1,576 research outputs found
Gravitation Physics at BGPL
We report progress on a program of gravitational physics experiments using
cryogenic torsion pendula undergoing large-amplitude torsion oscillation. This
program includes tests of the gravitational inverse square law and of the weak
equivalence principle. Here we describe our ongoing search for
inverse-square-law violation at a strength down to of standard
gravity. The low-vibration environment provided by the Battelle Gravitation
Physics Laboratory (BGPL) is uniquely suited to this study.Comment: To be published in The Proceedings of the Francesco Melchiorri
Memorial Conference as a special issue of New Astronomy Review
On Stable Pareto Laws in a Hierarchical Model of Economy
This study considers a model of the income distribution of agents whose
pairwise interaction is asymmetric and price-invariant. Asymmetric transactions
are typical for chain-trading groups who arrange their business such that
commodities move from senior to junior partners and money moves in the opposite
direction. The price-invariance of transactions means that the probability of a
pairwise interaction is a function of the ratio of incomes, which is
independent of the price scale or absolute income level. These two features
characterize the hierarchical model. The income distribution in this class of
models is a well-defined double-Pareto function, which possesses Pareto tails
for the upper and lower incomes. For gross and net upper incomes, the model
predicts definite values of the Pareto exponents, and , which are stable with respect to quantitative variation of the
pair-interaction. The Pareto exponents are also stable with respect to the
choice of a demand function within two classes of status-dependent behavior of
agents: linear demand (, ) and unlimited slowly
varying demand (). For the sigmoidal demand that
describes limited returns, , with some
satisfying a transcendental equation. The low-income distribution
may be singular or vanishing in the neighborhood of the minimal income; in any
case, it is -integrable and its Pareto exponent is given explicitly.
The theory used in the present study is based on a simple balance equation
and new results from multiplicative Markov chains and exponential moments of
random geometric progressions.Comment: 23 pages, 10 figure
A mechanism to derive multi-power law functions: an application in the econophysics framework
It is generally recognized that economical systems, and more in general
complex systems, are characterized by power law distributions. Sometime, these
distributions show a changing of the slope in the tail so that, more
appropriately, they show a multi-power law behavior. We present a method to
derive analytically a two-power law distribution starting from a single power
law function recently obtained, in the frameworks of the generalized
statistical mechanics based on the Sharma-Taneja-Mittal information measure. In
order to test the method, we fit the cumulative distribution of personal income
and gross domestic production of several countries, obtaining a good agreement
for a wide range of data.Comment: 10pages, 3 figures. Presented at Int. Conf. on Application of Physics
in Financial Analisys (APFA5), June 29 - July 1, 2006 Torino, Ital
Broken scaling in the Forest Fire Model
We investigate the scaling behavior of the cluster size distribution in the
Drossel-Schwabl Forest Fire model (DS-FFM) by means of large scale numerical
simulations, partly on (massively) parallel machines. It turns out that simple
scaling is clearly violated, as already pointed out by Grassberger [P.
Grassberger, J. Phys. A: Math. Gen. 26, 2081 (1993)], but largely ignored in
the literature. Most surprisingly the statistics not seems to be described by a
universal scaling function, and the scale of the physically relevant region
seems to be a constant. Our results strongly suggest that the DS-FFM is not
critical in the sense of being free of characteristic scales.Comment: 9 pages in RevTEX4 format (9 figures), submitted to PR
Lyapunov exponents for products of complex Gaussian random matrices
The exact value of the Lyapunov exponents for the random matrix product with each , where
is a fixed positive definite matrix and a complex Gaussian matrix with entries standard complex normals, are
calculated. Also obtained is an exact expression for the sum of the Lyapunov
exponents in both the complex and real cases, and the Lyapunov exponents for
diffusing complex matrices.Comment: 15 page
Teachers' classroom feedback: still trying to get it right
This article examines feedback traditionally given by teachers in schools. Such feedback tends to focus on children's acquisition and retrieval of externally prescribed knowledge which is then assessed against mandated tests. It suggests that, from a sociocultural learning perspective, feedback directed towards such objectives may limit children's social development. In this article, I draw on observation and interview data gathered from a group of 27 9- to 10-year olds in a UK primary school. These data illustrate the children's perceived need to conform to, rather than negotiate, the teacher's feedback comments. They highlight the children's sense that the teacher's feedback relates to school learning but not to their own interests. The article also includes alternative examples of feedback which draw on children's own inquiries and which relate to the social contexts within which, and for whom, they act. It concludes by suggesting that instead of looking for the right answer to the question of what makes teachers' feedback effective in our current classrooms, a more productive question might be how a negotiation can be opened up among teachers and learners themselves, about how teachers' feedback could support children's learning most appropriately
