36,381 research outputs found
Phonon-induced quadrupolar ordering of the magnetic superconductor TmNiBC
We present synchrotron x-ray diffraction studies revealing that the lattice
of thulium borocarbide is distorted below T_Q = 13.5 K at zero field. T_Q
increases and the amplitude of the displacements is drastically enhanced, by a
factor of 10 at 60 kOe, when a magnetic field is applied along [100]. The
distortion occurs at the same wave vector as the antiferromagnetic ordering
induced by the a-axis field. A model is presented that accounts for the
properties of the quadrupolar phase and explains the peculiar behavior of the
antiferromagnetic ordering previously observed in this compound.Comment: submitted to PR
Self-Organized Dynamical Equilibrium in the Corrosion of Random Solids
Self-organized criticality is characterized by power law correlations in the
non-equilibrium steady state of externally driven systems. A dynamical system
proposed here self-organizes itself to a critical state with no characteristic
size at ``dynamical equilibrium''. The system is a random solid in contact with
an aqueous solution and the dynamics is the chemical reaction of corrosion or
dissolution of the solid in the solution. The initial difference in chemical
potential at the solid-liquid interface provides the driving force. During time
evolution, the system undergoes two transitions, roughening and
anti-percolation. Finally, the system evolves to a dynamical equilibrium state
characterized by constant chemical potential and average cluster size. The
cluster size distribution exhibits power law at the final equilibrium state.Comment: 11 pages, 5 figure
On the definition of Quantum Free Particle on Curved Manifolds
A selfconsistent definition of quantum free particle on a generic curved
manifold emerges naturally by restricting the dynamics to submanifolds of
co-dimension one.
PACS 0365 0240Comment: 8 p., phyzzx macropackag
On the number of contacts of a floating polymer chain cross-linked with a surface adsorbed chain on fractal structures
We study the interaction problem of a linear polymer chain, floating in
fractal containers that belong to the three-dimensional Sierpinski gasket (3D
SG) family of fractals, with a surface-adsorbed linear polymer chain. Each
member of the 3D SG fractal family has a fractal impenetrable 2D adsorbing
surface, which appears to be 2D SG fractal. The two-polymer system is modelled
by two mutually crossing self-avoiding walks. By applying the Monte Carlo
Renormalization Group (MCRG) method, we calculate the critical exponents
, associated with the number of contacts of the 3D SG floating polymer
chain, and the 2D SG adsorbed polymer chain, for a sequence of SG fractals with
. Besides, we propose the codimension additivity (CA) argument
formula for , and compare its predictions with our reliable set of the
MCRG data. We find that monotonically decreases with increasing ,
that is, with increase of the container fractal dimension. Finally, we discuss
the relations between different contact exponents, and analyze their possible
behaviour in the fractal-to-Euclidean crossover region .Comment: 15 pages, 3 figure
Role of Activity in Human Dynamics
The human society is a very complex system; still, there are several
non-trivial, general features. One type of them is the presence of power-law
distributed quantities in temporal statistics. In this Letter, we focus on the
origin of power-laws in rating of movies. We present a systematic empirical
exploration of the time between two consecutive ratings of movies (the
interevent time). At an aggregate level, we find a monotonous relation between
the activity of individuals and the power-law exponent of the interevent-time
distribution. At an individual level, we observe a heavy-tailed distribution
for each user, as well as a negative correlation between the activity and the
width of the distribution. We support these findings by a similar data set from
mobile phone text-message communication. Our results demonstrate a significant
role of the activity of individuals on the society-level patterns of human
behavior. We believe this is a common character in the interest-driven human
dynamics, corresponding to (but different from) the universality classes of
task-driven dynamics.Comment: 5 pages, 6 figures. Accepted by EP
Precision Measurement of the Spin-Dependent Asymmetry in the Threshold Region of ^3He(e, e')
We present the first precision measurement of the spin-dependent asymmetry in the threshold region of ^3He(e,e′) at Q^2 values of 0.1 and 0.2(GeV/c)^2. The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q^2 = 0.1(GeV/c)^2, while a small discrepancy at Q^2 = 0.2(GeV/c)^2 is observed
Shell-Model Effective Operators for Muon Capture in ^{20}Ne
It has been proposed that the discrepancy between the partially-conserved
axial-current prediction and the nuclear shell-model calculations of the ratio
in the muon-capture reactions can be solved in the case of ^{28}Si by
introducing effective transition operators. Recently there has been
experimental interest in measuring the needed angular correlations also in
^{20}Ne. Inspired by this, we have performed a shell-model analysis employing
effective transition operators in the shell-model formalism for the transition
. Comparison of
the calculated capture rates with existing data supports the use of effective
transition operators. Based on our calculations, as soon as the experimental
anisotropy data becomes available, the limits for the ratio can be
extracted.Comment: 9 pages, 3 figures include
Mode-locking in ac-driven vortex lattices with random pinning
We find mode-locking steps in simulated current-voltage characteristics of
ac-driven vortex lattices with {\it random} pinning. For low frequencies there
is mode-locking above a finite ac force amplitude, while for large frequencies
there is mode-locking for any small ac force. This is correlated with the
nature of temporal order in the different regimes in the absence of ac drive.
The mode-locked state is a frozen solid pinned in the moving reference of
frame, and the depinning from the step shows plastic flow and hysteresis.Comment: 4 pages, 4 figure
Weakly bound states of polar molecules in bilayers
We investigate a system of two polarized molecules in a layered trap. The
molecules reside in adjacent layers and interact purely via the dipole-dipole
interaction. We determine the properties of the ground state of the system as a
function of the dipole moment and polarization angle. A bound state is always
present in the system and in the weak binding limit the bound state extends to
a very large distance and shows universal behavior.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
Braided Rivers and Superconducting Vortex Avalanches
Magnetic vortices intermittently flow through preferred channels when they
are forced in or out of a superconductor. We study this behavior using a
cellular model, and find that the vortex flow can make braided rivers
strikingly similar to aerial photographs of braided fluvial rivers, such as the
Brahmaputra. By developing an analysis technique suitable for characterizing a
self-affine (multi)fractal, the scaling properties of the braided vortex rivers
in the model are compared with those of braided fluvial rivers. We suggest that
avalanche dynamics leads to braiding in both cases.Comment: 4 pages, 3 figures. To appear in PR
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