11,041 research outputs found
Form factors of twist fields in the lattice Dirac theory
We study U(1) twist fields in a two-dimensional lattice theory of massive
Dirac fermions. Factorized formulas for finite-lattice form factors of these
fields are derived using elliptic parametrization of the spectral curve of the
model, elliptic determinant identities and theta functional interpolation. We
also investigate the thermodynamic and the infinite-volume scaling limit, where
the corresponding expressions reduce to form factors of the exponential fields
of the sine-Gordon model at the free-fermion point.Comment: 20 pages, 2 figure
Learning a spin glass: determining Hamiltonians from metastable states
We study the problem of determining the Hamiltonian of a fully connected
Ising Spin Glass of units from a set of measurements, whose sizes needs to
be bits. The student-teacher scenario, used to study learning
in feed-forward neural networks, is here extended to spin systems with
arbitrary couplings. The set of measurements consists of data about the local
minima of the rugged energy landscape. We compare simulations and analytical
approximations for the resulting learning curves obtained by using different
algorithms.Comment: 5 pages, 1 figure, to appear in Physica
Properties of the solvation force of a two-dimensional Ising strip in scaling regimes
We consider d=2 Ising strip with surface fields acting on boundary spins.
Using the properties of the transfer matrix spectrum we identify two
pseudotransition temperatures and show that they satisfy similar scaling
relations as expected for real transition temperatures in strips with d>2. The
solvation force between the boundaries of the strip is analysed as a function
of temperature, surface fields and the width of the strip. For large widths the
solvation force can be described by scaling functions in three different
regimes: in the vicinity of the critical wetting temperature of 2D
semi-infinite system, in the vicinity of the bulk critical temperature, and in
the regime of weak surface fields where the critical wetting temperature tends
towards the bulk critical temperature. The properties of the relevant scaling
functions are discussed
Splitting hairs of the three charge black hole
We construct the large radius limit of the metric of three charge supertubes
and three charge BPS black rings by using the fact that supertubes preserve the
same supersymmetries as their component branes. Our solutions reproduce a few
of the properties of three charge supertubes found recently using the Born
Infeld description. Moreover, we find that these solutions pass a number of
rather nontrivial tests which they should pass if they are to describe some of
the hair of three charge black holes and three charge black rings.Comment: 15 pages, LaTeX, v2 minor correction
Spin operator matrix elements in the quantum Ising chain: fermion approach
Using some modification of the standard fermion technique we derive
factorized formula for spin operator matrix elements (form-factors) between
general eigenstates of the Hamiltonian of quantum Ising chain in a transverse
field of finite length. The derivation is based on the approach recently used
to derive factorized formula for Z_N-spin operator matrix elements between
ground eigenstates of the Hamiltonian of the Z_N-symmetric superintegrable
chiral Potts quantum chain. The obtained factorized formulas for the matrix
elements of Ising chain coincide with the corresponding expressions obtained by
the Separation of Variables Method.Comment: 19 page
Counting Supertubes
The quantum states of the supertube are counted by directly quantizing the
linearized Born-Infeld action near the round tube. The result is an entropy , in accord with conjectures in the
literature. As a result, supertubes may be the generic D0-F1 bound state. Our
approach also shows directly that supertubes are marginal bound states with a
discrete spectrum. We also discuss the relation to recent suggestions of Mathur
et al involving three-charge black holes.Comment: 15 pages, v2: reference corrected; v3: few corrections and explicit
derivation of a relation are added to appendix
Supertube domain-walls and elimination of closed time-like curves in string theory
We show that some novel physics of supertubes removes closed time-like curves
from many supersymmetric spaces which naively suffer from this problem. The
main claim is that supertubes naturally form domain-walls, so while analytical
continuation of the metric would lead to closed time-like curves, across the
domain-wall the metric is non-differentiable, and the closed time-like curves
are eliminated. In the examples we study the metric inside the domain-wall is
always of the G\"odel type, while outside the shell it looks like a localized
rotating object, often a rotating black hole. Thus this mechanism prevents the
appearance of closed time-like curves behind the horizons of certain rotating
black holes.Comment: 22 pages, JHEP3 class. V2: Some corrections and clariffications,
references added. V3: more corrections to formulas, results unchanged. V4:
minor typos, as published in PR
Comparison of Commercial and Self-Initiated Weight Loss Programs in People With Prediabetes: A Randomized Control Trial
To determine if a widely available weight-management program (Weight Watchers) could achieve sufficient weight loss in persons with prediabetes compared with a Diabetes Prevention Program-based individual counseling program supported by National Diabetes Education Program materials.
METHODS:
We conducted an individual, randomized intervention trial in Indianapolis, Indiana, in 2013 to 2014, in 225 persons with prediabetes. We compared the Weight Watchers weight-management program (n = 112) with Your Game Plan to Prevent Type 2 Diabetes, a program developed by the National Diabetes Education Program. Outcomes were weight and metabolic markers measured at baseline, 6 months, and 12 months.
RESULTS:
Intervention participants lost significantly more weight than controls at 6 months (5.5% vs 0.8%) and 12 months (5.5% vs 0.2%; both P < .001). The intervention group also had significantly greater improvements in hemoglobin A1c and high-density lipoprotein cholesterol level than did controls.
CONCLUSIONS:
A large weight-management program is effective for achieving lifestyle changes associated with diabetes prevention. Such programs could significantly increase the availability of diabetes prevention programs worldwide making an immediate and significant public health impact
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