5,070 research outputs found
Long-wavelength fluctuations and static correlations in quasi-2D colloidal suspensions
Dimensionality strongly affects thermal fluctuations and critical dynamics of
equilibrium systems. These influences persist in amorphous systems going
through the nonequilibrium glass transition. Here, we experimentally study the
glass transition of quasi-2D suspensions of spherical and ellipsoidal particles
under different degrees of circular confinement. We show that the strength of
the long-wavelength fluctuations increases logarithmically with system sizes
and displays the signature of the Mermin-Wagner fluctuations. Moreover, using
confinement as a tool, we also measure static structural correlations and
extract a growing static correlation length in 2D supercooled liquids. Finally,
we explore the influence of the Mermin-Wagner fluctuations on the translational
and orientational relaxations of 2D ellipsoidal suspensions, which leads to a
new interpretation of the two-step glass transition and the orientational glass
phase of anisotropic particles. Our study reveals the importance of
long-wavelength fluctuations in 2D supercooled liquids and provides new
insights into the role of dimensionality in the glass transition.Comment: 11 pages, 12 figures, Soft Matter (accepted
Baryon Distribution in Galaxy Clusters as a Result of Sedimentation of Helium Nuclei
Heavy particles in galaxy clusters tend to be more centrally concentrated
than light ones according to the Boltzmann distribution. An estimate of the
drift velocity suggests that it is possible that the helium nuclei may have
entirely or partially sedimented into the cluster core within the Hubble time.
We demonstrate the scenario using the NFW profile as the dark matter
distribution of clusters and assuming that the intracluster gas is isothermal
and in hydrostatic equilibrium. We find that a greater fraction of baryonic
matter is distributed at small radii than at large radii, which challenges the
prevailing claim that the baryon fraction increases monotonically with cluster
radius. It shows that the conventional mass estimate using X-ray measurements
of intracluster gas along with a constant mean molecular weight may have
underestimated the total cluster mass by , which in turn leads to an
overestimate of the total baryon fraction by the same percentage. Additionally,
it is pointed out that the sedimentation of helium nuclei toward cluster cores
may at least partially account for the sharp peaks in the central X-ray
emissions observed in some clusters.Comment: 4 pages + 3 figures, minor changes, ApJ Lett., 2000, 529, L
Biaxial-stress driven tetragonal symmetry breaking in and high-temperature ferromagnetic semiconductor from half-metallic CrO2
It is highly desirable to combine the full spin polarization of carriers with
modern semiconductor technology for spintronic applications. For this purpose,
one needs good crystalline ferromagnetic (or ferrimagnetic) semiconductors with
high Curie temperatures. Rutile CrO is a half-metallic spintronic material
with Curie temperature 394 K and can have nearly-full spin polarization at room
temperature. Here, we find through first-principles investigation that when a
biaxial compressive stress is applied on rutile CrO, the density of states
at the Fermi level decreases with the in-plane compressive strain, there is a
structural phase transition to an orthorhombic phase at the strain of -5.6\%,
and then appears an electronic phase transition to a semiconductor phase at
-6.1\%. Further analysis shows that this structural transition, accompanying
the tetragonal symmetry breaking, is induced by the stress-driven distortion
and rotation of the oxygen octahedron of Cr, and the half-metal-semiconductor
transition originates from the enhancement of the crystal field splitting due
to the structural change. Importantly, our systematic total-energy comparison
indicates the ferromagnetic Curie temperature remains almost independent of the
strain, near 400 K. This biaxial stress can be realized by applying biaxial
pressure or growing the CrO epitaxially on appropriate substrates. These
results should be useful for realizing full (100\%) spin polarization of
controllable carriers as one uses in modern semiconductor technology.Comment: 7 pages, 7 figure
Identifying spatial invasion of pandemics on metapopulation networks via anatomizing arrival history
Spatial spread of infectious diseases among populations via the mobility of
humans is highly stochastic and heterogeneous. Accurate forecast/mining of the
spread process is often hard to be achieved by using statistical or mechanical
models. Here we propose a new reverse problem, which aims to identify the
stochastically spatial spread process itself from observable information
regarding the arrival history of infectious cases in each subpopulation. We
solved the problem by developing an efficient optimization algorithm based on
dynamical programming, which comprises three procedures: i, anatomizing the
whole spread process among all subpopulations into disjoint componential
patches; ii, inferring the most probable invasion pathways underlying each
patch via maximum likelihood estimation; iii, recovering the whole process by
assembling the invasion pathways in each patch iteratively, without burdens in
parameter calibrations and computer simulations. Based on the entropy theory,
we introduced an identifiability measure to assess the difficulty level that an
invasion pathway can be identified. Results on both artificial and empirical
metapopulation networks show the robust performance in identifying actual
invasion pathways driving pandemic spread.Comment: 14pages, 8 figures; Accepted by IEEE Transactions on Cybernetic
SilentSense: Silent User Identification via Dynamics of Touch and Movement Behavioral Biometrics
With the increased popularity of smartphones, various security threats and
privacy leakages targeting them are discovered and investigated. In this work,
we present \ourprotocoltight, a framework to authenticate users silently and
transparently by exploiting dynamics mined from the user touch behavior
biometrics and the micro-movement of the device caused by user's screen-touch
actions. We build a "touch-based biometrics" model of the owner by extracting
some principle features, and then verify whether the current user is the owner
or guest/attacker. When using the smartphone, the unique operating dynamics of
the user is detected and learnt by collecting the sensor data and touch events
silently. When users are mobile, the micro-movement of mobile devices caused by
touch is suppressed by that due to the large scale user-movement which will
render the touch-based biometrics ineffective. To address this, we integrate a
movement-based biometrics for each user with previous touch-based biometrics.
