61,574 research outputs found

    New Slant on the EPR-Bell Experiment

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    The best case for thinking that quantum mechanics is nonlocal rests on Bell's Theorem, and later results of the same kind. However, the correlations characteristic of EPR-Bell (EPRB) experiments also arise in familiar cases elsewhere in QM, where the two measurements involved are timelike rather than spacelike separated; and in which the correlations are usually assumed to have a local causal explanation, requiring no action-at-a-distance. It is interesting to ask how this is possible, in the light of Bell's Theorem. We investigate this question, and present two options. Either (i) the new cases are nonlocal, too, in which case action-at-a-distance is more widespread in QM than has previously been appreciated (and does not depend on entanglement, as usually construed); or (ii) the means of avoiding action-at-a-distance in the new cases extends in a natural way to EPRB, removing action-at-a-distance in these cases, too. There is a third option, viz., that the new cases are strongly disanalogous to EPRB. But this option requires an argument, so far missing, that the physical world breaks the symmetries which otherwise support the analogy. In the absence of such an argument, the orthodox combination of views -- action-at-a-distance in EPRB, but local causality in its timelike analogue -- is less well established than it is usually assumed to be.Comment: 26 pages, 7 figures; extensively revised for resubmissio

    Is the Water Sector Lagging behind Education and Health on Aid Effectiveness? Lessons from Bangladesh, Ethiopia and Uganda

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    A study in three countries (Bangladesh, Ethiopia and Uganda) assessed progress against the Paris Principles for Aid Effectiveness (AE) in three sectors – water, health and education – to test the assumption that the water sector is lagging behind. The findings show that it is too simplistic to say that the water sector is lagging, although this may well be the case in some countries. The study found that wider governance issues are more important for AE than having in place sector-specific mechanics such as Sector-Wide Approaches alone. National political leadership and governance are central drivers of sector AE, while national financial and procurement systems and the behaviour of actors who have not signed up to the Paris Principles – at both national and global levels – have implications for progress that cut across sectors. Sectors and sub-sectors do nonetheless have distinct features that must be considered in attempting to improve sector-level AE. In light of these findings, using political economy approaches to better understand and address governance and strengthening sector-level monitoring is recommended as part of efforts to improve AE and development results in the water sector

    Conserved mass models with stickiness and chipping

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    We study a chipping model in one dimensional periodic lattice with continuous mass, where a fixed fraction of the mass is chipped off from a site and distributed randomly among the departure site and its neighbours; the remaining mass sticks to the site. In the asymmetric version, the chipped off mass is distributed among the site and the right neighbour, whereas in the symmetric version the redistribution occurs among the two neighbours. The steady state mass distribution of the model is obtained using a perturbation method for both parallel and random sequential updates. In most cases, this perturbation theory provides a steady state distribution with reasonable accuracy.Comment: 17 pages, 4 eps figure

    Phase Transition in the ABC Model

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    Recent studies have shown that one-dimensional driven systems can exhibit phase separation even if the dynamics is governed by local rules. The ABC model, which comprises three particle species that diffuse asymmetrically around a ring, shows anomalous coarsening into a phase separated steady state. In the limiting case in which the dynamics is symmetric and the parameter qq describing the asymmetry tends to one, no phase separation occurs and the steady state of the system is disordered. In the present work we consider the weak asymmetry regime q=exp(β/N)q=\exp{(-\beta/N)} where NN is the system size and study how the disordered state is approached. In the case of equal densities, we find that the system exhibits a second order phase transition at some nonzero βc\beta_c. The value of βc=2π3\beta_c = 2 \pi \sqrt{3} and the optimal profiles can be obtained by writing the exact large deviation functional. For nonequal densities, we write down mean field equations and analyze some of their predictions.Comment: 18 pages, 3 figure

    Numerical Evidence for Divergent Burnett Coefficients

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    In previous papers [Phys. Rev. A {\bf 41}, 4501 (1990), Phys. Rev. E {\bf 18}, 3178 (1993)], simple equilibrium expressions were obtained for nonlinear Burnett coefficients. A preliminary calculation of a 32 particle Lennard-Jones fluid was presented in the previous paper. Now, sufficient resources have become available to address the question of whether nonlinear Burnett coefficients are finite for soft spheres. The hard sphere case is known to have infinite nonlinear Burnett coefficients (ie a nonanalytic constitutive relation) from mode coupling theory. This paper reports a molecular dynamics caclulation of the third order nonlinear Burnett coefficient of a Lennard-Jones fluid undergoing colour flow, which indicates that this term is diverges in the thermodynamic limit.Comment: 12 pages, 9 figure

