3,267 research outputs found
First exit times of solutions of stochastic differential equations driven by multiplicative Levy noise with heavy tails
In this paper we study first exit times from a bounded domain of a gradient
dynamical system perturbed by a small multiplicative
L\'evy noise with heavy tails. A special attention is paid to the way the
multiplicative noise is introduced. In particular we determine the asymptotics
of the first exit time of solutions of It\^o, Stratonovich and Marcus canonical
SDEs.Comment: 19 pages, 2 figure
When Do People Trust Their Social Groups?
Trust facilitates cooperation and supports positive outcomes in social
groups, including member satisfaction, information sharing, and task
performance. Extensive prior research has examined individuals' general
propensity to trust, as well as the factors that contribute to their trust in
specific groups. Here, we build on past work to present a comprehensive
framework for predicting trust in groups. By surveying 6,383 Facebook Groups
users about their trust attitudes and examining aggregated behavioral and
demographic data for these individuals, we show that (1) an individual's
propensity to trust is associated with how they trust their groups, (2)
smaller, closed, older, more exclusive, or more homogeneous groups are trusted
more, and (3) a group's overall friendship-network structure and an
individual's position within that structure can also predict trust. Last, we
demonstrate how group trust predicts outcomes at both individual and group
level such as the formation of new friendship ties.Comment: CHI 201
Dips in Partial Wave Amplitudes from Final State Interactions
We consider the dip-peak structures in the J=0 partial wave amplitudes for
processes \gamma\gamma\rightarrow W^+W^-~
\mbox{and}~\gamma\gamma,gg\rightarrow t\overline{t} taking into account the
corresponding Born term process and the rescattering process where the
intermediate state is rescattered through the exchange of Higgs resonance state
in the direct channel.Comment: 9 pages, CPP-93-21, 6 figures not include
Global well-posedness for a slightly supercritical surface quasi-geostrophic equation
We use a nonlocal maximum principle to prove the global existence of smooth
solutions for a slightly supercritical surface quasi-geostrophic equation. By
this we mean that the velocity field is obtained from the active scalar
by a Fourier multiplier with symbol , where
is a smooth increasing function that grows slower than as
.Comment: 11 pages, second version with slightly stronger resul
Representing addition and subtraction : learning the formal conventions
The study was designed to test the effects of a structured intervention in teaching children to represent addition and subtraction. In a post-test only control group design, 90 five-year-olds experienced the intervention entitled Bi-directional Translation whilst 90 control subjects experienced typical teaching. Post-intervention testing showed some significant differences between the two groups both in terms of being able to effect the addition and subtraction operations and in being able to determine which operation was appropriate. The results suggest that, contrary to historical practices, children's exploration of real world situations should precede practice in arithmetical symbol manipulation
Heterogeneity, quality, and reputation in an adaptive recommendation model
Recommender systems help people cope with the problem of information
overload. A recently proposed adaptive news recommender model [Medo et al.,
2009] is based on epidemic-like spreading of news in a social network. By means
of agent-based simulations we study a "good get richer" feature of the model
and determine which attributes are necessary for a user to play a leading role
in the network. We further investigate the filtering efficiency of the model as
well as its robustness against malicious and spamming behaviour. We show that
incorporating user reputation in the recommendation process can substantially
improve the outcome
Intermediate Tail Dependence: A Review and Some New Results
The concept of intermediate tail dependence is useful if one wants to
quantify the degree of positive dependence in the tails when there is no strong
evidence of presence of the usual tail dependence. We first review existing
studies on intermediate tail dependence, and then we report new results to
supplement the review. Intermediate tail dependence for elliptical, extreme
value and Archimedean copulas are reviewed and further studied, respectively.
For Archimedean copulas, we not only consider the frailty model but also the
recently studied scale mixture model; for the latter, conditions leading to
upper intermediate tail dependence are presented, and it provides a useful way
to simulate copulas with desirable intermediate tail dependence structures.Comment: 25 pages, 1 figur
Nature of Phase Transitions of Superconducting Wire Networks in a Magnetic Field
We study - characteristics of periodic square Nb wire networks as a
function of temperature in a transverse magnetic field, with a focus on three
fillings 2/5, 1/2, and 0.618 that represent very different levels of
incommensurability. For all three fillings, a scaling behavior of -
characteristics is found, suggesting a finite temperature continuous
superconducting phase transition. The low-temperature - characteristics
are found to have an exponential form, indicative of the domain-wall
excitations.Comment: 5 pages, also available at
http://www.neci.nj.nec.com/homepages/tang.htm
Dialectics and difference: against Harvey's dialectical post-Marxism
David Harvey`s recent book, Justice, nature and the geography of difference (JNGD), engages with a central philosophical debate that continues to dominate human geography: the tension between the radical Marxist project of recent decades and the apparently disempowering relativism and `play of difference' of postmodern thought. In this book, Harvey continues to argue for a revised `post-Marxist' approach in human geography which remains based on Hegelian-Marxian principles of dialectical thought. This article develops a critique of that stance, drawing on the work of Jacques Derrida, Gilles Deleuze and Felix Guattari. I argue that dialectical thinking, as well as Harvey's version of `post-Marxism', has been undermined by the wide-ranging `post-' critique. I suggest that Harvey has failed to appreciate the full force of this critique and the implications it has for `post-Marxist' ontology and epistemology. I argue that `post-Marxism', along with much contemporary human geography, is constrained by an inflexible ontology which excessively prioritizes space in the theory produced, and which implements inflexible concepts. Instead, using the insights of several `post-' writers, I contend there is a need to develop an ontology of `context' leading to the production of `contextual theories'. Such theories utilize flexible concepts in a multilayered understanding of ontology and epistemology. I compare how an approach which produces a `contextual theory' might lead to more politically empowering theory than `post-Marxism' with reference to one of Harvey's case studies in JNGD
Mental Toughness in South African Youth: Relationships With Forgivingness and Attitudes Towards Risk
Young people are particularly vulnerable to health risk behaviors and interpersonal violence, stimulating scholars’ attention towards identifying factors that may reduce the likelihood that these actions will occur. Associated with positive outcomes in a variety of domains, mental toughness in young people might protect them from engaging in potentially deleterious interpersonal or health-risk behaviors, while potentially promoting positive psychological behaviors. Within this framework, the present study investigated the relationships between mental toughness, attitudes towards physical and psychological risk-taking, and trait forgiveness in a sample of 123 (males = 54, females = 69) South African youth (M age = 23.97 years, SD = 4.46). Univariate and multivariate analyses indicated higher levels of mental toughness were associated with being more forgiving, (η2pηp2 = .036), perceiving physical risk-taking more positively (η2pηp2 = .062), but having more negative attitudes towards psychological risk-taking (η2pηp2 = .036). These findings give credence to mental toughness as a psychological characteristic involved in youth risk-taking perceptions and interpersonal functioning. Future research might explore the integration of mental toughness into the development of future youth risk behavior interventions
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