Jointly embedding entities and text with distant supervision
Learning representations for knowledge base entities and concepts is becoming increasingly important for NLP applications. However, recent entity embedding methods have relied on structured resources that are expensive to create for new domains and corpora. We present a distantly-supervised method for jointly learning embeddings of entities and text from an unnanotated corpus, using only a list of mappings between entities and surface forms. We learn embeddings from open-domain and biomedical corpora, and compare against prior methods that rely on human-annotated text or large knowledge graph structure. Our embeddings capture entity similarity and relatedness better than prior work, both in existing biomedical datasets and a new Wikipedia-based dataset that we release to the community. Results on analogy completion and entity sense disambiguation indicate that entities and words capture complementary information that can be effectively combined for downstream use
Positive temperature versions of two theorems on first-passage percolation
The estimates on the fluctuations of first-passsage percolation due to
Talagrand (a tail bound) and Benjamini--Kalai--Schramm (a sublinear variance
bound) are transcribed into the positive-temperature setting of random
Schroedinger operators.Comment: 15 pp; to appear in GAFA Seminar Note
Towards a formalism for mapping the spacetimes of massive compact objects: Bumpy black holes and their orbits
Observations have established that extremely compact, massive objects are
common in the universe. It is generally accepted that these objects are black
holes. As observations improve, it becomes possible to test this hypothesis in
ever greater detail. In particular, it is or will be possible to measure the
properties of orbits deep in the strong field of a black hole candidate (using
x-ray timing or with gravitational-waves) and to test whether they have the
characteristics of black hole orbits in general relativity. Such measurements
can be used to map the spacetime of a massive compact object, testing whether
the object's multipoles satisfy the strict constraints of the black hole
hypothesis. Such a test requires that we compare against objects with the
``wrong'' multipole structure. In this paper, we present tools for constructing
bumpy black holes: objects that are almost black holes, but that have some
multipoles with the wrong value. The spacetimes which we present are good deep
into the strong field of the object -- we do not use a large r expansion,
except to make contact with weak field intuition. Also, our spacetimes reduce
to the black hole spacetimes of general relativity when the ``bumpiness'' is
set to zero. We propose bumpy black holes as the foundation for a null
experiment: if black hole candidates are the black holes of general relativity,
their bumpiness should be zero. By comparing orbits in a bumpy spacetime with
those of an astrophysical source, observations should be able to test this
hypothesis, stringently testing whether they are the black holes of general
relativity. (Abridged)Comment: 16 pages + 2 appendices + 3 figures. Submitted to PR
Effects of total and regional fat loss on plasma CRP and IL-6 in overweight and obese, older adults with knee osteoarthritis
SummaryObjectiveTo describe associations between total and regional body fat mass loss and reduction of systemic levels of inflammation (C-reactive protein (CRP) and interleukin-6 (IL-6)) in obese, older adults with osteoarthritis (OA), undergoing intentional weight loss.DesignData come from a single-blind, 18-month, randomized controlled trial in adults (age: 65.6 ± 6.2; Body mass index (BMI): 33.6 ± 3.7) with knee OA. Participants were randomized to diet-induced weight loss plus exercise (D + E; n = 150), diet-induced weight loss-only (D; n = 149), or exercise-only (E; n = 151). Total body and region-specific (abdomen and thigh) fat mass were measured at baseline and 18 months. High-sensitivity CRP and IL-6 were measured at baseline, six and 18 months. Intervention effects were assessed using mixed models and associations between inflammation and adiposity were compared using logistic and mixed linear regression models.ResultsIntentional total body fat mass reduction was associated with significant reductions in log-adjusted CRP (β = 0.06 (95% CI = 0.04, 0.08) mg/L) and IL-6 (β = 0.02 (95% CI = 0.01, 0.04) pg/mL). Loss of abdominal fat volume was also associated with reduced inflammation, independent of total body fat mass; although models containing measures of total adiposity yielded the best fit. The odds of achieving clinically desirable levels of CRP (<3.0 mg/L) and IL-6 (<2.5 pg/mL) were 3.8 (95% CI = 1.6, 8.9) and 2.2 (95% CI = 1.1, 4.6), respectively, with 5% total weight and fat mass loss.ConclusionsAchievement of clinically desirable levels of CRP and IL-6 more than double with intentional 5% loss of total body weight and fat mass. Global, rather than regional, measures of adiposity are better predictors of change in inflammatory burden.Clinical Trial Registration NumberNCT00381290
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