2,324 research outputs found

    The Baryon-Dark Matter Ratio Via Moduli Decay After Affleck-Dine Baryogenesis

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    Low-scale supersymmetry breaking in string motivated theories implies the presence of O(100) TeV scale moduli, which generically lead to a significant modification of the history of the universe prior to Big Bang Nucleosynthesis. Such an approach implies a non-thermal origin for dark matter resulting from scalar decay, where the lightest supersymmetric particle can account for the observed dark matter relic density. We study the further effect of the decay on the baryon asymmetry of the universe, and find that this can satisfactorily address the problem of the over-production of the baryon asymmetry by the Affleck-Dine mechanism in the MSSM. Remarkably, there is a natural connection between the baryon and dark matter abundances today, which leads to a solution of the `Cosmic Coincidence Problem'.Comment: 12 pages, no figure. v2: references adde

    Understanding Divertor Detachment through CRETIN Modeling - a Work in Progress

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    From numerous studies aimed at reducing the divertor target plate incident heat flux or understanding divertor detachment, an abundance of evidence supporting the importance of atomic processes in tokamak plasmas now exists. Through use of a multi-dimensional Non-Local Thermodynamic Equilibrium (NLTE) simulation code named CRETIN [1] this repor

    A two-armed bandit based scheme for accelerated decentralized learning

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    The two-armed bandit problem is a classical optimization problem where a decision maker sequentially pulls one of two arms attached to a gambling machine, with each pull resulting in a random reward. The reward distributions are unknown, and thus, one must balance between exploiting existing knowledge about the arms, and obtaining new information. Bandit problems are particularly fascinating because a large class of real world problems, including routing, QoS control, game playing, and resource allocation, can be solved in a decentralized manner when modeled as a system of interacting gambling machines. Although computationally intractable in many cases, Bayesian methods provide a standard for optimal decision making. This paper proposes a novel scheme for decentralized decision making based on the Goore Game in which each decision maker is inherently Bayesian in nature, yet avoids computational intractability by relying simply on updating the hyper parameters of sibling conjugate priors, and on random sampling from these posteriors. We further report theoretical results on the variance of the random rewards experienced by each individual decision maker. Based on these theoretical results, each decision maker is able to accelerate its own learning by taking advantage of the increasingly more reliable feedback that is obtained as exploration gradually turns into exploitation in bandit problem based learning. Extensive experiments demonstrate that the accelerated learning allows us to combine the benefits of conservative learning, which is high accuracy, with the benefits of hurried learning, which is fast convergence. In this manner, our scheme outperforms recently proposed Goore Game solution schemes, where one has to trade off accuracy with speed. We thus believe that our methodology opens avenues for improved performance in a number of applications of bandit based decentralized decision making

    Cross-cultural effects of color, but not morphological masculinity, on perceived attractiveness of men's faces

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    This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 ElsevierMuch attractiveness research has focused on face shape. The role of masculinity (which for adults is thought to be a relatively stable shape cue to developmental testosterone levels) in male facial attractiveness has been examined, with mixed results. Recent work on the perception of skin color (a more variable cue to current health status) indicates that increased skin redness, yellowness, and lightness enhance apparent health. It has been suggested that stable cues such as masculinity may be less important to attractiveness judgments than short-term, more variable health cues. We examined associations between male facial attractiveness, masculinity, and skin color in African and Caucasian populations. Masculinity was not found to be associated with attractiveness in either ethnic group. However, skin color was found to be an important predictor of attractiveness judgments, particularly for own-ethnicity faces. Our results suggest that more plastic health cues, such as skin color, are more important than developmental cues such as masculinity. Further, unfamiliarity with natural skin color variation in other ethnic groups may limit observers' ability to utilize these color cues

    Personal identity (de)formation among lifestyle travellers: A double-edged sword?

