67,544 research outputs found
Luttinger States at the Edge
An effective wavefunction for the edge excitations in the Fractional quantum
Hall effect can be found by dimensionally reducing the bulk wavefunction.
Treated this way the Laughlin wavefunction yields a Luttinger
model ground state. We identify the edge-electron field with a Luttinger
hyper-fermion operator, and the edge electron itself with a non-backscattering
Bogoliubov quasi-particle. The edge-electron propagator may be calculated
directly from the effective wavefunction using the properties of a
one-dimensional one-component plasma, provided a prescription is adopted which
is sensitive to the extra flux attached to the electrons
Television viewing time and risk of incident obesity and central obesity: the English longitudinal study of ageing
Background Research suggests television viewing time may be associated with incident obesity and central obesity in young adults. No study has investigated these associations in older English adults. The aim of this study was to investigate longitudinal associations between television viewing time and incident obesity and central obesity in a sample of older English adults. Analyses of data from the English Longitudinal Study of Ageing. At baseline (2008), participants reported their television viewing time. Research nurses recorded obesity and central obesity by body mass index and waist circumference, respectively, at four year follow-up. Associations between television viewing time and incident obesity (BMI > 30 kg/m2) and central obesity (waist >102 cm men; > 88 cm women) at four year follow-up were examined using adjusted logistic regression. Participants gave full written informed consent to participate in the study and ethical approval was obtained from the London Multicentre Research Ethics Committee. Results A total of 3777 initially non-obese participants (aged 64.8 ± 8.6 yrs, 46.4% male) were included in the analyses using BMI as an outcome and 2947 for the analyses using waist circumference. No significant associations were found between television viewing time and incident obesity. A significant association was found between watching ≥6 hrs/d of television (compared to <2 hrs/d) and central obesity (Odds Ratio 1.48; 95% confidence interval 1.07 to 2.03) after adjustment for covariables including physical activity. Conclusions In this sample of older community dwelling English adults greater television viewing time was associated with incident central obesity, but not total obesity when measured by BMI. Interventions to reduce the incidence of central obesity in this age group that focus on reducing TV time, as well as targeting other health behaviours (eg, increasing physical activity levels, improving dietary intake) might prove useful
Scaling and interaction-assisted transport in graphene with one-dimensional defects
We analyze the scattering from one-dimensional defects in intrinsic graphene.
The Coulomb repulsion between electrons is found to be able to induce
singularities of such scattering at zero temperature as in one-dimensional
conductors. In striking contrast to electrons in one space dimension, however,
repulsive interactions here can enhance transport. We present explicit
calculations for the scattering from vector potentials that appear when strips
of the material are under strain. There the predicted effects are exponentially
large for strong scatterers.Comment: 4 pages, 2 figure
Numerical Results for the Ground-State Interface in a Random Medium
The problem of determining the ground state of a -dimensional interface
embedded in a -dimensional random medium is treated numerically. Using a
minimum-cut algorithm, the exact ground states can be found for a number of
problems for which other numerical methods are inexact and slow. In particular,
results are presented for the roughness exponents and ground-state energy
fluctuations in a random bond Ising model. It is found that the roughness
exponent , with the related energy
exponent being , in ,
respectively. These results are compared with previous analytical and numerical
estimates.Comment: 10 pages, REVTEX3.0; 3 ps files (separate:tar/gzip/uuencoded) for
figure
Quantum critical phenomena of long-range interacting bosons in a time-dependent random potential
We study the superfluid-insulator transition of a particle-hole symmetric
system of long-range interacting bosons in a time-dependent random potential in
two dimensions, using the momentum-shell renormalization-group method. We find
a new stable fixed point with non-zero values of the parameters representing
the short- and long-range interactions and disorder when the interaction is
asymptotically logarithmic. This is contrasted to the non-random case with a
logarithmic interaction, where the transition is argued to be first-order, and
to the Coulomb interaction case, where either a first-order transition or
an XY-like transition is possible depending on the parameters. We propose that
our model may be relevant in studying the vortex liquid-vortex glass transition
of interacting vortex lines in point-disordered type-II superconductors.Comment: 10 pages, 3 figure
Fractal Droplets in Two Dimensional Spin Glasses
The two-dimensional Edwards-Anderson model with Gaussian bond distribution is
investigated at T=0 with a numerical method. Droplet excitations are directly
observed. It turns out that the averaged volume of droplets is proportional to
l^D with D = 1.80(2) where l is the spanning length of droplets, revealing
their fractal nature. The exponent characterizing the l dependence of the
droplet excitation energy is estimated to be -0.42(4), clearly different from
the stiffness exponent for domain wall excitations.Comment: 4 pages 4 figure
Solvation force for long ranged wall-fluid potentials
The solvation force of a simple fluid confined between identical planar walls
is studied in two model systems with short ranged fluid-fluid interactions and
long ranged wall-fluid potentials decaying as , for
various values of . Results for the Ising spins system are obtained in two
dimensions at vanishing bulk magnetic field by means of the
density-matrix renormalization-group method; results for the truncated
Lennard-Jones (LJ) fluid are obtained within the nonlocal density functional
theory. At low temperatures the solvation force for the Ising film
is repulsive and decays for large wall separations in the same fashion as
the boundary field , whereas for temperatures larger than
the bulk critical temperature is attractive and the asymptotic decay
is . For the LJ fluid system is always
repulsive away from the critical region and decays for large with the the
same power law as the wall-fluid potential. We discuss the influence of the
critical Casimir effect and of capillary condensation on the behaviour of the
solvation force.Comment: 48 pages, 12 figure
Market transactions and hypothetical demand data: A comparative study.
[Dataset available: http://hdl.handle.net/10411/15666]
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