13,225 research outputs found
Strong Correlation to Weak Correlation Phase Transition in Bilayer Quantum Hall Systems
At small layer separations, the ground state of a nu=1 bilayer quantum Hall
system exhibits spontaneous interlayer phase coherence and has a
charged-excitation gap E_g. The evolution of this state with increasing layer
separation d has been a matter of controversy. In this letter we report on
small system exact diagonalization calculations which suggest that a single
phase transition, likely of first order, separates coherent incompressible (E_g
>0) states with strong interlayer correlations from incoherent compressible
states with weak interlayer correlations. We find a dependence of the phase
boundary on d and interlayer tunneling amplitude that is in very good agreement
with recent experiments.Comment: 4 pages, 4 figures included, version to appear in Phys. Rev. Let
Resonances of the cusp family
We study a family of chaotic maps with limit cases the tent map and the cusp
map (the cusp family). We discuss the spectral properties of the corresponding
Frobenius--Perron operator in different function spaces including spaces of
analytic functions. A numerical study of the eigenvalues and eigenfunctions is
performed.Comment: 14 pages, 3 figures. Submitted to J.Phys.
Compaction and dilation rate dependence of stresses in gas-fluidized beds
A particle dynamics-based hybrid model, consisting of monodisperse spherical
solid particles and volume-averaged gas hydrodynamics, is used to study
traveling planar waves (one-dimensional traveling waves) of voids formed in
gas-fluidized beds of narrow cross sectional areas. Through ensemble-averaging
in a co-traveling frame, we compute solid phase continuum variables (local
volume fraction, average velocity, stress tensor, and granular temperature)
across the waves, and examine the relations among them. We probe the
consistency between such computationally obtained relations and constitutive
models in the kinetic theory for granular materials which are widely used in
the two-fluid modeling approach to fluidized beds. We demonstrate that solid
phase continuum variables exhibit appreciable ``path dependence'', which is not
captured by the commonly used kinetic theory-based models. We show that this
path dependence is associated with the large rates of dilation and compaction
that occur in the wave. We also examine the relations among solid phase
continuum variables in beds of cohesive particles, which yield the same path
dependence. Our results both for beds of cohesive and non-cohesive particles
suggest that path-dependent constitutive models need to be developed.Comment: accepted for publication in Physics of Fluids (Burnett-order effect
analysis added
Quantum Numbers of Textured Hall Effect Quasiparticles
We propose a class of variational wave functions with slow variation in spin
and charge density and simple vortex structure at infinity, which properly
generalize both the Laughlin quasiparticles and baby Skyrmions. We argue that
the spin of the corresponding quasiparticle has a fractional part related in a
universal fashion to the properties of the bulk state, and propose a direct
experimental test of this claim. We show that certain spin-singlet quantum Hall
states can be understood as arising from primary polarized states by Skyrmion
condensation.Comment: 13 pages, no figures, Phyzz
The black hole final state for the Dirac fields In Schwarzschild spacetime
We show that the internal stationary state of a black hole for massless Dirac
fields can be represented by an entangled state of collapsing matter and
infalling Hawking radiation. This implies that the Horowitz-Maldacena
conjecture for the black hole final state originally proposed for the massless
scalar fields is also applicable to fermionic fields as well. For an initially
mixed state we find that the measure of mixedness is expected to decrease under
evaporation
Optical observations of NEA 162173 (1999 JU3) during the 2011-2012 apparition
Near-Earth asteroid 162173 (1999 JU3) is a potential target of two asteroid
sample return missions, not only because of its accessibility but also because
of the first C-type asteroid for exploration missions. The lightcurve-related
physical properties of this object were investigated during the 2011-2012
apparition. We aim to confirm the physical parameters useful for JAXA's
Hayabusa 2 mission, such as rotational period, absolute magnitude, and phase
function. Our data complement previous studies that did not cover low phase
angles. With optical imagers and 1-2 m class telescopes, we acquired the
photometric data at different phase angles. We independently derived the
rotational lightcurve and the phase curve of the asteroid. We have analyzed the
lightcurve of 162173 (1999 JU3), and derived a synodic rotational period of
7.625 +/- 0.003 h, the axis ratio a/b = 1.12. The absolute magnitude H_R =
18.69 +/- 0.07 mag and the phase slope of G = -0.09 +/- 0.03 were also obtained
based on the observations made during the 2011-2012 apparition.Comment: 4 pages, 3 figure
Time-delayed Spatial Patterns in a Two-dimensional Array of Coupled Oscillators
We investigated the effect of time delays on phase configurations in a set of
two-dimensional coupled phase oscillators. Each oscillator is allowed to
interact with its neighbors located within a finite radius, which serves as a
control parameter in this study. It is found that distance-dependent
time-delays induce various patterns including traveling rolls, square-like and
rhombus-like patterns, spirals, and targets. We analyzed the stability
boundaries of the emerging patterns and briefly pointed out the possible
empirical implications of such time-delayed patterns.Comment: 5 Figure
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