We conduct extensive evaluations of our approaches on the Android smartphone,
we show that the user identification accuracy is over 99%
Long-lived quantum coherence of two-level spontaneous emission models within structured environments
We investigate the long-lived quantum coherence of two-level spontaneous
emission models within structured environments. The population of the system
under the asymptotic non-Markovian dynamics is linked to the spectral density
of the reservoir through a general functional relation between them. We figure
out explicitly the preservation of quantum coherence, via notions of
entanglement and quantum discord, in connection with the spectral parameters of
Ohmic class reservoirs and then show how to achieve them optimally. We expect
these results to contribute towards reservoir engineering with the aim of
enhancing stationary quantum coherence in noisy environments.Comment: 4 pages, 2 figures, accepted by Opt. Let
The algebra A_{\hbar,\eta}(\hat{g}) and Infinite Hopf family of algebras
New deformed affine algebras A_{\hbar,\eta}(\hat{g}) are defined for any
simply-laced classical Lie algebra g, which are generalizations of the algebra
A_{\hbar,\eta}(\hat{sl_2}) recently proposed by Khoroshkin, Lebedev and
Pakuliak (KLP). Unlike the work of KLP, we associate to the new algebras the
structure of an infinite Hopf family of algebras in contrast to the one
containing only finite number of algebras introduced by KLP. Bosonic
representation for A_{\hbar,\eta}(\hat{g}) at level 1 is obtained, and it is
shown that, by repeated application of Drinfeld-like comultiplications, a
realization of A_{\hbar,\eta}(\hat{g}) at any positive integer level can be
obtained. For the special case of g=sl_{r+1}, (r+1)-dimensional evaluation
representation is given. The corresponding intertwining operators are defined
and the intertwining relations are also derived explicitly.Comment: This version has been completely revised. Many corrections are made.
In the title we add the word "infinite" to show the difference from
Khoroshkin et al. LaTeX, 23 page
q-affine-Yangian double correspondence and free boson representation of Yangian double with arbitrary level
We derive a free boson representation of the Yangian double
with arbitrary level k using the observation that there is a correspondence
between the q-affine algebra and Yangian double associated with the same Cartan
matrix. Vertex operator and screening currents are not obtained in the same
way.Comment: LaTeX file, amssymb and amsart used. 13 pages, no figures. Several
misprints corrected, some in important formula
Quantum currents in the Coset Space SU(2)/U(1)
We propose a rational quantum deformed nonlocal currents in the homogenous
space , and in terms of it and a free boson field a
representation for the Drinfeld currents of Yangian double at a general level
is obtained. In the classical limit , the quantum nonlocal
currents become parafermion, and the realization of Yangian double
becomes the parafermion realization of current algebra.Comment: Latex, 9 page
High-spin mesons below 3 GeV
In this work, we study the high-spin states with masses below 3 GeV observed
in experiments and we perform analysis of mass spectrum and investigation of
strong decay behaviors of the high-spin states. Comparing our results with the
experimental data, we can reveal the underlying properties of these high-spin
states; more importantly, we also predict their abundant decay features, which
can provide valuable information for experimental exploration of these
high-spin states.Comment: 17 pages, 15 figures and 4 tables. More discussions added. Accepted
by Phys. Rev.
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