34,555 research outputs found
Irrational charge from topological order
Topological or deconfined phases of matter exhibit emergent gauge fields and
quasiparticles that carry a corresponding gauge charge. In systems with an
intrinsic conserved U(1) charge, such as all electronic systems where the
Coulombic charge plays this role, these quasiparticles are also characterized
by their intrinsic charge. We show that one can take advantage of the
topological order fairly generally to produce periodic Hamiltonians which endow
the quasiparticles with continuously variable, generically irrational,
intrinsic charges. Examples include various topologically ordered lattice
models, the three dimensional RVB liquid on bipartite lattices as well as water
and spin ice. By contrast, the gauge charges of the quasiparticles retain their
quantized values.Comment: 4 pages, 1 figure with two panel
Structure and stability of quasi-two-dimensional boson-fermion mixtures with vortex-antivortex superposed states
We investigate the equilibrium properties of a quasi-two-dimensional
degenerate boson-fermion mixture (DBFM) with a bosonic vortex-antivortex
superposed state (VAVSS) using a quantum-hydrodynamic model. We show that,
depending on the choice of parameters, the DBFM with a VAVSS can exhibit rich
phase structures. For repulsive boson-fermion (BF) interaction, the
Bose-Einstein condensate (BEC) may constitute a petal-shaped "core" inside the
honeycomb-like fermionic component, or a ring-shaped joint "shell" around the
onion-like fermionic cloud, or multiple segregated "islands" embedded in the
disc-shaped Fermi gas. For attractive BF interaction just below the threshold
for collapse, an almost complete mixing between the bosonic and fermionic
components is formed, where the fermionic component tends to mimic a bosonic
VAVSS. The influence of an anharmonic trap on the density distributions of the
DBFM with a bosonic VAVSS is discussed. In addition, a stability region for
different cases of DBFM (without vortex, with a bosonic vortex, and with a
bosonic VAVSS) with specific parameters is given.Comment: 8 pages,5 figure
Spin-dependent tunneling through a symmetric semiconductor barrier: the Dresselhaus effect
Spin-dependent tunneling through a symmetric semiconductor barrier is studied
including the k^3 Dresselhaus effect. The spin-dependent transmission of
electron can be obtained analytically. By comparing with previous work(Phys.
Rev. B 67. R201304 (2003) and Phys. Rev. Lett. 93. 056601 (2004)), it is shown
that the spin polarization and interface current are changed significantly by
including the off-diagonal elements in the current operator, and can be
enhanced considerably by the Dresselhaus effect in the contact regions.Comment: 10 pages, 5 figures, to appear in PR
Geometrical Expression for the Angular Resolution of a Network of Gravitational-Wave Detectors
We report for the first time general geometrical expressions for the angular
resolution of an arbitrary network of interferometric gravitational-wave (GW)
detectors when the arrival-time of a GW is unknown. We show explicitly elements
that decide the angular resolution of a GW detector network. In particular, we
show the dependence of the angular resolution on areas formed by projections of
pairs of detectors and how they are weighted by sensitivities of individual
detectors. Numerical simulations are used to demonstrate the capabilities of
the current GW detector network. We confirm that the angular resolution is poor
along the plane formed by current LIGO-Virgo detectors. A factor of a few to
more than ten fold improvement of the angular resolution can be achieved if the
proposed new GW detectors LCGT or AIGO are added to the network. We also
discuss the implications of our results for the design of a GW detector
network, optimal localization methods for a given network, and electromagnetic
follow-up observations.Comment: 13 pages, for Phys. Rev.
Light cone dynamics and reverse Kibble-Zurek mechanism in two-dimensional superfluids following a quantum quench
We study the dynamics of the relative phase of a bilayer of two-dimensional
superfluids after the two superfluids have been decoupled. We find that on
short time scales the relative phase shows "light cone" like dynamics and
creates a metastable superfluid state, which can be supercritical. We also
demonstrate similar light cone dynamics for the transverse field Ising model.
On longer time scales the supercritical state relaxes to a disordered state due
to dynamical vortex unbinding. This scenario of dynamically suppressed vortex
proliferation constitutes a reverse-Kibble-Zurek effect. We study this effect
both numerically using truncated Wigner approximation and analytically within a
newly suggested time dependent renormalization group approach (RG). In
particular, within RG we show that there are two possible fixed points for the
real time evolution corresponding to the superfluid and normal steady states.
So depending on the initial conditions and the microscopic parameters of the
Hamiltonian the system undergoes a non-equilibrium phase transition of the
Kosterlitz-Thouless type. The time scales for the vortex unbinding near the
critical point are exponentially divergent, similar to the equilibrium case.Comment: 14 pages, 10 figure
Resonating singlet valence plaquettes
We consider the simplest generalizations of the valence bond physics of SU(2)
singlets to SU(N) singlets that comprise objects with N sites -- these are
SU(N) singlet plaquettes with N=3 and N=4 in three spatial dimensions.
Specifically, we search for a quantum mechanical liquid of such objects -- a
resonating singlet valence plaquette phase that generalizes the celebrated
resonating valence bond phase for SU(2) spins. We extend the Rokhsar-Kivelson
construction of the quantum dimer model to the simplest SU(4) model for valence
plaquette dynamics on a cubic lattice. The phase diagram of the resulting
quantum plaquette model is analyzed both analytically and numerically. We find
that the ground state is solid everywhere, including at the Rokhsar-Kivelson
point where the ground state is an equal amplitude sum. By contrast, the equal
amplitude sum of SU(3) singlet triangular plaquettes on the face centered cubic
lattice is liquid and thus a candidate for describing a resonating single
valence plaquette phase, given a suitably defined local Hamiltonian.Comment: 12 pages, 15 figures, minor changes, references added, Phys Rev B
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Food Consumption and Demographics in Japan: Implications for an Aging Population
This study estimates a cross-sectional model based on the Almost Ideal Demand System (AIDS) to examine the determinants of food consumption patterns in Japan over life-cycle periods. The test of structural changes, the analysis of the effects of demographic characteristics, and the estimation of expenditure and price elasticities are conducted from a random sample of 1,281 households from a Japanese household survey in 1997. Results show that each economic or non-economic factor has a different impact on food consumption over a lifetime. Changes in consumption of some food groups can be explained by price and income effects where others can be explained by demographic characteristics. Financial constraint is not binding and residential location is likely to have little or no impact on predicting consumers’ food choices at different periods of their lives. Other key factors that affect consumption pattern include family size, number of children, lifestyle and health concern.Japan, Food Demand, Life-Cycle, AIDS, Household
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