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    This article explores the personal identity work of lifestyle travellers – individuals for whom extended leisure travel is a preferred lifestyle that they return to repeatedly. Qualitative findings from in-depth semi-structured interviews with lifestyle travellers in northern India and southern Thailand are interpreted in light of theories on identity formation in late modernity that position identity as problematic. It is suggested that extended leisure travel can provide exposure to varied cultural praxes that may contribute to a sense of social saturation. Whilst a minority of the respondents embraced a saturation of personal identity in the subjective formation of a cosmopolitan cultural identity, several of the respondents were paradoxically left with more identity questions than answers as the result of their travels

    A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship

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    Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship

    Supersymmetric Relations Among Electromagnetic Dipole Operators

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    Supersymmetric contributions to all leptonic electromagnetic dipole operators have essentially identical diagramatic structure. With approximate slepton universality this allows the muon anomalous magnetic moment to be related to the electron electric dipole moment in terms of supersymmetric phases, and to radiative flavor changing lepton decays in terms of small violations of slepton universality. If the current discrepancy between the measured and Standard Model values of the muon anomalous magnetic moment is due to supersymmetry, the current bound on the electron electric dipole moment then implies that the phase of the electric dipole operator is less than 2×1032 \times 10^{-3}. Likewise the current bound on μeγ\mu \to e \gamma decay implies that the fractional selectron-smuon mixing in the left-left mass squared matrix, \delta m_{\smuon \selectron}^2 / m_{\slepton}^2, is less than 10410^{-4}. These relations and constraints are fairly insensitive to details of the superpartner spectrum for moderate to large tanβ\tan \beta.Comment: Latex, 38 pages, 2 figure

    Travel, tourism, climate change and behavioral change: travelers’ perspectives from a developing country, Nigeria

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    While studies have examined people's understanding of climate change and its relationship to tourism, these focus largely on developed country populations. Much future tourism growth will come from developing countries following economic development; often countries where climate change will be strongly felt. Do tourists from developing countries have the same knowledge gaps about travel, tourism, and climate change as in the developed world? Will behavioral change policies be successful in encouraging more environmentally friendly approaches to climate change and tourism in developing countries? This paper presents findings from 20 in-depth interviews with active Nigerian tourists, analyzing their understanding of climate change, the links known, or not, between their travel and climate change, and their willingness to change their tourism patterns. Understanding of climate change was limited and there was conceptual confusion. Participants did not view their own travel as a cause of climate change and many were embedded in air travel practice. Participants were unwilling to change their tourism patterns to reduce their contribution to climate change. Significant structural barriers limit low carbon tourism travel in Nigeria (and other developing countries), including reliability, availability safety, and speed. Behavioral change will be difficult to achieve

    Targeting FLT3 in primary MLL-gene-rearranged infant acute lymphoblastic leukemia

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    Acute lymphoblastic leukemia (ALL) in infants is characterized by rearrangements of the mixed lineage leukemia (MLL) gene, drug resistance, and a poor treatment outcome. Therefore, novel therapeutic strategies are needed to improve prognosis. Recently, we showed that FLT3 is highly expressed in MLL rearranged ALL (MLL). Here we demonstrate FLT3 expression in infants with MLL (n = 41) to be significantly higher compared to both infant (n = 8; P < .001) and noninfant patients with ALL (n = 23; P = .001) carrying germline MLL genes. Furthermore, leukemic cells from infants with MLL were significantly more sensitive to the Fms-like tyrosine kinase 3 (FLT3) inhibitor PKC412 (N-benzoyl staurosporine) than noninfant ALL cells, and at least as sensitive as internal tandem duplication-positive (ITD+) AML cells. Surprisingly, activation loop mutations only occurred in about 3% (1 of 36) of the cases and no FLT3/ITDs were observed. However, measuring FLT3 phosphorylation in infants with MLL expressing varying levels of wild-type FLT3 revealed that high-level FLT3 expression is associated with ligand-independent FLT3 activation. This suggests that infant MLL cells displaying activated FLT3 as a result of overexpression can be targeted by FLT3 inhibitors such as PKC412. However, at concentrations of PKC412 minimall
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