    Identifying optimal feature transforms for classification and prediction in biological systems: recovering receptive field vectors from sparse recordings

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    With biological systems it is often hard to adequately sample the entire input space. With sensory neural systems this can be a particularly acute problem, with very high dimensional natural inputs and typically sparse spiking outputs. Here we present an information theory based approach to analyse spiking data of an early sensory pathway, demonstrated on retinal ganglion cells (RGC) responding to natural visual scene stimuli (Katz et al., 2016). We used a non-parametric technique based on the concept of mutual information (MI), in particular, Quadratic Mutual Information (QMI). The QMI allowed us to very efficiently search the high dimensional space formed by the visual input for a much smaller dimensional subspace of Receptive Field Vectors (RFV). RFVs give the most information about the response of the cell to natural stimuli. This approach allows us to identify the RFVs far more efficiently using limited data as we can search the complete stimulus space for multiple vectors simultaneously. The RFVs were also used to predict the RGCs’ responses to any natural stimuli. Another suitable area of application of this algorithm is in diagnostic inference. Currently we are adapting the method to be used for identifying the cancer markers in the volatile organic compounds present in exhaled breath. Once the maximally informative features are established they can be used for diagnostic predictions on new breath samples. Preliminary results of the breathomics analysis will be discussed at the conference. There are several other potential applications such as multiclass categorisation for bacterial strains using ISFET arrays for DNA sequencing. This algorithm can be part of a rapid point-of-care device for identifying the specific infectious agents and recommending appropriate antibiotics. Here we will focus on presenting the algorithm using the example of RFVs of RGCs

    Condensation Transitions in Two Species Zero-Range Process

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    We study condensation transitions in the steady state of a zero-range process with two species of particles. The steady state is exactly soluble -- it is given by a factorised form provided the dynamics satisfy certain constraints -- and we exploit this to derive the phase diagram for a quite general choice of dynamics. This phase diagram contains a variety of new mechanisms of condensate formation, and a novel phase in which the condensate of one of the particle species is sustained by a `weak' condensate of particles of the other species. We also demonstrate how a single particle of one of the species (which plays the role of a defect particle) can induce Bose-Einstein condensation above a critical density of particles of the other species.Comment: 17 pages, 4 Postscript figure

    The perception of familiar and unfamiliar accents by bilingual and monolingual children

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    In large urban cities, children typically grow-up in a diverse multicultural environment. Depending on their local language environment, children are often exposed to regional as well as foreign-accents. This study investigated whether children’s accent processing is affected by the variability in their ambient language environment. English monolingual and Sylheti-English bilingual children were assessed on their ability to identify sentences in three accent conditions: London-English (familiar to all), Sylheti-accented English (only familiar to the bilinguals), Spanishaccented English (unfamiliar to all). All children were most accurate in the London-English accent condition, however the groups differed with their dominant familiar accent: the monolinguals were more accurate at recalling the London-English sentences than the bilinguals, and the bilinguals were more accurate in the Sylheti-accented condition than the monolinguals. The results suggest that variation in linguistic experience in early life, give rise to differences in the processing of familiar and unfamiliar accented speech

    To what extent does severity of loneliness vary among different mental health diagnostic groups: A cross-sectional study.

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    Loneliness is a common and debilitating problem in individuals with mental health disorders. However, our knowledge on severity of loneliness in different mental health diagnostic groups and factors associated with loneliness is poor, thus limiting the ability to target and improve loneliness interventions. The current study investigated the association between diagnoses and loneliness and explored whether psychological and social factors were related to loneliness. This study employed a cross-sectional design using data from a completed study which developed a measure of social inclusion. It included 192 participants from secondary, specialist mental health services with a primary diagnosis of psychotic disorders (n = 106), common mental disorders (n = 49), or personality disorders (n = 37). The study explored differences in loneliness between these broad diagnostic groups, and the relationship to loneliness of: affective symptoms, social isolation, perceived discrimination, and internalized stigma. The study adhered to the STROBE checklist for observational research. People with common mental disorders (MD = 3.94, CI = 2.15 to 5.72, P < 0.001) and people with personality disorders (MD = 4.96, CI = 2.88 to 7.05, P < 0.001) reported higher levels of loneliness compared to people with psychosis. These differences remained significant after adjustment for all psychological and social variables. Perceived discrimination and internalized stigma were also independently associated with loneliness and substantially contributed to a final explanatory model. The severity of loneliness varies between different mental health diagnostic groups. Both people with common mental disorders and personality disorders reported higher levels of loneliness than people with psychosis. Addressing perceived mental health discrimination and stigma may help to reduce loneliness
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