40,320 research outputs found
The analytic torsion of the finite metric cone over a compact manifold
We give an explicit formula for the analytic torsion of the finite
metric cone over an oriented compact connected Riemannian manifold. We provide
an interpretation of the different factors appearing in this formula. We prove
that the analytic torsion of the cone is the finite part of the limit obtained
collapsing one of the boundaries, of the ratio of the analytic torsion of the
frustum to a regularising factor. We show that the regularising factor comes
from the set of the non square integrable eigenfunctions of the Laplace
Beltrami operator on the cone.Comment: To appear in Journal of the Mathematical Society of Japa
Direct sampling of complex landscapes at low temperatures: the three-dimensional +/-J Ising spin glass
A method is presented, which allows to sample directly low-temperature
configurations of glassy systems, like spin glasses. The basic idea is to
generate ground states and low lying excited configurations using a heuristic
algorithm. Then, with the help of microcanonical Monte Carlo simulations, more
configurations are found, clusters of configurations are determined and
entropies evaluated. Finally equilibrium configuration are randomly sampled
with proper Gibbs-Boltzmann weights.
The method is applied to three-dimensional Ising spin glasses with +- J
interactions and temperatures T<=0.5. The low-temperature behavior of this
model is characterized by evaluating different overlap quantities, exhibiting a
complex low-energy landscape for T>0, while the T=0 behavior appears to be less
complex.Comment: 9 pages, 7 figures, revtex (one sentence changed compared to v2
Is there a role for thoracic aortic calcium to fine-tune cardiovascular risk prediction?
Screening asymptomatic subjects to streamline measures for the prevention of cardiovascular events remains a major challenge. The established primary prevention risk-scoring methods use equations derived from large prospective cohort studies, but further fine-tuning of cardiovascular risk assessment remains important as 25 % of individuals with low estimated risk may experience cardiac events. Independent studies provided evidence that extended risk assessment using coronary artery calcium quantification may improve risk stratification as it can lead to reclassification of persons at increased risk. Particularly in intermediate-risk subjects, coronary artery calcium scoring can help to correctly identify individuals at highest risk. Data on the extent of calcification of the ascending and descending thoracic aorta might be useful for additional cardiovascular risk stratification. Future analyses and studies will be required to answer the question of whether the implementation of such data may allow further fine-tuning of cardiovascular risk prediction in specific subpopulations—for instance in women or men with an increased risk of stroke and/or symptomatic peripheral vascular diseas
The syntax of existential sentences in Serbian
Freeze (1992) argued on the basis of data from several different languages that there is a close relationship between existential sentences (stating the existence of an entity) and locative sentences (stating the location of an entity). Freeze (1992) proposes that they are both derived from the same base structure and that the surface differences are rather due to the distinct information structures.This paper argues against this position with the data from Serbian existentials, which show clear syntactic differences from the locatives. Thus, the close relationship between existential and locative sentences that Freeze (1992) observes is conceptual, but not (necessarily) part of the syntax of the language. In order to account for the data, we propose that existential sentences originate from a different syntactic predication structure than the locative ones. The existential meaning arises, as we will show, from the interaction of this predication structure with the structure and meaning of the noun phrase
Critical behavior of the Random-Field Ising Magnet with long range correlated disorder
We study the correlated-disorder driven zero-temperature phase transition of
the Random-Field Ising Magnet using exact numerical ground-state calculations
for cubic lattices. We consider correlations of the quenched disorder decaying
proportional to r^a, where r is the distance between two lattice sites and a<0.
To obtain exact ground states, we use a well established mapping to the
graph-theoretical maximum-flow problem, which allows us to study large system
sizes of more than two million spins. We use finite-size scaling analyses for
values a={-1,-2,-3,-7} to calculate the critical point and the critical
exponents characterizing the behavior of the specific heat, magnetization,
susceptibility and of the correlation length close to the critical point. We
find basically the same critical behavior as for the RFIM with delta-correlated
disorder, except for the finite-size exponent of the susceptibility and for the
case a=-1, where the results are also compatible with a phase transition at
infinitesimal disorder strength.
A summary of this work can be found at the papercore database at
www.papercore.org.Comment: 9 pages, 13 figure
Gaussian quantum fluctuations in interacting many particle systems
We consider a many particle quantum system, in which each particle interacts
only with its nearest neighbours. Provided that the energy per particle has an
upper bound, we show, that the energy distribution of almost every product
state becomes a Gaussian normal distribution in the limit of infinite number of
particles. We indicate some possible applications.Comment: 10 pages, formulation made mathematically more precise, two examples
added, accepted for publication in Letters in Mathematical Physic
Prussian Blue-coated interdigitated array electrodes for possible analytical application
Thin films of iron(III) hexacyanoferrate(II) (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes, yielding systems which can be considered as chemiresistors in sensing alkali metal ion concentrations in an adjacent electrolyte. This is due to the fact that the conductivity of the film being measured by a steady-state current on application of a voltage to the two-fingered electrodes of the IDA depends on both the redox stare of the film and the cation concentration in the electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali metal ions and for mixtures of alkali metal ions, the possibilities of analytical application were elucidated. In addition, by using the methods of staircase coulometry and scanning conductivity, the electron diffusion coefficient De was determined as a function of the redox state of Prussian Blue. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali metal ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs
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