an arbitrary parameter.
As a by-product, we classify all anti-symmetric operators of a definite form
that are compatible with the Hamiltonian operator
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